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BLOOD SUGAR · CATS

Blood sugar in cats: normal glucose levels and why stress can raise them

A high glucose is one of the most common surprises on a cat’s blood work. Often it is the stress of the visit, sometimes it is diabetes. Here is how to read the GLU line, why cats are so prone to stress hyperglycemia and which test helps tell the two apart.

Written by the AI DiagAnimals editorial teamReviewed by the AI DiagAnimals TeamUpdated Our editorial policy

The essentials

Normal blood glucose in cats is roughly 60–120 mg/dL (3.3–6.7 mmol/L), depending on the laboratory. Cats produce a marked “stress” hyperglycemia: in healthy cats, a short stressor raised glucose from about 83 to 162 mg/dL on average. A single high value therefore does not mean diabetes. Fructosamine, which reflects the previous 2–3 weeks, helps tell stress from persistent high sugar.

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Normal blood sugar for cats

Glucose (GLU) is the sugar the body uses for energy. Its level is kept within a narrow range by insulin and other hormones. The Merck Veterinary Manual lists 60–120 mg/dL (3.3–6.7 mmol/L) for cats [1]; each laboratory has its own interval.

Glucose falls in a blood sample that waits before the serum is separated from the cells, because the cells keep consuming it. A falsely low glucose in a cat with no signs is often this sample artefact [2].

How to read the glucose line

Here is an example line, followed by a converter for reports in other units.

An annotated line from a lab report · Illustrative example
AbbreviationResultUnitLaboratory intervalFlag
GLU Glucose214mg/dL60–120H
  1. Abbreviation GLU or glucose. Some reports also show fructosamine further down.
  2. Result 214 mg/dL in this illustrative line: high, but within the range that stress alone can produce in a cat [2, 3].
  3. Unit mg/dL in the United States, mmol/L in Europe and g/L on some French reports: 214 mg/dL ≈ 11.9 mmol/L.
  4. Laboratory interval The example uses the cat interval of the Merck Veterinary Manual [1].
  5. Flag H: above the interval. In a cat, the next question is: stress, or persistent hyperglycemia?

Unit converter

Equivalent values

  • Glucose, mmol/L–
  • Glucose, g/L–

Conversion only changes the unit. Compare the result with the interval printed by the laboratory that measured it.

Stress hyperglycemia: why cats are different

Cats produce marked stress hyperglycemias [2]. In a study of 20 healthy cats given a 5-minute spray bath, glucose rose in all of them, from a baseline of 83 mg/dL to a mean peak of 162 mg/dL; it returned to normal within 90 minutes in 12 of the 20 cats. Struggling was the strongest predictor [3].

If glucose exceeds the kidney threshold, about 280–290 mg/dL in cats, sugar can also appear in the urine. Stress can cause this too, but it should be transient; persistent glucose in the urine is more compatible with diabetes [2].

Gentle, cat-friendly handling during sampling reduces stress hyperglycemia [3].

Fructosamine: telling stress from diabetes

Fructosamine is formed when glucose binds to blood proteins. Because those proteins last about 2–3 weeks, fructosamine reflects the average glucose over that period rather than the moment of sampling [4].

In healthy cats, 90 minutes of high blood sugar did not raise fructosamine, which makes it useful to separate a short stress response from persistent hyperglycemia, especially when glucose is moderately high and only one sample is available [5]. The 2018 AAHA guidelines stress the importance of avoiding unnecessary insulin in cats with transient hyperglycemia [6].

Low blood sugar in cats

  • Sample artefact: the most common cause of a low result, when the sample waited before processing [2].
  • Insulin: too much insulin in a diabetic cat; avoiding hypoglycemia is a core goal of diabetes management [6].
  • Illness: severe infection (sepsis), liver failure or not eating can lower glucose [2].

Signs of a truly low blood sugar include weakness, wobbling, trembling, confusion and seizures [2]. In a diabetic cat on insulin, these signs are an emergency.

Results often read with glucose

Fructosamine

The 2–3 week average that tells stress from persistent high sugar [4, 5].

Urinalysis

Glucose and ketones in the urine, read with the urine concentration.

Read the article

Cat blood work overview

The other cat-specific stress effects: white cells and lymphocytes.

Read the article

For dogs, see blood sugar in dogs. En français : la glycémie du chat et du chien.

Questions to ask your veterinarian

  1. Could stress during the visit explain this glucose result?
  2. Should we measure fructosamine or check the urine for glucose?
  3. Was the sample processed quickly enough for the glucose to be reliable?
  4. If diabetes is suspected, which tests confirm it?
  5. If my cat is on insulin, what should I do if I see signs of low sugar?
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Frequently asked questions

What are normal glucose levels for cats?

Roughly 60–120 mg/dL (3.3–6.7 mmol/L) in the Merck Veterinary Manual table; each laboratory sets its own interval [1].

My cat has a blood sugar of 300. Is this normal?

It is above the interval. It can come from stress in a cat that struggled during sampling, or from diabetes. Your vet may measure fructosamine or check the urine to tell them apart [2, 5].

How does a cat act when blood sugar is high?

A brief stress-related rise causes no signs. Persistent high sugar, as in diabetes, typically causes increased thirst and urination, increased appetite with weight loss, and sometimes weakness of the back legs.

Can I check my cat’s blood sugar at home?

Yes, many owners of diabetic cats do, under their vet’s guidance; the AAHA guidelines describe home monitoring as ideal but not mandatory [6].

What is a fructosamine test for cats?

A blood test reflecting the average glucose over about 2–3 weeks. It is not raised by a short stress response, which makes it useful when a single glucose is high [4, 5].

Sources

  1. Merck Veterinary Manual. Serum biochemical analysis reference ranges. merckvetmanual.com/reference-values-and-conversion-tables/reference-guides/serum-biochemical-analysis-reference-ranges
  2. eClinPath, Cornell University College of Veterinary Medicine. Glucose. eclinpath.com/chemistry/energy-metabolism/glucose
  3. Rand JS et al. Acute stress hyperglycemia in cats is associated with struggling and increased concentrations of lactate and norepinephrine. J Vet Intern Med. 2002;16(2):123-132. pubmed.ncbi.nlm.nih.gov/11899027
  4. eClinPath, Cornell University College of Veterinary Medicine. Fructosamine. eclinpath.com/chemistry/energy-metabolism/fructosamine
  5. Lutz TA, Rand JS, Ryan E. Fructosamine concentrations in hyperglycemic cats. Can Vet J. 1995;36(3):155-159. pubmed.ncbi.nlm.nih.gov/7757920
  6. Behrend E et al. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2018;54(1):1-21. doi.org/10.5326/JAAHA-MS-6822

Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.

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