Early Signs of Diabetes in Cats: Why Increased Thirst and Weight Loss Matter

If your cat has started draining the water bowl, leaving heavier clumps in the litter tray, and feels lighter in your arms despite finishing every meal, diabetes belongs high on the list of possible explanations. The early signs of diabetes in cats are quiet and easy to explain away as ageing or warm weather, which is why many cats are only diagnosed once they are seriously unwell. Caught early, this is a manageable disease, and some cats even stop needing medication altogether. This guide will help you recognise the pattern, measure what your vet needs to know, and understand when a thirsty cat becomes an emergency.

What is diabetes doing inside your cat's body?

Most diabetic cats have a condition similar to type 2 diabetes in people. The pancreas either makes too little insulin or the body stops responding to it properly, so glucose (sugar) stays in the bloodstream instead of entering cells.

Two things follow, and they explain almost every sign you will notice at home:

• Once blood sugar rises above what the kidneys can hold back, glucose spills into the urine and drags water with it. Your cat urinates more, then drinks more to keep up.
• Cells starved of fuel start burning fat and muscle instead. Your cat loses weight while still eating, and sometimes eats more than ever.

Diabetes is one of the most common hormonal diseases in cats. The International Society of Feline Medicine puts the number at roughly 1 in 100 to 1 in 500 cats seen in general practice, and cases appear to be rising alongside feline obesity.

What are the early signs of diabetes in cats?

The four classic signs described in the ISFM and iCatCare consensus guidelines are increased urination, increased thirst, weight loss and lethargy, often with a hearty appetite.

Drinking more than usual

This is often the first thing owners spot. You are refilling the bowl more often, your cat starts drinking from the tap, the shower tray, a watering can or the toilet, or a cat who never showed interest in water now sits by it.

Cats fed wet food normally drink very little, because tinned food is about 75 to 80% water. A cat on wet food who suddenly develops a real thirst is worth taking seriously, even if the total volume still looks modest.

Larger and heavier litter clumps

Owners frequently notice the tray before they notice the water bowl. You may be scooping bigger clumps, changing litter more often, or finding puddles outside the tray from a cat who simply cannot hold on. Some cats start urinating on beds or carpets.

There is a distinction that matters here: passing large volumes is a diabetes clue, while squatting repeatedly, straining and producing only a few drops points instead to a bladder problem. Straining to urinate in a male cat is an emergency in its own right.

Weight loss with a normal or increased appetite

This combination is the one that should really prompt a phone call. A cat who is losing weight while eating well is burning body tissue, and diabetes, an overactive thyroid and intestinal disease are the usual reasons. Long fur hides a great deal, so a cat can lose 10% of their body weight before it becomes visible.

The subtler changes

• Coat looking dull, greasy or unkempt because grooming has slipped
• Sleeping more, jumping onto furniture less, playing less
• A hind-limb stance that looks dropped, with the ankles sinking towards the floor (plantigrade stance). This comes from nerve damage caused by prolonged high blood sugar and means the diabetes has been present for some time
• Weakness in the back legs, or a reluctance to use stairs

How much water is too much for a cat?

Vets use a working threshold: intake above 100 ml per kilogram of body weight per day is considered definite excessive drinking (polydipsia). For a 4 kg cat, that is more than 400 ml in 24 hours. Anything in the range of roughly 60 to 100 ml/kg/day sits in a grey zone that still deserves attention, especially if it is clearly more than your cat used to drink.

Because normal intake varies with diet, weather and activity, a change from your cat's own baseline is more meaningful than any single number.

How to measure it properly:

1. Pick a 24-hour period on a normal day, not during a heatwave.
2. Fill the bowl with a measured amount using a kitchen measuring jug.
3. Top up only with measured amounts, and note each one.
4. Measure what is left after 24 hours, and subtract it. Allow for evaporation by leaving an identical bowl of water somewhere your cat cannot reach and subtracting that loss too.
5. Repeat over two or three days, since intake bounces around.

In a multi-cat household this gets difficult. Do your best, note how many cats have access, and tell your vet you could not separate them. Block off other water sources during the test if you safely can.

One rule with no exceptions: never restrict your cat's water to reduce the urination. A diabetic cat is drinking because they are losing fluid, and taking water away will cause dangerous dehydration fast.

Why does the weight loss matter so much?

Weight loss tells you the disease is already affecting your cat's body, and it predicts a harder recovery. The 2025 iCatCare guidelines point out that diagnosing and treating diabetes early improves the chance of remission and helps cats avoid significant weight loss and complications.

Muscle is not easy to rebuild in an older cat. The lighter and weaker a cat becomes before treatment starts, the longer they take to bounce back.

