Factors Which May Affect Test Results

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Normal Ranges for Tests

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Home > Diagnosis > Test Ranges, and Factors Which May Affect Results



  • There are a number of factors which may affect test results. This page discusses the pros and cons of these factors, such as whether it is necessary to fast a cat before blood tests.

  • This page gives a rough idea of normal ranges for tests commonly run on CKD cats, and explains why there are differences between various laboratories. It also has veterinary links explaining more about test results.

  • Ranges for test results differ between the USA and the rest of the world. This page explains those differences.

Factors that May Affect Test Results                                                               Back to Page Index


Certain factors may affect test results, and in certain cases may make the results somewhat inaccurate. Stress, fasting before a test, or how the test is handled by the laboratory may all have an effect. This section covers some of the more commonly seen issues.


Cornell University College of Veterinary Medicine has more information on these factors. Click on the links on the left for more information.

Fasting a Cat Before Tests

If cats are not fasted before blood draws, then lipaemia may occur, particularly if the cat has eaten a meal rich in fat. This means that lipids (fats) are suspended in the blood, which may make the sample thicker and harder to test.


However, lipaemia is relatively rare in feline blood samples, and even if it is present, it is unlikely to make a major difference to the test results. Therefore it is not usually necessary for a cat to fast before the usual tests for CKD, and overall I think it is a bad idea because an empty stomach can increase the risk of stomach acid; plus when they are being fasted, cats simply do not understand why we won't feed them, which is stressful for them, especially if other family cats continue to get fed whilst they do not. However, for certain specialised tests, such as those for parathyroid hormone or pancreatitis, fasting for twelve hours may be necessary; be guided by your vet.


Cornell University College of Veterinary Medicine has more information on lipaemia.


Stopping Fluids Before Testing

I have heard of some vets asking that people not give their cats fluids for a day or two (in one case, a week!) before bloodwork. I do not understand this: since the cat normally receives fluids, surely you will obtain more accurate results, reflecting how the cat's bloodwork normally looks, if the cat has his/her usual levels of hydration. But I do recommend that you try to be consistent i.e. always have the tests done before sub-Qs or after sub-Qs, at the same time of day if possible.


Stressed Cats or Cats Who Fight Blood Draws

If your cat fights at the vet, or gets very stressed, this may have an effect on some of the test results. For example, blood glucose levels are often raised in stressed cats, so they do not automatically indicate that diabetes is present. Similarly, CK or CPK, a muscle enzyme, may be raised because of a bad blood draw.



Occasionally bloodtest results will mention that they are haemolysed. This means the blood cells being tested have ruptured, often as a result of poor handling. Mild haemolysis should not have any real effect, but a grossly haemolysed sample may affect results, causing some values (such as phosphorus) to appear higher than they are and others (such as creatinine) to appear lower. Potassium will usually appear higher than it really is, but occasionally it will appear lower. If a sample has been haemolysed, you might wish to ask your vet to take new blood samples and run the tests again.


Cornell University College of Veterinary Medicine has information on the impact of haemolysis.

BD Tech Talk has more information on haemolysed samples.


Clumping Platelets

Platelets are the component of blood which causes it to clot. If they were not present, we would bleed to death whenever we got cut.


Unfortunately when a sample of blood is taken, some of the platelets may "clump" (stick together), especially if the blood sample is not mixed with the anticoagulant immediately. Clumping platelets are extremely common in cats  - they occur in as many as 75% of cat blood draws. They are even more likely if it is difficult to get blood from the cat. Taking them from a leg rather than from the neck may also be a factor.


The clumping means that it can be difficult to count the platelets accurately, which in turn means that the number may appear low. However, you may sometimes see platelet counts listed as low, followed by a comment that the platelet estimate is "adequate." This means that the person running the test could not tell the platelets apart enough to be able to count them, but could see that overall there are enough.


If a cat truly has low platelets, then you may see increased bleeding e.g. from the nose, gums or in urine.


