Tanya

 

 

 

 

 

 

 

 

TANYA'S

COMPREHENSIVE GUIDE TO

FELINE CHRONIC KIDNEY DISEASE

24 July 2000 - 24 July 2020

Twenty years online!

(Not tax deductible since I am a private individual)

 

 

 

 

 

DIAGNOSIS: BLOOD CHEMISTRY PANEL

 

ON THIS PAGE:


Kidney Values: GFR, BUN/urea, Creatinine, SDMA, Azotaemia, Uraemia


Potassium and Sodium


Magnesium


Total Protein: Albumin, Globulin and the AG Ratio


Other: CK/CPK, Cholesterol, Glucose, ALT or GPT, Amylase


 

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WHAT IS CKD?


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Acute Kidney Injury


 

KEY ISSUES: PROLONGING LIFE


Phosphorus Control


Hypertension

(High Blood Pressure)


Proteinuria


Anaemia


Potassium Imbalances


Pyelonephritis (Kidney Infections) and Urinary Tract Infections NEW


Metabolic Acidosis


Kidney Stones


 

KEY ISSUES: HELPING YOUR CAT FEEL BETTER


Nausea, Vomiting, Appetite Loss and Excess Stomach Acid


Maintaining Hydration


The B Vitamins (Including Methylcobalamin)


Constipation


 

CAT FOOD DATA


Ways of Assessing Food Content, Including What is Dry Matter Analysis


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SYMPTOMS


Important: Crashing


Alphabetical List of Symptoms and Treatments


Fluid and Urinary  Imbalances (Dehydration, Overhydration and Urinary Issues)


Waste Product Regulation Imbalances (Vomiting, Appetite Loss, Excess Stomach Acid, Gastro-intestinal Problems, Mouth Ulcers Etc.)


Phosphorus and Calcium Imbalances


Miscellaneous Symptoms (Pain, Hiding Etc.)


 

DIAGNOSIS: WHAT DO ALL THE TEST RESULTS MEAN?


Early Detection


Blood Chemistry: Kidney Function, Potassium, Other Tests (ALT, Amylase, (Cholesterol, Etc.)


Calcium, Phosphorus, Parathyroid Hormone (PTH) and Secondary Hyperparathyroidism


Complete Blood Count (CBC): Red and White Blood Cells: Anaemia and Infection


Urinalysis (Urine Tests)


Other Tests: Ultrasound, Biopsy, X-rays etc.


Renomegaly (Enlarged Kidneys)


Which Tests to Have and Frequency of Testing


Factors that Affect Test Results


Normal Ranges


International and US Measuring Systems


 

TREATMENTS


Which Treatments are Essential


Fluid and Urinary Issues (Fluid Retention, Infections, Incontinence, Proteinuria)


Waste Product Regulation (Mouth Ulcers, GI Bleeding, Antioxidants, Adsorbents, Azodyl, Astro's CRF Oil)


Phosphorus, Calcium and Secondary Hyperparathyroidism (Calcitriol)


Phosphorus Binders


Steroids, Stem Cell Transplants and Kidney Transplants


Antibiotics and Painkillers


Holistic Treatments (Including Slippery Elm Bark)


ESAs (Aranesp, Epogen etc.) for Severe Anaemia


General Health Issues in a CKD Cat: Fleas, Arthritis, Dementia, Vaccinations


Tips on Medicating Your Cat


Obtaining Supplies Cheaply in the UK, USA and Canada


Working with Your Vet and Recordkeeping


 

DIET & NUTRITION


Nutritional Requirements of CKD Cats


The B Vitamins (Including Methylcobalamin)


What to Feed (and What to Avoid)


Persuading Your Cat to Eat


2007 Food Recall USA


 

FLUID THERAPY


Oral Fluids


Intravenous Fluids


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How to Give Subcutaneous Fluids with a Giving Set


How to Give Subcutaneous Fluids with a Syringe


Subcutaneous Fluids - Winning Your Vet's Support


Dialysis


 

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Home > Diagnosis > Blood Chemistry Panel

 


Overview


  • The blood chemistry series of blood tests measures various parameters in the blood.

  • This page focuses on kidney parameters (BUN or urea, creatinine and SDMA), potassium and sodium, magnesium, proteins in the blood (albumin and globulin) and other readings that are often out of range in CKD cats (cholesterol, ALT, amylase, glucose and CK).