Weighing at home takes 30 seconds and beats guessing:

• Use baby scales, or a kitchen scale with the carrier: weigh the carrier with your cat inside, then weigh the empty carrier and subtract.
• Do it once a month and write it down with the date.
• Treat a drop of 5% or more as a reason to book an appointment. For a 5 kg cat, that is 250 g. A 500 g loss in a 5 kg cat is like a 70 kg person losing 7 kg.

Body condition matters as much as the number. Run your hands over the ribs and spine: in a cat at a healthy weight you can feel the ribs easily under a thin fat layer, without seeing them.

Which cats are most likely to develop diabetes?

Risk goes up with:

• Age: increasing age is the strongest single risk factor, with most cats diagnosed after 8 years and cases peaking around 10 to 13 years
• Being overweight: excess body fat drives insulin resistance and is the risk factor you can actually change
• Being male and neutered: male cats are consistently over-represented
• An indoor, inactive lifestyle
• Breed: Burmese cats of European lines carry a higher risk than the general cat population
• Certain medications: long courses of steroids and some progestogens raise blood glucose

None of this means a slim, young, female cat cannot become diabetic. It just changes how quickly the possibility should come to mind.

When to call the vet

Book a routine appointment within the next few days if your cat is drinking noticeably more, urinating more, has lost weight, or seems flatter than usual. Bring your water measurements and weight notes.

Treat it as an emergency and seek same-day veterinary care if a thirsty, weight-losing cat shows any of these:

• Refusing food, or a sudden loss of appetite in a cat who was previously ravenous
• Vomiting
• Marked weakness, wobbliness, or an inability to stand
• Fast or laboured breathing
• Breath that smells sweet or like nail polish remover
• Collapse, or being unresponsive and difficult to rouse

That combination suggests diabetic ketoacidosis, a metabolic crisis that develops in untreated or poorly controlled diabetic cats. The ISFM guidelines list depression, loss of appetite, vomiting, weakness and collapse as the signs that should raise suspicion. With prompt hospital treatment, including fluids and insulin, many cats pull through. Untreated, it is fatal. Do not wait for morning.

Already-diagnosed cats have one extra emergency: a wobbly, disoriented, trembling or seizing cat may have blood sugar that has fallen too low. If your cat is conscious and can swallow, rub a little honey or glucose syrup onto the gums and phone your vet immediately.

What happens at the vet appointment?

Diagnosis is usually straightforward, though it can take more than one visit. Expect:

• A full physical exam, weight and body condition score
• Blood glucose, plus fructosamine, which reflects average glucose over the preceding weeks. This second test matters because stress alone can raise a cat's blood sugar in the clinic, and a stressed cat's single reading can be misleading
• A urine sample checked for glucose, ketones and infection
• Wider blood work, since kidney disease, an overactive thyroid, pancreatitis and urinary infections cause similar signs or occur alongside diabetes

Increased thirst, urination and weight loss are not specific to diabetes. In cats, the three most common causes of that pattern are chronic kidney disease, diabetes and hyperthyroidism, and they need very different treatments. That is why the diagnosis has to come from tests, not from a symptom list.

What does treatment involve?

Most cats do well. Options now include:

• Insulin injections: usually twice daily under the skin with a very fine needle. Most owners are surprised how quickly cats accept it and how quickly they learn the technique
• Oral SGLT2 inhibitor tablets or liquid: bexagliflozin and velagliflozin are given once daily and licensed for newly diagnosed diabetic cats who are otherwise well and have not had insulin. They make the kidneys excrete surplus glucose. They are not suitable for every cat, and close monitoring in the first two weeks is important
• Diet: current recommendations favour high-protein, low-carbohydrate food, which improves glucose control and may raise the chance of remission
• Weight management: gradual, vet-supervised weight loss in overweight cats reduces insulin resistance

Remission, meaning normal blood sugar without medication, is a realistic goal for some cats, and the odds are better the earlier treatment begins. Even cats who need lifelong medication can live comfortably for years.

How can you lower the risk in the first place?

• Keep your cat lean. This is the single biggest lever you have
• Measure meals rather than free-feeding, and count treats in the daily total
• Build in daily play and food puzzles, particularly for indoor cats
• Weigh your cat monthly and act on trends instead of waiting for the annual check
• Have cats over 7 examined at least yearly, with blood and urine screening, and discuss extra monitoring if your cat needs long-term steroids

The takeaway

A cat who drinks more, urinates more and is quietly losing weight is telling you something specific, and diabetes is one of the most treatable answers on the list. Measure the water, note the weight, and get those numbers in front of a vet rather than waiting to see whether things settle. Cats diagnosed while they are still bright and eating do far better than cats diagnosed in crisis, and this guide is meant to help you have that conversation sooner, not to replace the examination and tests your vet needs to do.