A cat drinking noticeably more water than usual is almost always signaling a medical problem. Healthy cats drink roughly 4 ounces of water per 5 pounds of body weight each day, so a 10-pound cat would normally consume about 8 ounces. If your cat is consistently exceeding that, or if you’re refilling the water bowl more often than you used to, something is driving that thirst. The three most common causes are kidney disease, diabetes, and hyperthyroidism, all of which are treatable, especially when caught early.
How Much Water Is Too Much?
Veterinarians define excessive drinking in cats as more than 45 milliliters per kilogram of body weight in 24 hours. For a typical 10-pound (4.5 kg) cat, that works out to roughly 6.8 ounces, or just under a full cup. Anything consistently above that range warrants attention. The tricky part is that most cat owners don’t measure their cat’s water intake precisely. What usually gets noticed instead is a pattern: the bowl empties faster, the cat starts drinking from faucets or toilets, or the litter box becomes heavier and wetter than normal.
One simple thing to check before worrying is your cat’s diet. Dry kibble is only about 10% water, while canned food is roughly 70% water. A cat that recently switched from wet food to dry food will naturally drink significantly more from the bowl to make up the difference. That’s not a medical issue. But if nothing about the diet has changed and your cat is clearly drinking more, the cause is almost certainly internal.
Kidney Disease
Chronic kidney disease is the single most common reason older cats start drinking excessively. Healthy kidneys concentrate urine, pulling water back into the body so it isn’t lost. As kidney tissue deteriorates, that concentrating ability breaks down. The cat produces large volumes of dilute urine and then drinks more to replace the lost fluid. The increased drinking isn’t the disease itself; it’s the cat’s attempt to keep up with water loss.
What makes kidney disease deceptive is how long it hides. Standard blood markers like creatinine don’t rise until a cat has lost roughly 75% of kidney function. A newer marker called SDMA can flag problems earlier, when about 40% of function is gone, which is one reason veterinarians now include it in routine senior bloodwork. By the time you notice your cat drinking more, the disease may already be moderately advanced. Cats with kidney disease often lose weight gradually, eat less, and sometimes vomit more frequently. The disease is progressive, but early detection and dietary management can slow it significantly and keep a cat comfortable for years.
Diabetes
Diabetes in cats works similarly to type 2 diabetes in humans. The body either doesn’t produce enough insulin or stops responding to it properly, so blood sugar climbs. When glucose levels get high enough, the kidneys can no longer filter it all back into the bloodstream. Sugar spills into the urine and, because of its chemical properties, pulls extra water along with it. The result is heavy urination followed by intense thirst.
Cats with diabetes typically drink and urinate far more than normal. They often eat ravenously but still lose weight, because their cells can’t access the energy in their food without adequate insulin. Diabetes is most common in overweight, middle-aged, and senior cats. Unlike kidney disease, feline diabetes is sometimes reversible. With early treatment, some cats regain normal blood sugar regulation and no longer need ongoing therapy.
Hyperthyroidism
An overactive thyroid gland is extremely common in cats over 10 years old. The gland produces excess thyroid hormone, which ramps up the body’s metabolic rate. This affects nearly every organ system and creates a recognizable cluster of symptoms: weight loss despite a good or even increased appetite, increased thirst and urination, vomiting, diarrhea, and hyperactivity. Affected cats may also develop a coat that looks greasy, matted, or unkempt.
Hyperthyroidism is usually straightforward to diagnose with a blood test and has several effective treatment options. Left untreated, it can cause secondary heart and kidney problems, so it’s worth investigating promptly if your older cat is drinking more and losing weight at the same time.
Less Common but Serious Causes
Liver disease can also drive increased thirst in cats and tends to appear in middle-aged or senior animals. Symptoms may include poor appetite, yellowing of the gums or inner ears, and lethargy.
For unspayed female cats, a life-threatening uterine infection called pyometra should be on the radar. Pyometra causes the uterus to fill with bacteria and pus. Affected cats may show increased thirst and urination alongside lethargy, poor appetite, vomiting, a distended belly, or vaginal discharge. This is a medical emergency. Without prompt treatment, pyometra can cause sepsis and death. If your unspayed female cat suddenly starts drinking excessively and seems unwell, don’t wait to see if it resolves on its own.
Urinary tract infections, certain medications (particularly corticosteroids), and high-calcium conditions can also increase water intake, though these are less frequently the primary culprit in cats.
Could It Be Behavioral?
In dogs, stress or boredom occasionally causes compulsive water drinking with no underlying medical cause. In cats, this essentially doesn’t happen. Psychogenic polydipsia, as it’s formally called, has not been reliably documented in cats. If your cat is drinking excessively, assume a physical cause until proven otherwise. Behavioral explanations should only be considered after thorough testing has ruled out every medical possibility.
What Happens at the Vet
A veterinarian investigating excessive thirst will typically start with bloodwork and a urinalysis. Together, these two tests can identify or rule out most of the common causes, including kidney disease, diabetes, hyperthyroidism, and liver problems, often in a single visit.
One of the most useful pieces of the urinalysis is a measurement called urine specific gravity, which tells the vet how concentrated or dilute the urine is. In a healthy cat, urine specific gravity should be above 1.035, reflecting the kidneys’ ability to conserve water. A consistently low reading suggests the kidneys aren’t concentrating urine properly, which narrows the list of possible causes. If basic bloodwork and urinalysis don’t reveal the answer, your vet may recommend a urine culture to check for hidden infections or additional targeted tests.
Before your appointment, it helps to have a rough sense of how much your cat is actually drinking. Try measuring the water you put in the bowl each morning and checking what’s left at the end of the day (accounting for evaporation and other pets). Even an approximate number gives your vet useful information.
Why Timing Matters
Increased thirst in cats is rarely a quirk and almost never resolves on its own. The conditions that cause it, particularly kidney disease and diabetes, respond best to early intervention. Kidney disease diagnosed at an earlier stage can be managed with dietary changes and supportive care that meaningfully extend a cat’s life. Diabetes caught before a cat becomes severely ill has the best chance of remission. Hyperthyroidism is highly treatable at any stage but causes less organ damage the sooner it’s addressed.
If your cat has been drinking noticeably more for a few days and nothing about their diet or environment has changed, that’s enough reason to schedule an exam. If excessive thirst comes with weight loss, vomiting, lethargy, or changes in appetite, move the timeline up.