Measures of Kidney Function


 

There are a number of ways of measuring kidney function. The tests most commonly used by vets are BUN or urea, creatinine and the newer SDMA test.


Glomerular Filtration Rate (GFR)


 

The main work of the kidneys is performed by units called nephrons, which filter the blood flowing into the kidneys. The measure of the nephrons’ function is called glomerular filtration rate (GFR). There is more information about the glomerular filtration rate here.

 

GFR can be helpful for the early detection of CKD. However, it is not easy to measure GFR, so it is highly unlikely that you will ever be offered this test except occasionally at vet schools.

 

Once your cat has CKD, it is likely that knowing your cat's GFR would only be of limited use anyway. Repeated measurements of renal function in evaluating its decline in cats  (2018) Finch NC, Syme HM & Elliott J Journal of Feline Medicine and Surgery 20(12) pp1144-1148 found "The within-individual variability data suggest creatinine concentration to be the more useful marker for serial monitoring of renal function in azotaemic cats. In contrast, in non-azotaemic cats, GFR is a more useful marker for serial monitoring of renal function. The majority of cats with azotaemic CKD did not have an appreciable decline in renal function during the study."

 


Blood Urea Nitrogen (BUN) or Urea


 

This is one of the most commonly used measures of kidney function. It is known as blood urea nitrogen or BUN in the USA. In the UK and some other countries, BUN is not normally tested, instead you will see urea listed on your cat's bloodwork. 

 

During the breakdown of dietary protein in the digestive process, ammonia is absorbed in the gut. The liver then makes a substance called urea from the ammonia. The urea, in the form of urea nitrogen, is carried in the blood to the kidneys, which filter it out of the blood and excrete it via urination. Blood urea nitrogen is a measurement of the levels of nitrogen in the blood that come from urea. BUN rises in CKD because the kidneys are no longer able to excrete it efficiently.

 

Urea is not a major toxin in itself, but it is used as a marker i.e. if BUN is high, then certain toxins which cannot be easily measured will also be high. High toxin levels from kidney disease are known as uraemia. Although BUN is not a major toxin, it is important to try to control high levels because they can cause lack of appetite, nausea and vomiting.

 

Many vets who run tests in-house in the USA cannot measure BUN levels over 130, so you may see a reading of >130. If possible, it is better to know the exact level, but don't worry if this is not available. With luck, it is going to come down below 130 anyway following treatment.

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Cornell University College of Veterinary Medicine has some information about BUN.

 

Blood Urea Nitrogen (BUN) or Urea: Sudden Increase


If BUN and creatinine rise suddenly, your cat may have developed acute kidney injury or acute kidney disease on top of CKD (ACKD). There is often a particular cause, such as a kidney infection or hypertension. Kidney stones which cause blockages may also cause a sudden and high rise in both BUN and creatinine.

 

Blood Urea Nitrogen (BUN) or Urea: Other Causes of Raised Levels


BUN levels can rise for other reasons, e.g. dehydration, gastrointestinal bleeding or congestive heart failure.

 

It is also affected by both diet (since it is a by-product of the breakdown of protein) and stress. If BUN or urea levels are high yet creatinine is normal or only a little elevated, it may be because the cat is eating a high protein  diet. Effects of dietary protein content on renal parameters in normal cats (2011) Backlund B, Zoran DL, Nabity MB, Norby B & Bauer JE Journal of Feline Medicine and Surgery 13(10) pp698-704 found that BUN levels were significantly higher in healthy cats fed a high protein (46%) diet compared to a low protein (26%) diet, though (since these were healthy cats) they were still within normal range.

 

Cats with a complication of diabetes called ketoacidosis may also have elevated BUN or urea and creatinine levels, particularly if potassium and phosphorus levels are normal.

 

Therefore BUN or urea are not an entirely accurate indicator of kidney function, and you should not assume that your cat has CKD based on the BUN or urea measurement alone.

 

Blood Urea Nitrogen (BUN) or Urea: Low Levels


BUN is not normally low in CKD cats, but may be below normal in cats with liver disease or those who are suffering from starvation. One of my cats, Harpsie, once had low BUN levels when he was very sick with an infection (possibly in his liver, though I suspect it was actually a kidney infection) and had not eaten much whilst on IV at the vet's, resulting in rapid weight loss.

 


Creatinine


 

Creatinine is another waste product excreted through the kidneys. It is generally considered to be a more accurate measurement of underlying kidney function than BUN or urea because it is less affected by diet, stress and dehydration.

