Are they always seeking out puddles, bowls, even cups?
If so, there’s a good chance they’re suffering from polydipsia – excessive thirst, defined as drinking over 45ml per kg bodyweight per day.
If so there are 5 common causes that you need to know about…
1) Fever and Infection
Cats can suffer from a wide range of infections – and it’s often hard to work out what’s going on! However, most infections, plus some other conditions such as tumours, cause a fever, a raised body temperature. This is actually a good thing, as it increases their immune system’s ability to fight the bugs; however, it also makes them feel thirsty.
A cat with a fever is often miserable, grumpy, and will try and hide away somewhere warm and cosy; often they are obviously ill or in pain as well.
2) Kidney Failure
Cats, just like us, have 2 kidneys; and like us, they can develop kidney failure. However, this is very, very common in cats – in fact, some vets even think that all cats who live long enough will eventually develop kidney failure. This is because cats are obligate carnivores (they have to eat meat), so their kidneys have to work extra-hard to filter out the waste products from their diet.
The kidneys don’t just filter out waste, they also control the amount of water in the cat’s body. When they start to fail, the cat produces progressively more dilute urine (polyuria), so they have to drink more to maintain their hydration levels (termed secondary polydipsia).
Other symptoms include weight loss, loss of appetite, bad breath, and (in severe cases) vomiting and seizures. Kidney failure is more common in older cats, although it can affect them at any age, and some cats have a genetic disease that predisposes them to early renal failure (polycystic kidney disease).
3) Diabetes mellitus
In diabetes, cats are unable to control their blood sugar levels; as a result, their blood sugar becomes abnormally raised. Eventually, glucose levels in their bloodstream become so high that the kidneys can’t reabsorb it all. However, with this extra sugar in the urine, the kidneys lose excessive water, leading to polyuria and then secondary polydipsia. In fact, the urine may contain so much sugar it actually smells sweet (“mellitus” comes from the Latin word for “honey”!).
Diabetes can affect any cat, at any age; and other symptoms include weight loss, increased appetite, a predisposition to urinary infections, sometimes a strange smell on the breath (like pear drops), and eventually collapse, dehydration, coma and death if untreated.
The thyroid glands in the neck of a cat produce a hormone called thyroxine that regulates their basic metabolic rate. If the thyroid glands become overactive (as in hyperthyroidism), they produce more thyroxine, leading to a higher metabolism – so cats lose weight, are ravenously hungry, have a dangerously high heart rate and blood pressure, and are often “manic” or “kittenish”. Another, less well known, effect of hyperthyroidism is increased filtration by the kidneys (due to the high blood pressure). This may lead to dehydration, and secondary polydipsia to compensate.
Hyperthyroidism is most common in older cats, and is usually due to a tumour on one of the thyroid glands.
There are a wide range of possible causes of dehydration in cats, other than the ones listed above. Probably the most important are…
Dry or salty food, especially if they have limited access to water. Many cats don’t drink regularly at all – if they’re eating wet food, that’s fine, they are desert animals originally, so don’t need a lot. However, if their diet changes suddenly to eating very dry, or very salty, food, they may need to drink more to prevent dehydration. If you change it slowly, on the other hand, they’ll have plenty of time to adapt.
Overheating – cats love warm places, but they’re usually pretty good at moving if it gets too hot for them! However, if they can’t escape (for example, they’re shut in an airing cupboard, or a hot car), they will lose water in an attempt to cool down. The dehydration may cause kidney failure, organ damage, or even death; but even if not, they’ll need to drink to top up their fluid levels.
Blood loss, from any source, is potentially fatal if severe enough. However, assuming the ruptured vessels clot in time (and cats are very good at this!), the cat drinks, replacing fluid, to maintain their blood pressure.
If your cat is drinking excessively, make an appointment to see one of our vets as soon as possible. Most of these conditions are manageable, but the earlier they are picked up, the better your cat’s prognosis!