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Blood sugar in dogs: normal glucose levels, high and low results explained

Glucose is on almost every chemistry panel. A slightly high value is common and often harmless; a low value can be an emergency or just a sample problem. Here is how to read the GLU line, what can move it and when to act fast.

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

The essentials

Normal blood glucose in dogs is roughly 76–119 mg/dL (4.2–6.6 mmol/L), depending on the laboratory. A mildly high value can follow a meal or stress; a persistently high one, with sugar in the urine, suggests diabetes. A low value (hypoglycemia) is most often a sample artefact, but true hypoglycemia, from insulin, infection, Addison’s disease or a tumour, can cause weakness and seizures.

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Normal blood sugar for dogs

Glucose (GLU) is the body’s main fuel, and the brain depends on it almost entirely [1]. The Merck Veterinary Manual lists 76–119 mg/dL (4.2–6.6 mmol/L) for dogs [2]; each laboratory sets its own interval.

A meal changes glucose less than people expect. In a study of 100 healthy dogs, glucose moved beyond the test’s allowable error after feeding in only 17 dogs [3], and only 6 went above the reference interval [1].

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 Glucose58mg/dL76–119L
  1. Abbreviation GLU or glucose.
  2. Result 58 mg/dL in this illustrative line. If the dog is bright and well, the first suspect is the sample [1].
  3. Unit mg/dL in the United States, mmol/L in Europe and g/L on some French reports: 58 mg/dL ≈ 3.2 mmol/L.
  4. Laboratory interval The example uses the dog interval of the Merck Veterinary Manual [2].
  5. Flag L: below the interval. Your vet checks how the sample was handled and whether the dog shows signs.

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.

Low blood sugar (hypoglycemia) in dogs

The most common cause of a low glucose result is an artefact: when serum is not separated from the blood cells quickly, the cells keep consuming sugar in the tube. A very low value in a dog without signs should raise this suspicion [1].

  • Insulin: an overdose or a missed meal in a diabetic dog on insulin [1, 4].
  • Severe infection (sepsis) and, in dogs, Addison’s disease and insulinoma, a tumour that secretes insulin, are common true causes [1]. Addison’s disease is checked with an ACTH stimulation test.
  • Toy and small-breed puppies: juvenile hypoglycemia linked to small glycogen reserves [1].
  • Severe liver disease or portosystemic shunts, although low glucose appears only once more than 70% of liver function is lost [1].

Signs of true hypoglycemia include lethargy, poor coordination, weakness, trembling, blindness, seizures and, in severe cases, coma [1].

High blood sugar in dogs

  • After a meal or with stress: usually mild and short-lived in dogs [1, 3].
  • Medicines: some sedatives and high doses of corticosteroids can raise glucose [1].
  • Diabetes mellitus: a persistent high glucose. Above about 180–200 mg/dL, the dog’s kidney threshold, sugar spills into the urine [1].
  • Hormonal conditions such as an excess of cortisol can cause insulin resistance [1].

Fructosamine, which reflects the average glucose over the previous 2–3 weeks, helps confirm persistent hyperglycemia and monitor diabetic dogs [5]. The 2018 AAHA guidelines cover diagnosis and monitoring, including home glucose checks [4].

Results often read with glucose

Urinalysis

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

Read the article

ALP and cholesterol

Often raised alongside glucose when cortisol is in excess.

Read the article

ACTH stimulation test

Checks for Addison’s disease, one cause of low blood sugar in dogs.

Read the article

For cats, whose stress response is very different, see blood sugar in cats.

En français : glycémie et hypoglycémie du chien.

Questions to ask your veterinarian

  1. Was the sample processed quickly enough for the glucose to be reliable?
  2. Should we repeat glucose, or measure fructosamine?
  3. Do my dog’s signs fit with a true low or high blood sugar?
  4. Does the urinalysis show glucose or ketones?
  5. If my dog is on insulin, what should I do at home if I see signs of low sugar?
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Frequently asked questions

What is a normal blood sugar level for dogs?

Roughly 76–119 mg/dL (4.2–6.6 mmol/L) in the Merck Veterinary Manual table; your laboratory’s interval applies [2].

What is hypoglycemia in dogs?

A blood glucose below the normal range. The brain depends on glucose, so a true hypoglycemia can cause weakness, trembling and seizures. A low result in a well dog is often a sample artefact [1].

How to treat low blood sugar in dogs at home?

If your dog is diabetic, follow the emergency plan your vet gave you, then call your vet or an emergency clinic straight away. Never give food or anything by mouth to a dog that is having a seizure or cannot swallow.

Does food affect blood sugar tests in dogs?

Less than expected: in a study of 100 healthy dogs, a meal changed glucose meaningfully in only 17 [3]. Follow your vet’s fasting instructions anyway, as other tests can be affected.

What blood sugar level indicates diabetes in a dog?

There is no single cut-off on one test. Persistent hyperglycemia with sugar in the urine, confirmed by repeat glucose or fructosamine, supports diabetes [1, 4, 5].

Sources

  1. eClinPath, Cornell University College of Veterinary Medicine. Glucose. eclinpath.com/chemistry/energy-metabolism/glucose
  2. Merck Veterinary Manual. Serum biochemical analysis reference ranges. merckvetmanual.com/reference-values-and-conversion-tables/reference-guides/serum-biochemical-analysis-reference-ranges
  3. Yi KC et al. Effect of withholding food versus feeding on creatinine, symmetric dimethylarginine, cholesterol, triglycerides, and other biochemical analytes in 100 healthy dogs. J Vet Intern Med. 2023;37(2):626-634. doi.org/10.1111/jvim.16630
  4. 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
  5. eClinPath, Cornell University College of Veterinary Medicine. Fructosamine. eclinpath.com/chemistry/energy-metabolism/fructosamine

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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