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Signs of Diabetes in Dogs

By the Dog Health Handbook team · Updated · Fact-checked against current veterinary references (see sources)

Key takeaways

  • First signs: drinking and urinating more, hunger and weight loss.
  • Cataracts develop in about half of diabetic dogs within about 6 months.
  • Vomiting, weakness or not eating can mean DKA, an emergency.
  • Stress, Cushing's and kidney disease can look similar.
  • Vets diagnose diabetes with blood and urine glucose tests.

Table of Contents

Research Early signs Cataracts Infections Emergency signs Look-alikes Diagnosis FAQ Sources

Diabetes and Blood Sugar Quicklinks

Diabetes Causes Signs Treatment Diet Ketoacidosis (DKA) Low Blood Sugar Life Expectancy Diabetes Insipidus

The first signs of diabetes in dogs are drinking much more water, urinating more (sometimes with accidents), a bigger appetite and weight loss despite eating well.1,2,3 These happen because once blood sugar rises above what the kidneys can hold back, sugar spills into the urine and pulls water with it.1 Other signs include cloudy eyes from cataracts, which developed in about half of diabetic dogs within about 6 months in an older study, and repeated bladder or skin infections.4,5,6 Signs usually come on gradually over weeks to months, and a dog can look fairly normal early on.6,1 If a diabetic dog stops eating, vomits or becomes weak, ketoacidosis may be developing, and that's an emergency.1,7 Vets confirm diabetes with blood and urine tests showing high blood glucose plus glucose in the urine.1

Go to a vet right away if your dog has:

  • Heavy drinking and urination with vomiting, not eating, weakness or fast breathing1,8
  • A sweet or chemical smell on the breath1,9
  • Sudden cloudiness in one or both eyes, or a red, painful eye10

What the Research and Guidelines Say

  • Clear diagnostic rule. The 2026 AAHA guidelines define diabetes as "a fasted or nonfasted BG ≥200 mg/dL and evidence of glucosuria."1
  • Cataracts come early. In UK primary care, 32.8% of diabetic dogs already had cataracts or developed them within 3 months of diagnosis.11
  • Heat-cycle diabetes. In unspayed females, signs often appear 30 to 50 days after a heat cycle.1
  • Look-alikes. In Fanconi syndrome, a kidney disease, "the combination of urine glucose and normal or low blood glucose" points away from diabetes.12

Early Signs

  • Drinking more (polydipsia) and urinating more (polyuria), including accidents in the house1,7
  • A bigger appetite (polyphagia) with weight loss1,2
  • A dull coat and muscle loss1
  • Tiredness or weakness6

Cataracts and Vision Loss

"Cataracts are a common side effect of canine diabetes."5 In an older study of 200 diabetic dogs, about half developed cataracts within about 6 months of diagnosis, and 75 to 80% within about a year to 16 months.4,10 A complete cataract and vision loss "can develop within days."10 Swelling lenses can also cause painful eye inflammation (uveitis), so diabetic dogs need regular eye checks.10 See cataracts in dogs.

Infections

Diabetic dogs are prone to bladder, prostate and skin infections.6 Infections also make diabetes harder to control.13 Your vet may culture the urine if there are signs of infection.1

Signs of a Diabetic Emergency

When ketones build up, dogs become lethargic and weak, stop eating, vomit and seem depressed. AAHA notes that "if ketosis is present, the pet's breath may have a sweet odor."1 This is diabetic ketoacidosis. See DKA in dogs.14

What Can Be Mistaken for Diabetes?

  • Stress: a vet visit can mildly raise blood sugar for 4 to 6 hours.1
  • Other hormone diseases: Cushing's disease and, rarely, acromegaly1
  • Acute pancreatitis, severe infection (sepsis) and some medicines1
  • Fanconi syndrome: glucose in the urine with normal blood sugar, inherited in Basenjis12
  • Other causes of heavy drinking: kidney disease, Cushing's disease, pyometra and diabetes insipidus. See diabetes insipidus.15,16

How Vets Diagnose Diabetes

  • Blood glucose of 200 mg/dL or higher, plus glucose in the urine1
  • Fructosamine, a blood test that reflects average blood sugar over the previous 7 to 10 days17
  • Baseline tests: blood count, chemistry panel, urinalysis and often a urine culture. Urine ketones are checked too.1

Home urine strips give only a rough idea and can't diagnose diabetes.17,5

Frequently Asked Questions

What are the first signs of diabetes in a dog?