Cornell University College of Veterinary Medicine has more information on platelets.

Pet Place has some information about low platelets (no need to register to read the article, just click on Close at the bottom of the irritating pop-up).


Differences Between US and International Measurement Systems         Back to Page Index


The USA uses a different measurement system to the rest of the world, which uses the SI system (SystŔme Internationale). Although I am familiar with both systems, having lived in both the UK and the USA, Tanya's Feline CRF Support Group has primarily American members, so you will get more feedback when you join if you post your results in American values.


In order to do this, there is a handy converter on the Veterinary Information Network website. Remember to choose the feline measurements and to enter the SI (international) measurements for conversion to US equivalents, not the other way round. When converting urea from your international results, choose Urea Nitrogen from the dropdown menu - that is the nearest US equivalent. When converting creatinine, be sure to choose creatinine rather than creatine, which is also in the dropdown menu.


You can also use the Jay Clinical Services website, but you need to know a bit more about which values to choose. Most international values are in mmol/L and if you are trying to convert to US values, you will be converting to mg/dl. Creatinine is slightly different and the international value is in Ámol.


Sometimes the conversion site is down, but usually not for long. However, if you can't get it to work, here is a rough guide to the calculations:


Urea (BUN)

If you have a urea measurement in mmol/L, you multiply the international value by 2.8:

  • e.g. urea of 50 is a BUN of 140.

If you don't have a calculator, you can do it roughly by simply multiplying by 3:

  • e.g. urea of 50 is about BUN 150. Note this slightly overstates it.

If you have a urea measurement in mg/dl (often the case in Germany, Austria and Italy), you multiply the international value by 2.14:

  • e.g. urea of 65 is a BUN of 140.

If you don't have a calculator, you can do it roughly by simply multiplying by 2:

  • e.g. urea of 65 is about BUN 130. Note this slightly understates it.


You divide the international value by 88.36:

  • e.g if a cat has creatinine of 300, then it is 3.4 in US values.

If you don't have a calculator, you can just do it roughly by dividing by 100 and adding on about 10%:

  • e.g. if a cat has a creatinine of 300, dividing by 100 gives you 3, then add on 10%, which gives you 3.3. Note  this slightly understates it.


You multiply the international value by 3.1:

  • e.g. phosphorus of 4 international is 12.4 in US values.

If you don't have a calculator, you can do it roughly by simply multiplying by 3:

  • e.g. phosphorus of 4 is about 12 in US values. Note this slightly understates it.


This is the same in both systems, so no need to convert anything.



This is the same in both systems. However, sometimes in international values, it will be shown differently,e.g. 0.30% rather than 30%. If this happens, simply move the decimal place along two places.


Normal Ranges for Cats                                                                                      Back to Page Index

Why Ranges Differ Between Laboratories

Cornell University College of Veterinary Medicine provides some information on why reference ranges differ from laboratory to laboratory.

Lab Tests Online also explains more about this.


Normal Ranges for Blood and Urine Tests

These ranges are approximate - if those your vet provides are different, which is quite likely, you should be guided by them. These ranges are also not directly comparable; for example, the upper limit for urea/BUN is noticeably lower in the SI system.


This table contains ranges, but that does not necessarily mean that a result within these ranges is acceptable. For example, a CKD cat should aim for a phosphorus level no higher than 4 (US) or 1.3 (international), while most CKD cats do better if their potassium level is around 4.4.