 

In CKD cats, both BUN/urea and creatinine will be elevated to some degree depending upon the severity of the disease; but if BUN/urea levels are high yet creatinine is only a little elevated, it usually means that the cat is dehydrated, has gastrointestinal bleeding, or is eating a high protein diet. Cats eating a raw or homemade diet tend to have higher creatinine levels.

 

Creatinine is not a linear measurement. This means that an increase in creatinine from, say, US 2 mg/dl to 3 mg/dl, indicates more loss of function than an increase from US 5 mg/dl to 6 mg/dl. Thus, whilst your cat might have a relatively high creatinine of, say US 5 mg/dl, if it increases to US 6 mg/dl, then whilst you are right to be concerned, it does not automatically indicate a massive worsening of your cat's condition. If your cat's levels jump a lot suddenly, consider the possibility of an infection (see Is There Any Hope?)

 

See the How Bad Is It? page for more information on how creatinine is used to confirm and stage CKD in cats. In all cases, two readings in a stable cat (who is not dehydrated — this can make the numbers look a lot higher than they really are), ideally after fasting (though that is not always the best choice for a CKD cat), are required before making a firm diagnosis of CKD. In practice, most vets will make the diagnosis based on bloodwork taken once during your initial visit.

 

Utility of creatinine, UPC and SDMA in the early diagnosis of CKD in dogs and cats (2019) Grauer GF International Renal Interest Society states "assessment of serum creatinine concentrations (analysed by consistent methodology), is an excellent tool to assess renal function and diagnose early CKD." See How Bad Is It? for more information.

 

Creatinine levels are one factor in the new RenalTech test, see Early Detection.

 

See below for information about low creatinine levels in end stage CKD.

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Creatinine and Muscle


Although creatinine is an accurate measure of kidney function, the cat's size is a factor. Creatinine is a by-product of muscle. Therefore small, dainty cats or kittens would be expected to have lower levels of creatinine than large, muscular cats. Effects of dietary protein content on renal parameters in normal cats (2011) Backlund B, Zoran DL, Nabity MB, Norby B & Bauer JE Journal of Feline Medicine and Surgery 13(10) pp698-704 found that the cats in this study were muscular, and that if only one creatinine reading had been taken, many of these cats would probably have been deemed to be in IRIS stage 2, even though their USG indicated that they were not in CKD.

 

Cats who lose a lot of muscle may have reduced creatinine levels, because they cannot produce as much creatinine. Overview of the urinary system (2016) Sanderson SL Merck Veterinary Manual states "Serum creatinine levels can be falsely decreased in patients with severe muscle wasting." Feeding cats with different nutritional needs: a dilemma in the multicat household (2012) Scherk M Presentation to the 73rd SCIVAC International Congress 2012 says "As an obligate carnivore, if a cat doesn’t get enough dietary protein to meet metabolic requirements, he must draw on endogenous (stored) protein sources to meet those needs. Over months cats can down regulate their protein needs and switch to use other pathways, but in the short and intermediate term, muscle will be catabolized. The resulting muscle wasting and decreased mass reduces the serum level of creatinine (Cr) measured."

 

So if your cat's creatinine level falls but your cat has lost a lot of weight and muscle, this might be the cause rather than improved kidney function.

 

Creatinine: Sudden Increase


If BUN and creatinine rise suddenly, your cat may have developed acute kidney injury or acute kidney disease on top of CKD (ACKD). There is often a particular cause, such as a kidney infection or hypertension. Kidney stones which cause blockages may also cause a sudden and high rise in both BUN and creatinine.

 

Other Reasons for Raised Creatinine


Cats with a complication of diabetes called ketoacidosis may have elevated BUN and creatinine levels, particularly if potassium and phosphorus are normal. 

 

Cats with pancreatitis also sometimes have elevated creatinine levels. If your cat has a relatively low creatinine level (around 2 mg/dl US or 175 µmol/L international) yet seems lethargic and far more ill than that mild level of kidney disease would suggest, I would consider pancreatitis.

 

Cats given medications in the ACE inhibitor family (e.g. Fortekor) or ARBs family (e.g. Semintra) may exhibit an increase in creatinine levels within a week or two of beginning the medication. This is often, but not always, temporary. See Proteinuria for more information.

 

Because creatinine is a by-product of muscle, large, muscular male cats may naturally have high normal levels of creatinine (see above).

