Why Is My Cat Drinking More Water? (CKD Warning Sign)

You've noticed something different about your cat. Maybe the water bowl empties faster than it used to. Maybe you keep finding your cat at the faucet, begging for dripping water. Or maybe the litter box clumps have gotten noticeably bigger — so big that you're using more litter than ever. These are all signs of increased thirst (polydipsia) and increased urination (polyuria), and in a cat — especially an older cat — they are among the earliest and most important warning signs of chronic kidney disease.

Catching CKD early gives you the most options for treatment and the best chance of slowing its progression. This article explains why CKD causes increased thirst, how to tell if your cat is truly drinking too much, what other conditions it could be, and exactly what to tell your vet to get the fastest, most accurate diagnosis.

Why CKD Causes Increased Thirst

To understand why CKD makes cats drink more, it helps to understand what kidneys normally do. Healthy kidneys act as sophisticated filters that remove waste from the blood while simultaneously conserving water. They do this by concentrating urine — pulling water back into the body so that waste is excreted in a minimal amount of fluid. A healthy cat produces small amounts of concentrated urine.

When kidneys begin to fail, they lose this ability to concentrate urine. Instead of producing small amounts of concentrated urine, the cat produces large amounts of dilute urine. This means the cat is losing water rapidly through urination, which leads to dehydration. The body responds to this dehydration by triggering thirst — the brain sends a powerful signal to drink more water to replace what's being lost.

This is why the two symptoms almost always appear together: increased urination (you notice bigger clumps in the litter box) and increased drinking (the water bowl empties faster). It's a direct consequence of the kidneys losing their water-conserving ability, and it's one of the first externally visible signs of CKD.

How Much Water Is Too Much?

A healthy cat typically drinks about 50-60 mL of water per kilogram of body weight per day. For a 4 kg (9 lb) cat, that's about 200-240 mL — roughly one standard cup. However, cats that eat wet food get a significant portion of their water from their diet (wet food is 70-80% water), so they may drink very little from the bowl.

The clinical threshold for concern is when a cat drinks more than 100 mL per kg per day — that's more than double the normal amount. For a 4 kg cat, that would mean drinking more than 400 mL (about 1.7 cups) of water per day. But you don't need to measure precisely to know something is wrong. Trust your instincts: if you've noticed a clear change in your cat's drinking habits, it's worth investigating.

Here are some practical ways to tell if your cat is drinking more: the water bowl needs refilling much more frequently, you see your cat at the water bowl multiple times throughout the day (not just after eating or playing), litter box clumps are larger than usual or you're finding more urine than solid waste, and you may notice your cat seeking out unusual water sources like dripping faucets, toilets, or puddles.

Other Causes of Increased Thirst

While CKD is the most common cause of increased thirst in older cats, it's not the only one. Your vet will need to rule out other conditions:

Diabetes mellitus causes high blood sugar, which leads to sugar in the urine. The sugar draws water with it, causing excessive urination and thirst. Diabetic cats often also lose weight despite eating more, and may have sweet-smelling breath. A simple blood glucose test and urinalysis can diagnose diabetes.

Hyperthyroidism (overactive thyroid) is common in older cats and causes increased metabolism. Cats eat more but lose weight, are hyperactive, and may drink more. A blood test for thyroid hormone (T4) is diagnostic. Hyperthyroidism and CKD can coexist, and treating one can sometimes unmask the other, so your vet will likely test for both.

Urinary tract infection can cause increased urination (though usually in smaller amounts each time). A urinalysis and culture will identify infection.

Pyometra (uterine infection in unspayed females) is a medical emergency that can cause increased thirst. If your unspayed female cat is drinking excessively, lethargic, and has a swollen abdomen, seek emergency care immediately.

Medication side effects — certain drugs, including corticosteroids and diuretics, can increase thirst and urination.

What to Tell Your Vet

When you call your vet, being specific helps them prioritize tests and get to a diagnosis faster. Here's what to mention: when you first noticed the change in drinking, approximately how much water your cat drinks per day now (if you can estimate), whether you've noticed changes in the litter box (larger clumps, more frequent urination, accidents outside the box), any other symptoms you've observed (weight loss, appetite changes, vomiting, lethargy, changes in coat quality), your cat's diet (dry vs wet food), and any medications your cat is currently taking.

What Tests Your Vet Will Run

Expect a thorough workup. Bloodwork will include a complete blood count (CBC) and chemistry panel, which checks creatinine, BUN, phosphorus, and other values. Many vets now also include SDMA, which can detect kidney issues earlier than creatinine — read more about what these lab values mean. A urinalysis checks urine concentration (specific gravity), protein levels, and signs of infection. Your vet may also check blood pressure (CKD cats are prone to hypertension) and thyroid levels (T4).

If It Is CKD: Early Intervention Matters

If the diagnosis is CKD, early detection is genuinely good news — because it means you have the most options. Cats diagnosed at IRIS Stage 2 can often live for years with dietary management alone. At Stage 3, you may need to add subcutaneous fluids and medications, but quality of life can still be excellent (our home SQ fluid guide walks you through this). The key interventions at every stage are proper hydration, a renal-appropriate diet (see our renal diet comparison), regular bloodwork monitoring, and addressing complications like high blood pressure, proteinuria, and elevated phosphorus.

Encouraging Hydration While You Wait

Regardless of the cause, keeping your cat hydrated is important while you wait for your vet appointment. Try these strategies: switch from dry to wet food (or add warm water to dry food), invest in a pet water fountain (many cats prefer moving water), place multiple water bowls throughout the house in quiet locations, use wide, shallow bowls (cats dislike their whiskers touching the sides), and keep water fresh — change it daily. Never force your cat to drink by squirting water into their mouth, as this can cause aspiration.