A woman rang me a few winters back because her cat had started drinking out of the bathroom tap. Constantly. She asked if it was "just a weird phase," the way older cats sometimes pick up odd habits. It wasn't a phase. Bramble was eleven, carrying a bit of extra weight, and by the time she brought him in his blood glucose was well past what any healthy cat should show. He pulled through, but it took months of insulin, diet changes, and a lot of patience to get him stable. I think about that phone call every time someone mentions a cat drinking more than usual, because it's such an easy thing to write off.
Feline diabetes doesn't announce itself. It creeps in through small changes that look like normal aging, or normal cat weirdness, until suddenly they don't.
- What Actually Causes Diabetes in Cats
Most cats who develop diabetes have something close to human type 2 diabetes. Their bodies still produce insulin, at least early on, but the tissues stop responding to it properly. Glucose builds up in the blood instead of getting into the cells where it's needed. Left unmanaged, the pancreas eventually wears out trying to compensate, and insulin production drops too.
Obesity is the single biggest risk factor here, and it's not a minor one. A cat that's carrying significant extra weight is dramatically more likely to develop insulin resistance than a lean cat of the same age. Indoor cats with little to do all day, fed free-choice dry food, are the population I see this in most often. Age matters too. Diabetes is uncommon before seven or eight and becomes steadily more common after that. Burmese cats show up in the research more than their numbers would suggest, and some vets believe there's a genetic component in that breed specifically, though the picture there is still being worked out.
None of this means every overweight cat is doomed to become diabetic. It means the risk curve bends sharply once weight becomes a factor, and that's worth taking seriously long before any symptoms show up.
- The Early Signs Most Owners Miss
The frustrating thing about early diabetes is that the signs are quiet and easy to explain away. A cat drinking more could just be hot weather. Weight loss in an older cat gets chalked up to "cats lose weight as they age," which, to be fair, some do. Increased appetite looks like a good sign, not a warning one. That's exactly the trap.
Here's a rough guide to what tends to show up first, and why:
| Sign | What it looks like day to day | Why it happens |
|---|---|---|
| Increased thirst | Draining the water bowl faster, drinking from taps or puddles | Excess glucose pulls water out of tissues and into urine |
| Increased urination | Bigger clumps in the litter box, needing it changed more often | Kidneys are working overtime to flush out excess sugar |
| Weight loss despite eating well | Ribs becoming easier to feel, coat looking looser | Cells can't access glucose for energy, so the body burns fat and muscle instead |
| Ravenous appetite | Begging constantly, acting like it's never fed | The body is starving at a cellular level even with plenty of food coming in |
| Lethargy or weakness in the back legs | Reluctance to jump, a flat-footed walk on the hocks | Nerve damage from prolonged high glucose, seen in more advanced cases |
If you've noticed a change in the litter box lately and weren't sure what to make of it, cat-wonder has a piece specifically on litter box changes that actually signal something worth ruling out first, since not every change points to diabetes.
One thing that catches people off guard: a cat can look perfectly fine in the face. No obvious sickness in the eyes, no drama. And that's actually part of why this disease gets missed for so long, cats are extraordinarily good at masking that something is wrong until the problem has had real time to progress.
- Where People Get This Wrong
The most common mistake I see is treating increased appetite as reassuring. A cat that's suddenly eating like it's starving gets read as healthy and hungry, not as a cat whose cells can't use the food it's already getting. By the time weight loss becomes obvious enough to worry someone, the disease has usually been active for a while.
The second mistake, and this one runs the opposite direction, is assuming only overweight cats get diabetic, so a lean senior cat's excessive thirst gets attributed to something else, kidney disease usually, which does share some of the same symptoms. That's actually a fair concern since kidney disease and diabetes can look similar early on and sometimes occur together. This is exactly why symptoms like these need bloodwork rather than a guess based on body shape.
There's also a habit of dismissing early thirst changes because a stressed or anxious cat can show a temporary blood sugar spike from the stress of the vet visit itself. Vets are aware of this, it's called stress hyperglycemia, and it's why a single high glucose reading at a clinic isn't automatically a diagnosis. A fructosamine test, which reflects average blood sugar over roughly the past two to three weeks, gets around that problem and gives a much more reliable picture than a one-off glucose reading taken in an unfamiliar, stressful room.
- What To Do If You Notice These Signs
If you're seeing two or more of the signs above, the plan is straightforward, even if it's not always cheap or fast.
Book a vet visit and mention the specific changes you've noticed rather than a vague "something seems off." Specifics help a vet decide which tests to run first. Blood glucose, fructosamine, and a urinalysis checking for glucose and ketones in the urine are the standard starting point. If ketones show up alongside high glucose, that's an emergency, not a wait-and-see situation, because it points toward diabetic ketoacidosis.
Diet is the next lever, and it's a bigger one than most owners expect. Cats are obligate carnivores, and a lot of dry kibble is higher in carbohydrate than their bodies are built to handle well. Many vets now recommend a high-protein, low-carbohydrate wet diet for diabetic cats specifically because it takes pressure off the exact metabolic pathway that's struggling. Some cats diagnosed early and switched to this kind of diet, alongside insulin, actually go into remission, meaning they no longer need injections at all. That's genuinely more achievable in cats than it is in most diabetic dogs, and it's one of the more hopeful facts in this whole topic.
Home glucose monitoring is worth discussing with your vet too. Devices originally designed for continuous glucose monitoring in people are now used off-label in cats, stuck to a shaved patch of skin, and they cut down enormously on stressful repeat vet visits for blood draws. It's not required for every cat but it's changed how manageable this disease is for a lot of owners.
And if your cat is already a senior, this is one more reason twice-yearly checkups matter more than they did at five years old. We've written before about what those twice-yearly senior exams actually catch, and diabetes is exactly the kind of slow-moving problem that bloodwork catches months before symptoms would.
Bramble, the cat from that first phone call, ended up in partial remission about five months after diagnosis. Lower insulin dose, weight down to something reasonable, water bowl back to normal levels. His owner still checks his litter box out of habit now, which isn't a bad habit to keep, honestly. Most cats caught early do reasonably well. It's the cats caught late that struggle, and the gap between those two outcomes is usually just a few weeks of someone noticing something and not shrugging it off.
Frequently Asked Questions
Can a young cat get diabetes, or is this only an older-cat problem? It's uncommon but not impossible. The vast majority of cases show up in cats over seven, and risk climbs steadily from there, but a young, significantly overweight cat isn't automatically safe from it either.
Is weight loss always the first sign owners notice? Not usually. Increased thirst and litter box changes tend to show up first and get missed because they're subtle. Weight loss is often what finally makes someone book a vet visit, which means the disease has typically been active for a while by that point.
My cat's blood sugar was high at the vet but normal signs otherwise. Is that definitely diabetes? Not necessarily. Cats commonly show a temporary stress spike in blood glucose just from the visit itself. A fructosamine test or a repeat reading at home in a calmer environment gives a much clearer answer than one clinic reading alone.
Does every diabetic cat need insulin for life? No. A meaningful number of cats, especially those caught early and switched to an appropriate low-carbohydrate diet, achieve remission and come off insulin entirely. It's not guaranteed, but it's a realistic goal to discuss with your vet rather than assuming a lifetime commitment from day one.
What happens if diabetes goes untreated? It progresses toward diabetic ketoacidosis, a genuine emergency involving vomiting, extreme lethargy, and a sweet or acetone-like smell on the breath. This is not a wait-it-out situation and needs immediate veterinary care.
If any of this sounds familiar and you're weighing whether a vet visit is really necessary right now, it's worth reading through how often cats actually need vet visits before deciding to wait it out.