 

An unexpected high prevalence of azotaemia in Birman cats (2002) Gunn-Moore DA, Dodkin SJ & Sparkes AH Journal of Feline Medicine and Surgery 4(3) pp165-6 says that up to 80% of Birman kittens under six months of age seem to have high levels of creatinine and BUN. As adults, this incidence reduces, but is still high, at 35%. However, these cats do not appear to develop full-blown CKD at a young age as one might expect. Monitoring them regularly would nevertheless be wise.

 

The effects of cimetidine on renal function in patients with renal failure (1980) Larsson R, Bodemar G, Kagedal B & Walan A Acta medica Scandinavica 208 (1-2) pp27-31 explains that cimetidine (Tagamet), which is sometimes used to treat gastric hyperacidity in CKD cats though it is not the best drug for that purpose, may cause an increase in creatinine. If your cat's creatinine levels rise while using Tagamet, you may find they improve once you stop the medication.

 

Reasons for Low Creatinine (Especially if BUN and Phosphorus are High)


Since creatinine is a by-product of muscle, cats who lose a lot of weight/muscle may have reduced creatinine levels, because they cannot produce as much creatinine. See above for more on this.

 

Cats with hyperthyroidism may have low creatinine levels, because they tend to lose a lot of muscle, plus hyperthyroidism masks true kidney function, making BUN and creatinine look lower than they truly are.

 

If BUN (urea) levels and phosphorus levels are high yet creatinine is normal or only a little elevated, it can mean that there is a pre-renal factor at work, for example:

 


BUN:Creatinine Ratio


 

If your cat is eating a reduced protein therapeutic kidney diet, this ratio is likely to be in the region of 10:1 or 12:1 (e.g. if creatinine is US 4, BUN is likely to be around 40-48).

 

Since BUN is affected by dietary intake, if your cat is eating a higher protein diet, this ratio will be higher, with 18:1 or 20:1 not unusual (e.g. if creatinine is US 4, BUN will be around 80-96).

 

Severe metabolic acidosis, which affects protein metabolism, may contribute to a high BUN:creatinine ratio. Dehydration also affects this ratio.

 

Gastrointestinal bleeding may also cause an increase in the BUN:creatinine ratio (since blood is a form of protein), which needs to be treated if present, since it may cause or worsen anaemia.

 


SDMA


 

This is a relatively new test available exclusively from IDEXX Laboratories which aims to detect CKD at an earlier stage than is possible when measuring creatinine or BUN levels. Comparison of serum concentrations of symmetric dimethylarginine and creatinine as kidney function biomarkers in cats with chronic kidney disease (2014) Hall JA, Yerramilli M, Obare E, Yerramilli M & Jewell DE Journal of Veterinary Internal Medicine 28 pp1676–1683 found that SDMA levels in cats who developed CKD rose above normal by a mean of 17 months before there was an increase in creatinine levels.

 

IDEXX claims that the SDMA test can therefore potentially detect CKD when up to 40% of function has been lost, whereas traditionally you could only detect CKD when 60-70% of function had been lost.

 

There is more information about the SDMA test on the Early Detection page.

 


Azotaemia


 

Azotaemia means there is increased nitrogenous waste in the bloodstream, e.g. BUN/urea and creatinine levels are elevated.

 

University of Georgia College of Veterinary Medicine explains more about it.

 

Azotaemia is divided into three categories (bear in mind that blood flows to the kidneys where it is filtered):

 

Pre-renal Azotaemia ("Before" the Kidney)


This means that the azotaemia does not involve the kidneys; rather, it is caused by a problem before the blood reaches the kidneys which reduces blood flow within the kidneys. For example:

  • infection

  • fever

  • a high protein diet

  • heart problems

  • dehydration

  • low blood pressure

Renal Dysfunction in Small Animals (2013) Brown SA Merck Veterinary Manual says "Prerenal azotemia is due to a decrease in glomerular filtration rate (GFR) from circulatory disturbances causing decreased renal perfusion (hypovolemia, cardiac disease, renal vasoconstriction)."

 

In order to distinguish between pre-renal and renal azotaemia, urine specific gravity (USG) needs to be assessed. If USG is above 1.035, then the azotaemia is likely to be pre-renal, if lower than that, it is likely to be renal. However, this may not apply if other factors are affecting urine concentrating ability, such as CKD, or if proteinuria is present.

 

If you can treat the cause of the pre-renal azotaemia promptly, there may be no permanent damage to the kidneys.

