Diabetes in Dogs: The Early Signs Owners Miss

A Burlington owner calls the front desk, a little sheepish. Their ten-year-old dog has been draining the water bowl and asking to go out at 2 a.m., and they figured it was just getting older.

We hear this one a lot on Brant Street. The dog seems fine at home.

Bright, happy, eating well, maybe even eating a bit more than usual.

That last detail is the one that matters most. When a dog drinks more, pees more, and loses weight while cleaning the bowl, the body is sending a signal worth checking.

The early signs of diabetes in dogs are increased thirst, increased urination, increased appetite, and weight loss, according to Cornell’s Riney Canine Health Center. The Merck Veterinary Manual notes these signs come on slowly over weeks to months, which is exactly why they slip past even attentive owners at first.

If this is happening right now: your dog is weak, lethargic, vomiting, not eating, or dehydrated. According to Cornell’s Riney Canine Health Center, untreated diabetes can progress to diabetic ketoacidosis, a life-threatening emergency. Call us at (905) 336-4002, the Pet Poison Helpline at 855-764-7661, or the ASPCA Animal Poison Control Center at 888-426-4435, and you can reach an emergency team through our after-hours care page.

What are the first signs of diabetes in a dog?

The first signs are the classic four: more thirst, more urination, a bigger appetite, and weight loss, per Cornell’s Riney Canine Health Center. In our exam rooms on Brant Street, the water bowl and the overnight bathroom trips are usually what owners notice first, often before anything else looks wrong.

Here is the tricky part. None of these signs shout.

A dog who drinks a little more each week, or asks to go out one extra time a night, looks like a dog who is simply getting older.

Cornell’s Riney Canine Health Center explains that diabetes in dogs comes from a deficiency of insulin, the hormone the pancreas uses to move sugar out of the blood and into cells. Without enough of it, blood sugar climbs.

Once blood glucose passes roughly 180 mg/dL, sugar starts spilling into the urine, a change vets call glucosuria (sugar in the urine), according to Merck. The normal fasting range sits around 75 to 120 mg/dL.

If two or three of these line up, that is the moment to book a visit. A quick blood and urine screen in our diagnostics lab can sort out a passing phase from something that needs treatment.

Can a dog with diabetes still eat normally and have a big appetite?

Yes, and this is one of the most confusing parts for owners to make sense of. A diabetic dog often eats normally, or even more than usual, while still losing weight, according to the Merck Veterinary Manual, so a good appetite does not put diabetes to rest.

The mechanism is worth understanding. Merck explains that without enough insulin, the body cannot pull glucose into its cells for fuel.

So the body does the next best thing. It starts breaking down fat for energy, which drains weight off a dog even as the food bowl keeps emptying.

That is why “he is eating great, but he looks thinner” is a sentence we take seriously. A hearty appetite does not rule diabetes out.

Paired with more drinking and more peeing, it can actually point toward it, and it is worth a call to our team rather than a wait-and-see.

What breeds and ages of dogs are most likely to get diabetes?

Middle-aged dogs are affected most commonly, and female dogs are affected about twice as often as males, according to the Merck Veterinary Manual’s owner guide. Several small breeds also seem to develop it more often than others, though the same guide notes that any breed can be affected.

Merck lists Miniature Poodles, Dachshunds, Schnauzers, Cairn Terriers, and Beagles among the more predisposed breeds. So a mixed-breed senior is far from exempt.

This is where the local angle matters. Because diabetes tends to show up in middle-aged and older dogs, and because Merck notes the signs build slowly, a Burlington dog around 7 and up is exactly the patient we like to screen before symptoms get loud.

Pairing a physical exam with a baseline glucose and urine check during a senior wellness visit is how subtle changes get caught early, through the leaf-raking and first-frost weeks of a Halton autumn and into winter.

Is diabetes in dogs caused by being overweight?

Not on its own, but weight plays a real role: the Merck Veterinary Manual notes that obesity increases insulin resistance, meaning the body works harder to get the same job done from its insulin. Cushing’s disease, pancreatitis, and certain long-term medications are listed as risk factors too, so weight is just one piece.

The root cause, though, sits with insulin itself. Cornell’s Riney Canine Health Center describes diabetes as a deficiency of the hormone insulin, which lets sugar build up in the bloodstream rather than feeding the cells.

So a lean dog can still become diabetic, and a heavier dog is not guaranteed to. A healthy weight simply stacks the odds in your dog’s favour and makes any future diabetes easier to manage.

If your dog has crept up on the scale, our nutrition and weight management team can build a plan that fits your household.

How is diabetes in dogs diagnosed?

Diabetes is diagnosed by finding high levels of sugar in both the blood and the urine, usually alongside the clinical signs, according to the Merck Veterinary Manual. Cornell adds that the picture comes together from clinical signs combined with blood work and a urinalysis.