Normal Range (International) Normal Range (USA)
Urea (BUN) 3.5 - 8.0 mmol/L

9.8 - 35.0 mg/dl

Creatinine 40 - 180 Ámol/L

0.5 - 1.80 mg/dl

BUN:creatinine ratio 4 - 35

4 - 35

Potassium 3.5 - 5.5  mmol/L

3.5 - 5.5 mEq/l

Phosphorus 0.81 - 1.61  mmol/L

2.5 - 7.50 mg/dl

Calcium 2.0 - 2.8  mmol/L

 8.0 - 11.2 mg/dl

Phosphorus x Calcium less than 5

less than 70

Sodium 141 - 155  mmol/L

141 - 155 mEq/l

TCO2 17 - 23 mmol/L

17 - 23 mEq/l

Anion Gap 10 - 27

10 - 27

Packed Cell Volume 29 - 45%

29 - 45 %

RBC 5.5 - 9.9 

5.5 - 9.9

Reticulocytes 0.1 - 1.0

0.1 - 1.0

White Blood Cells 5000 - 18000

6 - 19

Neutrophils (segs)

2500 - 12000

60 - 80

Neutrophils (bands) 100 - 300

0 - 3

Eosinophils 0 - 1500

0 - 5

Lymphocytes 1500 - 7000

17 - 32

Monocytes 0 - 850

0 -5

CK/CPK 88 - 300

88 - 300 U/L

Cholesterol 1.9 - 4.2 mmol/L 

65 - 200 mg/dl

Glucose 3.85 - 8.25 mmol/L

70- 150 mg/dl

Amylase 100-1500 /Ál

100-1500 U/L

ALT 10-130 /Ál

10-130 U/L

Albumin 25 - 40 g/L

2.5 - 4.0 g/dL

Globulin 23 - 53 g/L

2.3 - 5.3 g/dL

Total protein 5.5 - 8.1 g/dl

5.5 - 8.1 g/dL

Blood pressure Max: 145 (systolic)

Max: 145 (systolic)

USG 1.008 - 1.060

1.008 - 1.060

Osmolality 270 - 320


Temperature 38-39 C

101 - 102.5 F


Normal Temperature


Temperature 38-39 C

101 - 102.5 F


Pet Place explains how to take your cat's temperature (no need to register to read the articles, just click on Close at the bottom of the irritating pop-up).


Normal Heart and Respiration Rates

Surprisingly, there appears to be little agreement on what is normal in terms of pulse and respiration, as the following table shows.


Some people whose cats have heart problems learn how to use a pediatric stethoscope on their cats. Even if you don't do this (I never have), ask your vet for guidance on what is normal for your cat. If your cat appears to be having trouble breathing, particularly if s/he breathes with the mouth open, it is a medical emergency and you should seek veterinary help immediately.


Respirations are normally measured when the cat is asleep. They will always be more frequent when the cat is awake. Breathing in and out once counts as one breath.



Pulse (beats per minute)

Respirations per minute

Merck Veterinary Manual 120 - 140  
Veterinary Drug Handbook 100 - 120 (old cats)  
The Cornell Book of Cats 160 - 240 20 - 30
The Pill Book Guide to Medication for Your Dog and Cat 160 - 180 20 - 40
Pet Place 160 - 220 20 - 30
University of Michigan 130 - 160 20 - 30
Colorado State University* 160 - 220 20 - 30

*This site also gives instructions on how to take the measurements


Veterinary Links Explaining Blood Tests                                                       Back to Page Index

To obtain more information on what the different measurements on your cat's bloodwork mean, try some of these websites:


Cornell University College of Veterinary Medicine ľ excellent detailed information on blood work, and urinalysis.

Washington State University - helpful information, and perhaps easier to understand than Cornell.

Animal Hospital of Rowlett discusses the tests usually contained in a geriatric panel.

Pet Education has some helpful sections:

Pet Place also has helpful information (no need to register to read the articles, just click on Close at the bottom of the irritating pop-up):

NationWide Laboratories is a UK website which gives a brief description of what the various items in bloodwork mean, together with approximate UK (international) ranges.

Small Animal Clinical Diagnosis by Laboratory Methods (2003) Willard MD & Tvedten H is a book which explains laboratory tests.  



Back to Page Index

This page last updated: 02 December 2013

Links on this page last checked: 04 April 2012