 

Interpreting the numbers: azotemia and urine specific gravity (2008) Maddison JE Presentation to the World Small Animal Veterinary Association World Congress discusses pre-renal azotaemia

 

Cornell University College of Veterinary Medicine has some information about pre-renal azotaemia.

 

Intrinsic Renal Azotaemia ("At" the Kidney)


This means the azotaemia is caused at the kidney itself, i.e. CKD or acute kidney injury.

 

Cornell University College of Veterinary Medicine has some more information.

 

Post-renal Azotaemia ("After" the Kidney)


This means the azotaemia is caused by a problem "after" the kidney, i.e. lower down the urinary tract, after the blood has already flowed into and through the kidneys.

 

A common cause is a urinary tract obstruction, such as that caused by kidney stones or struvite crystals, which stop urine from leaving the body, so toxins build up.

 

Cornell University College of Veterinary Medicine has some information about post-renal azotaemia.

 


Uraemia


 

Uraemia means that a cat has azotaemia (increased nitrogenous waste in the bloodstream), but also exhibits the associated problems commonly seen in CKD patients such as vomiting etc.

 

You may see reference to uraemic toxins: these are the toxins which the cat's damaged kidneys are unable to filter properly, so they cause many of the symptoms of CKD.

 

There is more information about uraemia here.

 

University of Georgia College of Veterinary Medicine has some information about uraemia.

 


Potassium and Sodium


 

Potassium and sodium are electrolytes (salts), which are essential to the functioning of the body. The increased urination that occurs with CKD may cause imbalances in these electrolytes.

 

Medicine Net explains more about electrolytes.

 

Potassium


Potassium is used at cellular level, in particular to help muscles function properly. If there is an imbalance, weakness, twitching and seizures may be seen.

 

Around 30% of CKD cats have low potassium levels (hypokalaemia). However, around 13% have high potassium levels (hyperkalaemia), normally cats with more advanced CKD.

 

Since potassium imbalances are so common in CKD cats, there is a dedicated page all about it. Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Cornell University College of Veterinary Medicine has an overview of potassium.

 

Sodium


Sodium is excreted by the kidneys, but levels may rise (hypernatraemia) in CKD cats because the kidneys are no longer working as efficiently and cannot adapt to changes in sodium levels as quickly. Vomiting or diarrhoea may also be factors.

 

Preparing cats for radioactive iodine treatment (2005) Shermerhorn T Presentation to the World Small Animal Veterinary Association World Congress mentions that elevated sodium levels may also be seen in cats with hyperthyroidism.

 

There is some debate as to whether elevated sodium levels can worsen hypertension (high blood pressure) in CKD cats.

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Managing sodium disorders (2013) Odunayo A Clinician's Brief Dec 2013 discusses sodium imbalances.

 

Cornell University College of Veterinary Medicine has some information on sodium.

 

Pet MD discusses high sodium levels.

 


Magnesium


 

Magnesium is a mineral found mainly in the bones and muscles which is important for many metabolic functions, such as helping to balance potassium levels in the body. It also helps regulate calcium, and since it inhibits parathyroid hormone, it has also been associated with CKD-MBD (CKD-mineral and bone disorders).

 

Prognostic importance of plasma total magnesium in a cohort of cats with azotemic chronic kidney disease (2018) Van den Broek DHN, Chang YM, Elliott J & Jepson RE Journal of Veterinary Internal Medicine 32(4) pp1359-1371 looked at magnesium levels in cats with and without CKD, and found that high phosphorus levels might be offset to a degree by normal magnesium levels.

 

The kidneys play an important role in regulating magnesium levels in the blood, so magnesium imbalances are not unknown in CKD cats, but for some reason, magnesium is only rarely measured during routine blood tests.

 

Cornell University College of Veterinary Medicine has an overview of magnesium.

 

High Magnesium (Hypermagnesaemia)


Magnesium levels may be high in CKD cats because damaged kidneys cannot excrete it properly. Prognostic importance of plasma total magnesium in a cohort of cats with azotemic chronic kidney disease (2018) van den Broek DHN, Chang YM, Elliott J & Jepson RE Journal of Veterinary Internal Medicine 27 32(4) pp1359-1371 found that only 6% of the CKD cats in the study had high magnesium levels, but that high levels were more common in Stage 4 cats. An older study of hospitalised cats, Prevalence and incidence of serum magnesium abnormalities in hospitalized cats (2002) Toll J, Erb H, Birnbaum N & Schermerhorn T Journal of Veterinary Internal Medicine 16 pp217-221, found that 50% of the cats in CKD stage 4 had high magnesium levels.

