If you want to determine how much water your cat is drinking, allow her only one source of water.
(Q) My four-year-old cat has always drunk lots of water, even as a kitten. Recently though she seems to be drinking even more. She does mainly eat dry food, but I'm sure she's drinking an excessive amount. Should I get her checked out?
(A) Vet Elsie Robertson says: Excessive drinking, also known as polydipsia, usually leads to excessive urination (or polyuria). Polydipsia and polyuria can be early indicators of a variety of diseases including kidney disease, diabetes mellitus, hyperactivity of the thyroid gland and liver disease.
To establish whether she is truly polydipsic, I would advise for you to measure how much water your cat is drinking daily over a week, although this can be difficult with an outdoor cat. This information can be recorded in a diary and taken to your vet.
Some cats may begin drinking from a dripping tap in the sink or from an open toilet bowl. If you want to determine how much water your cat is drinking, allow her only one source of water (easier if she's an indoor cat) and subtract the amount left in the bowl after 24 hours from the amount you put in originally. This includes any water that is taken in when eating canned food. Any more than 60ml per day should prompt you to contact your vet. He or she will be able to perform a full physical examination and also assess her urine to determine whether her kidneys are doing their job and actively concentrating the urine.