Pet Diabetes 101: What Dog & Cat Owners Need to Know

By Dan Gray, DVM | Gentle Vet, Green Bay, Wisconsin

Your cat empties the food bowl and still looks thinner every month. Your dog drains the water dish twice a day and leaves puddles by the back door. Neither pet seems sick, exactly. Each owner assumes it’s age, a new routine, or a dog who needs more trips outside.

In our Green Bay exam rooms, those are the stories behind most new diabetes diagnoses. Diabetes mellitus is fatal without treatment, and in most households the disease becomes manageable once a routine settles in. Let’s discuss what diabetes does inside the body, how we confirm it, how treatment differs between dogs and cats, and which symptoms call for a same-day phone call.

What Is Diabetes in Dogs and Cats?

When a pet eats, digestion sends a burst of sugar into the bloodstream. Insulin, a hormone made in the pancreas, works like a key that moves that sugar into the cells, where the sugar serves as fuel. Diabetes mellitus means the body lacks enough insulin, or cannot use the insulin it makes. The key is missing, so the sugar stays in the blood and the cells go hungry.

“Even though your pet is eating, the food never makes it to the cells where it needs to go. It just stays in the bloodstream. Then the kidneys do their job and filter out all the excess sugar, which used to be food.”

— Dr. Dan Gray, Gentle Vet

That filtered sugar drags water along with it, so urine volume climbs and thirst climbs to match. The result is the pattern owners describe: a pet who eats and eats and drinks and drinks, yet is “starving internally,” in the words of our own Dr. Gray.

Dogs and cats reach this point by different roads. The 2026 AAHA guidelines for dogs describe canine diabetes as permanent loss of insulin-producing cells, most often in middle-aged to older dogs. Cats more often develop a disease tied to body weight and insulin resistance, and Cornell’s Feline Health Center reports that overweight cats are up to four times more likely to become diabetic. That difference matters later: some cats recover enough to stop treatment, while remission is rare in dogs.

How Do We Diagnose Diabetes in a Pet?

Our standard workup is a complete blood count, a chemistry panel, and a urinalysis, plus a thyroid test in many cats. Those tests confirm the diagnosis and screen for infection, kidney or liver disease, and hormone problems that change the plan. The urinalysis also checks for ketones, acids the body makes when it burns fat for fuel, because the result decides which medications are safe. Routine lab work can catch high blood sugar before symptoms start, which is why we recommend regular screening for older dogs and cats (see The Importance of Lab Work Through Your Dog’s Life).

The hallmark in both species is high blood sugar together with sugar in the urine. Glucose spills into the urine once blood levels pass the kidneys’ threshold, roughly 250 to 300 mg/dL in cats according to the AAHA cat guidelines. In dogs, AAHA’s diagnostic criteria call for a blood glucose of at least 200 mg/dL, sugar in the urine, and classic symptoms.

Cats complicate the picture, because a frightened cat on an exam table can post a very high number. As a rule of thumb, readings persistently above 300 put a cat in diabetic territory, yet we have seen a couple of stressed cats approach 400 mg/dL with no diabetes at all. A quick stress spike rarely reaches the urine fast enough to detect, so high blood sugar with normal urine sugar usually points to stress, not diabetes. When the answer stays unclear, we run a fructosamine test. Fructosamine reflects average blood sugar over roughly the previous two weeks, so a nervous car ride cannot fake it.

How Is Diabetes Treated, and Why Do Dogs and Cats Differ?

Every diabetic pet receives a custom plan built on insulin support, a steady diet, and verified numbers. The details split by species, and our general medicine team manages the rechecks.

Treating a Diabetic Dog

Every diabetic dog needs insulin. We typically use Vetsulin (porcine insulin zinc suspension), one of the first-choice options in the 2026 AAHA dog guidelines, and the American Veterinary Medical Association notes that injections usually go in twice a day. We pair insulin with a high-fiber diet for most dogs, since added fiber can blunt the sugar surge after meals, when fed at consistent times.

We strongly recommend a FreeStyle Libre continuous glucose monitor, a small sensor worn on the skin, if the dog will tolerate one. The sensor reports glucose around the clock, and we keep using it until the dog is regulated, usually two to six weeks. Even a few days of sensor data are usually more helpful than a standard in-hospital glucose curve, according to AAHA. When an owner declines a sensor, we check fructosamine about once a month and adjust the insulin dose to match.

Treating a Diabetic Cat

Food comes first for cats. A severely carbohydrate-restricted diet is, as Dr. Gray puts it, “an incredibly effective tool.” The AAHA cat guidelines recommend high-protein food with carbohydrates around 12% of calories, and they favor canned food over dry.

Next comes the medication decision. A cat that has just been diagnosed, has never received insulin, is eating and well hydrated, and has no ketones in the urine can start an oral medication given once a day. Two are FDA-approved for exactly that group: Senvelgo, a liquid, and Bexacat, a tablet (see the FDA labels for Senvelgo and Bexacat). Both labels warn about ketoacidosis, a dangerous buildup of ketones. The AAHA guidelines report that the problem occurs in roughly 5 to 7% of treated cats, mostly within the first two weeks, which is why we screen for ketones before starting and recheck early.

Cats with ketones, or cats who don’t meet those criteria, start on insulin instead. Insulin glargine (Lantus) is our usual choice, paired with the same diet. A continuous glucose monitor helps again during stabilization. Without one, we check fructosamine every three to four weeks and adjust the dose. We rarely rely on glucose curves in the hospital, because stress inflates the numbers and the cost adds up, and most owners cannot run curves at home either. AAHA no longer recommends routine in-hospital glucose curves for cats.