 

High magnesium levels may cause nausea, weakness and a slow heart rate.

 

Cats with high magnesium levels should not be given phosphorus binders containing magnesium. They should also not be given Normosol if they are receiving fluid therapy, because Normosol contains magnesium.

 

Pet MD has some information about high magnesium levels.

 

Low Magnesium (Hypomagnesaemia)


Some CKD cats have low magnesium levels. Prognostic importance of plasma total magnesium in a cohort of cats with azotemic chronic kidney disease (2018) van den Broek DHN, Chang YM, Elliott J & Jepson RE Journal of Veterinary Internal Medicine 32(4) pp1359-1371 found that 11.5% of the CKD cats in the study had low magnesium levels. The study states "Hypomagnesemia was associated with higher plasma FGF23 concentrations and increased risk of death." Recent advances in mineral and bone disorders in CKD Van den Broek H & Elliott J International Renal Interest Society has some information about FGF-23.

 

Usually CKD cats with low magnesium levels will also have low potassium levels. Mechanism of hypokalemia in magnesium deficiency (2007) Huang C-L & Kuo E Journal of the American Society of Nephrology 18(10) pp2649-2652 discusses the role of low potassium levels in this situation.

 

Symptoms of low magnesium levels may be similar to those seen with low potassium levels, such as weakness or twitching

 

Cats with hyperthyroidism tend to have low magnesium levels, so if your cat has both hyperthyroidism and low potassium levels, you may wish to have magnesium levels checked. Evaluation of ionized and total serum magnesium concentrations in hyperthyroid cats (2006) Gilroy CV, Horney BS, Burton SA & MacKenzie AL Canadian Journal of Veterinary Research 70(2) pp137–142 focuses on cats with hyperthyroidism but also has some useful information about magnesium levels in cats generally.

 

Low magnesium levels may also be seen in cats with metabolic acidosis, or in cats with acute pancreatitis.

 

Medscape discusses low magnesium levels.

 

Magnesium Supplementation


Hypercalcemia in chronic kidney disease (2018) Van den Broek International Renal Interest Society states "We derived a reference interval for plasma total magnesium from 120 apparently-healthy senior cats of 1.73-2.57 mg/dL or 0.71-1.06 mmol/L.".

 

If your cat has both low potassium levels and low magnesium levels, initially you should ask your vet about starting a potassium supplement. You may well find that both potassium and magnesium return to normal once the potassium supplement is begun.

 

If, however, your cat has low potassium levels which do not rise despite the use of a potassium supplement, it is possible that the low magnesium also needs to be treated. In such cases, you are unlikely to be able to raise the potassium to an acceptable level until you have also treated the low magnesium. Your vet should also consider the possibility of hyperaldosteronism if your cat has persistently low levels of magnesium and potassium, especially if hypertension is also present.

 

It can be challenging giving magnesium supplements to a CKD cat. Choosing a dose and monitoring can be difficult, and you must be very careful because elevated magnesium levels can be risky, particularly in a CKD cat whose damaged kidneys may not excrete excess magnesium efficiently.

 

Magnesium supplements made for cats do not exist to my knowledge, so you would have to use a human product. There are simple forms of magnesium, such as magnesium oxide or magnesium hydroxide, or magnesium complexes, such as magnesium citrate (the citrate apparently helps increase absorption) or magnesium malate. Many human supplements containing magnesium oxide seem to contain 250mg per tablet, far too much for a cat.

 

Newman Veterinary explains more about low magnesium levels, and suggests a dosage of 1-2 mEq/kg daily, with a check one week after starting the supplement.

 

Plumb's Veterinary Drug Handbook also suggests a dose of 1-2 mEq/kg per day if using oxide or hydroxide salts.

 

One person I knew of gave her cat an eighth of a 250mg magnesium oxide supplement each day, i.e. around 30mg per day.

 

A member of Tanya's CKD Support Group gave her 4 kg cat 1.8ml of milk of magnesia, as recommended by her vet. This contained around 60mg of magnesium, so twice the dose of the person in the preceding paragraph.

 

Another member gave her cat 15 mg of magnesium citrate twice a day.

 

The safest thing is to let your vet determine the dose.