One test helps in tricky cases. Cornell notes that stress alone can briefly raise a dog’s blood sugar, especially in a nervous patient at the clinic.

To tell a stress spike from true diabetes, Cornell notes vets can run a blood fructosamine level, a test that reflects average blood sugar over the previous couple of weeks rather than a single moment. For Burlington families, this workup is routine: a morning drop-off, a quick blood draw, and a urine sample usually get clear answers.

Does diabetes cause cataracts and blindness in dogs?

Cataracts develop frequently in dogs with poorly controlled diabetes, according to the Merck Veterinary Manual, which is why any cloudiness in a diabetic dog’s eyes gets our attention. Merck links those cloudy lenses to vision loss, so it is something we check for and talk through with owners at every visit.

The numbers are striking. In a retrospective study of 200 diabetic dogs by Beam, Correa, and Davidson, about half had developed cataracts by 170 days after diagnosis, 75% by 370 days, and 80% by 470 days, roughly 16 months.

That timeline is one of the strongest arguments for catching diabetes early and keeping blood sugar steady. The better the day-to-day control, the more you tilt the odds against a fast slide toward vision loss.

What happens if a dog’s diabetes goes untreated?

Left untreated, diabetes can turn dangerous: Cornell’s Riney Canine Health Center warns that it can progress to diabetic ketoacidosis, or DKA, a life-threatening emergency marked by weakness, lethargy, poor appetite, vomiting, and dehydration. That is the situation that belongs in our critical care room, not a wait-until-morning plan.

There are slower harms too. The Merck Veterinary Manual notes that diabetic dogs have decreased resistance to infection and often develop chronic or recurrent problems such as bladder infections (cystitis), skin infections (dermatitis), prostatitis, and pneumonia.

Merck also describes an enlarged liver, called hepatomegaly, from fat building up in the organ as a common finding in diabetic dogs. None of this is meant to frighten you; it is meant to explain why treatment matters.

The tools are well established. Cornell calls insulin the cornerstone of treatment, given as a small under-the-skin injection twice a day at mealtimes, and notes that most diabetic dogs need it for life but can be managed to a good quality of life.

This article is educational and isn’t veterinary advice or a substitute for an exam. If you’re worried about your pet right now, call us at (905) 336-4002 or your nearest emergency veterinary hospital.

If your dog is middle-aged or older and you have noticed the water bowl emptying faster than it used to, a simple senior wellness check can put your mind at ease. Our team on Brant Street is glad to take a look and talk it through with you.

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Frequently asked questions

Can diabetes in dogs be cured or reversed?

Canine diabetes generally is not cured. Cornell’s Riney Canine Health Center notes most diabetic dogs need lifelong insulin, given as a small under-the-skin injection twice a day at mealtimes. The encouraging part is that with steady treatment and monitoring, the disease can be managed so a dog keeps a good quality of life.

How long can a dog live with diabetes?

Many diabetic dogs live full, comfortable lives once treatment settles into a routine. Cornell reports that with lifelong insulin and regular monitoring, diabetes can be successfully managed to give a dog a good quality of life. Early diagnosis and consistent follow-up visits make the biggest difference, so call us if you notice the early signs.

What is the earliest change I might notice at home?

Usually the water bowl. The Merck Veterinary Manual notes signs progress slowly over weeks to months, and increased thirst and urination are often the first things owners spot. A dog draining the bowl, asking out overnight, or having accidents after being reliably house-trained is worth a call to our team on Brant Street.

Should my senior dog get bloodwork even if she seems healthy?

It can be a smart move. Because canine diabetes usually shows up in middle-aged and older dogs and creeps in slowly, per Merck, a baseline blood glucose and urinalysis during a senior wellness exam can catch changes early. For Burlington dogs around 7 and up, we often pair the physical exam with simple screening.

Can diabetes lead to other infections?

Yes. The Merck Veterinary Manual reports diabetic dogs have decreased resistance to infection and often develop chronic or recurrent problems such as bladder infections, skin infections, prostatitis, and pneumonia. A urinary tract infection that keeps coming back can sometimes be the clue that sends us looking at blood sugar in the first place.

Sources

Veterinary medical references

1. Cornell University College of Veterinary Medicine, Riney Canine Health Center: Diabetes in Dogs
2. Merck Veterinary Manual (professional): Diabetes Mellitus in Dogs and Cats
3. Merck Veterinary Manual (dog-owner version): Disorders of the Pancreas in Dogs

Peer-reviewed research

1. Beam S, Correa MT, Davidson MG: A retrospective-cohort study on the development of cataracts in dogs with diabetes mellitus, 200 cases, Veterinary Ophthalmology.

Emergency and poison control

1. Pet Poison Helpline: 855-764-7661
2. ASPCA Animal Poison Control Center: 888-426-4435