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Thirsty Cats - When To Worry

Thirsty Cats - When To Worry
by Dr Grant Hampson

Read time: 3 min

Cats have a very interesting relationship with water. We'll buy them specific water bowls for them to slurp to their heart's content, only for them to exclusively drink from a running tap, or worse - shove their furry faces into your water glass. We guess some things just taste better when they're not yours?

You might have noticed that your cat has suddenly started drinking a lot more water than they used to, so we're here to help you work out if it's a symptom of a wider problem, or if they are just particularly parched.

My cat is drinking more, should I be worried?

If your cat starts drinking and urinating more than usual, this can be a sign of disease, particularly in older cats. The medical term for drinking more is polydipsia and for urinating more it is polyuria, you may hear the term PU/PD when your vet discusses this with you.

How much should my cat be drinking?

A healthy cat can consume between 20 and 90mls per kg of body weight each day. This volume includes moisture that they are getting from their food. Cats on wet food will be getting more moisture from their diet so may drink “less” when compared to a cat who is on a dry diet.

How much is too much?

Polydipsia is defined when your cat starts to drink over 100ml per kg of body weight within a 24 hours period. When your cat starts to drink more they will also urinate more, which you may or may not notice depending on your cats habits.

You can measure your cats water intake by measuring how much water you put down in the morning and measuring it 24 hours later. This is more challenging in a household with more than one cat.

So, why is my cat drinking more than usual?

Drinking excessively is often associated with disease that is causing the kidneys to produce dilute urine. Your cat's body recognises this increased loss of fluid, and your cat drinks more to compensate.

Polyuria is often triggered by diseases that primarily affect the kidneys, or a secondary disease that has a knock on effect on kidney function. The most common diseases that are associated with PU/PD are:

  • Chronic Kidney Disease (CKD): The main job of the kidneys is to balance the fluid within the body and remove toxins from the blood, like a giant filter. In CKD the cells inside this filter prevent it from working effectively. As the filtering function of your cats kidneys continues to worsen, they lose the ability to concentrate urine. This results in your cat urinating more frequently and they compensate by drinking lots more.

  • Diabetes: Diabetes mellitus results in excess levels of glucose (sugar) in the blood. Normally the kidneys reabsorb this glucose back into the bloodstream. However in diabetes, there is too much glucose to reabsorb and it ends up spilling into the urine. As all this glucose spills over, it pulls water with it, resulting in high volume urine production.

  • Hyperthyroidism: The thyroid glands are two small organs found under the skin in the neck. Thyroid hormone is produced here and is heavily involved in a cats metabolism. Your cat’s body works hard regulating their hormones but in some cases the thyroid gland can become overactive, producing too much of the thyroid hormone. When this happens your kidneys start to work harder, and their filtration rate increases, producing more urine. There is also a thought that hyperthyroidism triggers the thirst centers of the brain, causing them to drink more, this is known as primary polydipsia.

Illustration of a cat's thyroid showing a normal and an enlarged thyroid gland
  • Other diseases: Increased calcium, kidney infections, liver diseases and more.

So what next?

If you are concerned that your cat is drinking or urinating more, it is really important that you arrange a consultation with a vet. They are likely to do a blood test to investigate all the possible causes discussed above. They may also require a urine sample. If you can get a urine sample before you go these might be useful for the vet.

To get a urine sample, you can either purchase non-absorbable cat litter from your vet or online. The first urine sample of the day provides the most accurate results, and try to get the sample to your vet within a couple of hours.

Once your vet has these results they can direct you on what to do next.


Depending on the diagnosis there will be options for treatment going forwards. The most important thing to take home is, as cats get older they may be more prone to disease, and a symptom may be drinking and urinating more frequently. So pay attention to your cats drinking habits and if worried, chat to your vet.

If you have any further questions about why your cat is drinking more, please reach out to us at

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