 

Monitor your cat carefully (possible side effects include diarrhoea, more serious problems include heart arrhythmias). Never give magnesium supplements without your vet's knowledge and approval.


Total Protein (Proteins in the Blood)


 

Total protein is the sum of the two proteins in the blood, albumin and globulin.

 

High total protein levels may be seen when a cat is dehydrated. In this case, albumin will probably also be high.

 

High levels of total protein may also be seen in cases of infection or inflammation.

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Cornell University College of Veterinary Medicine has some information on total protein.

 


Albumin (Alb)


 

This is the main protein in blood. Albumin may be high or low. Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Cornell University College of Veterinary Medicine has some information on albumin.

 

Albumin: High


If albumin is high, it may indicate dehydration. In this case, total protein will probably also be high.

 

Albumin: Low


Albumin may be low in a cat with gastrointestinal bleeding or some other kind of problem which causes inadequate nutrition. Prolonging life and kidney function (2009) Chew DJ & DiBartola SP CVC in Kansas City Proceedings states "Maintenance of stable body weight and serum albumin concentration suggests adequate intake of calories and protein whereas progressive declines in body weight and serum albumin concentration suggest malnutrition or progression of disease and are indications to increase the amount of protein fed."

 

Cats with a chronic infection or chronic inflammation, such as Inflammatory Bowel Disease (IBD), may have low albumin and total protein levels, as may cats with liver disease.

 

Nephrotic syndrome will often cause low albumin levels, but this syndrome is quite rare in cats.

 

Hypoalbuminemia (2019) Allen J Clinician's Brief Apr 19 p21 lists the possible causes of low albumin levels.

 

One of albumin's roles is to provide pressure to keep water in the blood, so if it falls too low, there is a greater risk of fluid build up (oedema or ascites). This can sometimes happen if your cat is being overhydrated.

 

If your cat's albumin level is very low (below 2 mg/dl US, 20 mmol/l international), please discuss this with your vet, because it can be quite dangerous.

 

If albumin is low, usually calcium will also be low. 

 


Globulins


 

Globulins are calculated from the values for albumin and total proteins i.e.

globulins = total protein minus albumin

Globulins contain antibodies (immunoglobulins), so high levels may be seen when infection or inflammation is present. Very high globulin levels combined with a low albumin:globulin ratio may be a sign of FIP (feline infectious peritonitis).

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Hyperglobulinemia (2020) Allen J Clinician's Brief May 20 p10 lists the possible causes of elevated globulin levels.

 

Cornell University College of Veterinary Medicine has information on globulins.

 


Albumin:Globulin Ratio (AG Ratio)


 

This is as it suggests, the ratio between albumin and globulin. It is usually around 1:1. If the ratio is lower than 1:1, then normally globulins are high. If the ratio is higher than this, then normally albumin levels are high.

 

The AG ratio needs to be looked at in conjunction with the total protein level:

  • A normal AG ratio with a high total protein level indicates that there is probably dehydration.

  • A low albumin:globulin ratio combined with very high globulin levels may be a sign of FIP (feline infectious peritonitis). An AG ratio below 0.4 combined with elevated globulins, indicates that FIP is quite likely, assuming other causes of a low AG have been ruled out, whereas an AG ratio over 0.8 rules out FIP.

Cornell University College of Veterinary Medicine has some information on the albumin:globulin ratio.

 


Other Test Results Which May Be Out of Range



Creatine Kinase (CK) and Creatine Phosphokinase (CPK)


 

These are two slightly different names for the same muscle enzyme, which is released when muscle is damaged. In one study, 60% of sick cats had elevated CK levels, so do not panic if your CKD cat's CK level is elevated.

 

In most CKD cats, there is usually only a mild increase if any, and this might simply be because of the stress of being held and having blood taken at the vet’s; occasionally, levels also increase after prolonged inactivity or if a cat has a seizure. 

 

In Zen and the art of cat maintenance I and II (2004) Wolf A Practical Stuff From ACVIM mentions that "Most increases in CPK are due to anorexia in cats", but Diagnostic and prognostic value of serum creatine-kinase activity in ill cats: a retrospective study of 601 cases (2010) Aroch I, Keidar I, Himelstein A, Schechter M, Shamir MH & Segev G Journal of Feline Medicine & Surgery 12(6) pp466-75 found that cats with elevated CK levels were actually less likely to be anorexic. This study concluded that "Increased CK activity is very common in ill cats."