Can diet alone fix it? Sometimes. A cat with the weight-related form can gain a lot of long-term control from food, but the vast majority eventually need insulin, and we prepare owners for that. Remission is a real goal: AAHA puts the average remission rate in the United States near 30%, while noting that remission is not a cure and relapse is common (AAHA remission section). Cornell adds that a cat not in remission within about six months will almost certainly need insulin for life. In dogs, diet cannot replace insulin, and we have never seen a diabetic dog fixed with diet.

Is Pet Diabetes a Death Sentence?

Owners ask us this at nearly every diagnosis, and we answer it plainly.

“If we choose to do nothing or we are unable to do anything, if this remains untreated, this will be fatal. It is very manageable, but it’s not possible for everybody.”

— Dr. Dan Gray, Gentle Vet

Treatment is a commitment, usually twice a day, for the rest of the pet’s life. If a household cannot give that care and the pet cannot be rehomed, then surrender or euthanasia can be a reasonable choice, because an untreated diabetic pet suffers and dies. We make sure people understand this at diagnosis so nobody is blindsided later.

Most households never face that decision. Fear of needles comes up often, so we offer to practice with saline instead of insulin, on your pet or on Queenie, our clinic dog, until the first pokes feel ordinary. We also encourage owners to ask a spouse, a grown child, or a friend to give the injections if the idea is too hard. The 2026 AAHA dog guidelines describe the outlook as favorable with proper treatment and monitoring, and note that most dogs remain controlled once insulin therapy is established.

Once owners find their groove and understand that insulin doses sometimes need adjusting as blood sugar shifts through life, most become success stories. We once saw a family adopt two completely unrelated dogs, and both were diagnosed with diabetes within a few months of each other. That coincidence is unusual, but the owner sought treatment immediately, and both dogs did well.

What Should Owners Watch for After Treatment Starts?

Untreated disease remains the biggest danger. Once insulin begins, however, low blood sugar (hypoglycemia) is by far the most dangerous problem, and the cause is rarely a skipped meal. In Dr. Gray’s experience it is “less from a skipped meal than it is from owners adjusting insulin on their own without understanding.” AAHA’s client education guidance is blunt about it: never increase the insulin dose or how often it is given without clear instructions from your veterinarian (AAHA dog guidelines, client education).

Continuous glucose monitors add a wrinkle. A sensor measures sugar in the fluid under the skin, and that reading can trail behind the blood. A sensor that reads low in a pet who is eating, moving, and acting normal is probably not an emergency, and AAHA recommends confirming low sensor readings with a veterinary-calibrated blood glucose meter before changing any treatment (AAHA cat guidelines, glucose monitoring). A pet who is acting sick is different.

Long-term complications look different in each species. Dogs often develop diabetic cataracts: a North Carolina State study of 200 diabetic dogs found that about 80% had developed them within 16 months of diagnosis (Beam et al., 1999). Cats can develop nerve damage in the hind legs that makes them walk with the hocks close to the ground, called a plantigrade stance, and the same nerve damage can make a diabetic cat hesitate at the litter box or miss it (our guide to litter box behavior covers other causes). We look for both at every recheck.

Pet Diabetes FAQ

What are the early symptoms of diabetes in dogs and cats?

The most common early symptoms of diabetes in dogs and cats are weight loss despite a normal or increased appetite, increased thirst, and increased urination, often with accidents in the house. Some diabetic pets also have low energy, and dogs may develop cloudy eyes. Some owners notice nothing until a veterinarian finds high blood sugar on routine lab work.

How can a vet tell diabetes from stress in a cat?

A veterinarian looks for sugar in the urine along with high blood sugar. Stress can push a cat’s blood sugar very high during a visit, but the urine usually stays normal because the spike is too brief. When the result is unclear, a fructosamine test shows average blood sugar over roughly two weeks and separates true diabetes from a stress reaction.

Can diabetes in cats go away?

Some diabetic cats go into remission and stay healthy without insulin, but remission is not a cure. AAHA reports an average remission rate of about 30% in the United States, and relapse is common. Cats that do not reach remission within about six months usually need insulin for life. Remission is rare in dogs.

Can diet alone treat diabetes in dogs or cats?

Diet alone does not treat diabetes in dogs, and every diabetic dog needs insulin. In cats, a canned, very low carbohydrate diet can provide a great deal of long-term control, and it is the first step in treatment, but most diabetic cats eventually need insulin or an approved oral medication as well.

How often does a diabetic dog or cat need medication?

Insulin injections for diabetic dogs and cats are usually given twice a day, about twelve hours apart. A newly diagnosed cat that qualifies for an oral medication such as Senvelgo or Bexacat takes it once a day. Gentle Vet in Green Bay picks the option after an exam, blood work, and a urinalysis that includes a ketone check.

What should I do if my diabetic pet seems weak or unresponsive?

Call a veterinarian immediately. Weakness, glassy eyes, unresponsiveness, tremors, vomiting, or a seizure in a diabetic pet can mean dangerously low blood sugar, and an actual blood sugar check is needed. While you arrange care, an awake pet can be given a small amount of corn syrup rubbed on the gums, followed by a little food once it can swallow, but do not wait for that to work before heading in. Do not change the insulin dose at home without instructions from your veterinarian. In Green Bay, call Gentle Vet at 920.435.5000 during business hours or an emergency hospital after hours.

Drinking More, Urinating More, and Still Losing Weight?

Those three changes deserve a blood and urine test now, not a wait-and-see. We run lab work in-house, usually with results the same day, so we can talk through a plan before you head home. Already living with a diabetic dog or cat and sensing the numbers drift? Book a recheck rather than adjusting a dose at home. We serve pet owners from De Pere and Ashwaubenon to Allouez and across Northeast Wisconsin.

Gentle Vet Animal Hospital

2560 University Ave, Green Bay, WI

(920) 435-5000

www.thegentlevets.com

[email protected]

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