Drinking and urinating more, a bigger appetite and weight loss.

How does a dog act when blood sugar is high?

Thirsty, urinating a lot, hungry but losing weight. Very high levels with ketones cause vomiting and lethargy.

How can I check my dog for diabetes?

See your vet for blood and urine tests. Home tests aren't enough to diagnose it.

How quickly can a diabetic dog go blind?

Cataracts can form within days. Half of diabetic dogs develop them within about 6 months.

Do diabetic dogs pee a lot?

Yes. Increased urination is one of the main signs.

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Sources and further reading

This article was rewritten and fact-checked on October 23, 2026 against current veterinary references and specialist guidelines:

  1. AAHA Diabetes Management Guidelines for Dogs Task Force. Section 2: Recognizing and Diagnosing DM in Dogs. 2026 AAHA Diabetes Management Guidelines for Dogs, 2026.
  2. Bruyette D. Disorders of the Pancreas in Dogs. Merck Veterinary Manual (Dog Owners), updated May 2026.
  3. American Veterinary Medical Association. Diabetic Pets. AVMA owner brochure, revised 2010.
  4. Lee D. Lifting the Veil: Canine Cataracts and Cataract Surgery. MSPCA-Angell, 2026.
  5. Cornell Richard P. Riney Canine Health Center. Managing Canine Diabetes. Cornell University College of Veterinary Medicine.
  6. Buishand F. Diabetes Mellitus in Dogs and Cats. Merck Veterinary Manual, updated May 2026.
  7. Weir M, Williams K, Downing R, Ward E. Diabetes Mellitus in Dogs: Overview. VCA Animal Hospitals, updated January 2024.
  8. Hunter T, Williams K, Downing R. Diabetic Ketoacidosis in Dogs. VCA Animal Hospitals, updated June 2023.
  9. Coates J. Signs a Dog With Diabetes Is Dying. PetMD, 2022.
  10. Veterinary Practice. Treatment and management of canine diabetic cataract. Veterinary Practice.
  11. Heeley AM, O'Neill DG, Davison LJ, Church DB, Corless EK, Brodbelt DC. Diabetes mellitus in dogs attending UK primary-care practices: frequency, risk factors and survival. Canine Medicine and Genetics, 2020.
  12. University of Missouri College of Veterinary Medicine. Fanconi Syndrome. University of Missouri.
  13. AAHA Diabetes Management Guidelines for Dogs Task Force. Section 7: Troubleshooting in Diabetic Dogs. 2026 AAHA Diabetes Management Guidelines for Dogs, 2026.
  14. AAHA Diabetes Management Guidelines for Dogs Task Force. Section 3: Diabetic Ketoacidosis in Dogs. 2026 AAHA Diabetes Management Guidelines for Dogs, 2026.
  15. Canine and Feline Endocrinology, 4th ed. Chapter 1: Water Metabolism and Diabetes Insipidus. Elsevier Saunders, 2015.
  16. Kooistra H. The Diagnostic Approach to Polyuria in the Dog. EVC Voorjaarsdagen, Amsterdam (IVIS), 2013.
  17. AAHA Diabetes Management Guidelines for Dogs Task Force. Section 10: Other Methods for Monitoring Glycemic Status. 2026 AAHA Diabetes Management Guidelines for Dogs, 2026.

About this article

Last updated : fully rewritten using the 2026 AAHA Diabetes Management Guidelines for Dogs, the Merck Veterinary Manual, Cornell, veterinary ophthalmology sources and UK primary-care data, plus International Veterinary Information Service (IVIS) proceedings and research published 2022 to 2026.

This page is for general information and is not a substitute for an exam by your veterinarian.