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table. Many labs have a maximum level of 300, and a level of up to 500 is not usually cause for concern. If levels are high, it may indicate some kind of muscle disease; alternatively, very high levels of CK are often seen when an animal has heart issues. If your cat's level is over 1800, your vet should investigate further.

 

Cornell University College of Veterinary Medicine has some information about CK levels.

 


Cholesterol (Chol)


 

High cholesterol levels do not have the same significance for cats that they do for humans, but are usually secondary to some other disease. As in humans, bloodwork results will vary depending upon whether the blood is taken after fasting. It is not uncommon for CKD cats to have increased cholesterol levels.

 

Occasionally, high cholesterol levels are seen in cats with nephrotic syndrome, but this syndrome is quite rare in cats.

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Cornell University College of Veterinary Medicine has some information about cholesterol levels.

 

Pet MD discusses cholesterol levels in cats.

 


Glucose (Glu)


 

Glucose is also known as blood sugar. This value may increase suddenly because of stress — it is not uncommon for this value to be high in cats who get stressed or frightened at the vet’s. Therefore a high level on one occasion should not be taken to indicate diabetes, urine testing is also required.

 

Overview of feline bloodwork (2008) Jensen A Zimmer Feline Foundation states "Glucose also has a tendency to show dramatic increases in a healthy cat under acute stress.  Normal blood glucose should be well below 150 mg/dl.  In most species, a glucose measurement of over 200 would strongly suggest diabetes.  In the feline, however, stress alone can cause glucose to spike as high as 250 mg/dl.  A value over 300 is unlikely to be due to stress alone. One way to differentiate between a glucose spike due to acute stress and high blood glucose due to diabetes is through urinalysis.  If there is no glucose in the urine in the face of high blood glucose, it may be due to the fact that the blood glucose has not been high long enough to overflow into the urine, suggesting an acute spike.  This is not definitive, however.  Presence of glucose in the urine is, however, highly suggestive of diabetes."

 

Glucose levels may be elevated in cats with hyperthyroidism or secondary hyperparathyroidism.

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Cornell University College of Veterinary Medicine has some information on glucose and mentions that stress may make glucose levels rise (hyperglycaemia) in cats.

 


ALT (Alanine Aminotransferase) or SGPT (serum glutamic-pyruvic transferase)


 

This is an enzyme which is largely found in muscle, the liver and the brain. It often leaks out of damaged liver cells, so it may be an indicator of liver disease, although it is sometimes elevated in hyperthyroidism. Cats on methimazole for hyperthyroidism may also have elevated ALT or SGPT enzymes and low white blood cells.

 

If a sample is haemolysed, ALT may be elevated.

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table. Mild elevations are not normally cause for concern — one of my cats has mildly elevated ALT for years without problems.

 

Cornell University College of Veterinary Medicine has some information about ALT.

 


Amylase (Amyl)


 

Amylase is a digestive enzyme made in the pancreas that breaks carbohydrates down into simple sugars.

 

Because amylase is made by the pancreas, many vets seem to assume that an increase in this enzyme must indicate pancreatitis. Whilst this is often true for other species, it does not usually apply to cats, particularly CKD cats, because amylase is excreted by the kidneys, so it is by no means uncommon for it to be elevated in CKD.

 

This is not usually a cause for concern — a value up to 2200 is not uncommon in CKD cats. However, if the level is much higher, around three times normal level, and your cat is showing other symptoms of pancreatitis combined with relatively low CKD values that seem to be out of line with how ill your cat is acting, then you might want to rule it out.

 

Approximate normal levels (precise ranges vary from laboratory to laboratory) for cats are in this table.

 

Cornell University College of Veterinary Medicine has some information about amylase.

 

 

 

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This page last updated: 13 Nov 2020

 

Links on this page last checked: 30 June 2020

 

 

   

 

*****

 

TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE EXTREMELY DANGEROUS.

 

I have tried very hard to ensure that the information provided in this website is accurate, but I am NOT a vet, just an ordinary person who has lived through CKD with three cats. This website is for educational purposes only, and is not intended to be used to diagnose or treat any cat. Before trying any of the treatments described herein, you MUST consult a qualified veterinarian and obtain professional advice on the correct regimen for your cat and his or her particular requirements; and you should only use any treatments described here with the full knowledge and approval of your vet. No responsibility can be accepted.

 

If your cat appears to be in pain or distress, do not waste time on the internet, contact your vet immediately.

 

*****

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