While there may be a simple explanation for your cat’s apparent increased thirst (such as hot weather!), it should not be ignored. A true increased thirst (known as polydipsia) may be a symptom of an underlying problem.
First let’s consider some simple reasons why your cat may be drinking more than usual.
A change of food
Moving from wet to dry food will cause an increase in thirst. Dry food may slow dental disease progression, particularly specially-formulated dental diets; however, if your cat has a history of urinary or renal issues, discussed more later, wet food is ideal for encouraging water intake. Cats are notoriously fussy about their drinking habits and are often guilty of not drinking enough, leading to long-term health issues. Changing to a higher salt or low protein diet may also increase thirst.
Especially if it’s a prolonged rain-free spell which means ‘natural’ water sources such as puddles dry up. Cats are forced to come indoors for water and may appear to be drinking more. Encourage water intake by avoiding plastic bowls and use large bowls filled high to give that natural effect. Multi-cat houses should have several water sources so they are not forced to share. Some cats like running water so a water fountain may help. All cats have unique tastes so try and figure out what, when, and how your cat likes to drink and tailor your provisions to their needs.
For example, diuretics, steroids and some anti-seizure drugs may cause increased thirst. In addition, increased thirst is often a sign of potentially dangerous side-effects from some painkillers. If your pet is on any medication and has started drinking more ask your vet if the two could be linked.
This may be temporary, after a mad moment can cause thirst just like with us after exercise. Alternatively, fevers may also cause a cat to drink more but they are usually showing other signs of illness too.
Diarrhoea (or vomiting)
The conditions cause fluid loss. Cats will increase their intake to compensate. If severe or lasting longer than 24 hours you should always contact your vet.
What diseases could cause increased thirst?
If persistent and not easily explained there may be more to it. Most cases of polydipsia actually occur in response to fluid loss through excessive urination (polyuria). “Psychogenic polydipsia”, a compulsive drinking disorder, is the main cause of true polydipsia and it is very rare and poorly understood in cats.
The main causes of this responsive thirst are discussed below.
Chronic kidney disease (CKD)
Common in ageing cats, around 20-50% of cats over 15 years old have some degree of CKD. It’s seen three times more frequently in cats than dogs. Cats begin to lose the ability to concentrate their urine with CKD, drinking more to compensate for this. Other signs may be a poor coat, vomiting, bad breath, weakness and a poor appetite. Blood and urine tests diagnose the condition which is progressive and irreversible. Treatment aims to conserve current function and manage the condition, by means of dietary change, increased water intake, and medication to control symptoms.
Patients can suffer lethargy, loss of appetite, weight loss, a swollen tummy, yellow gums/skin (jaundice) as well as increased thirst. Blood tests help confirm liver disease but there are many differing causes. Specific tests like biopsies can be offered to allow more specific diagnosis, leading to specific treatment options. If this is not possible, symptomatic treatments may be given alone.
AKA ‘sugar diabetes’, this occurs due to a lack of insulin, or an abnormal response to it. Insulin helps move glucose from the bloodstream into cells where it’s used for energy. Without insulin, glucose builds up in the bloodstream and then the urine. Water is drawn into the urine following the glucose (a process called osmosis) and urination increases. In an effort to replace the lost water, thirst increases. Increased appetite and weight loss are other symptoms. Diagnosis is via blood and urine tests. Treatment involves giving insulin and usually a diet change. Overweight cats are at higher risk of becoming diabetic and are more unstable if they are diabetic, another good reason to keep your cat a healthy weight.
Caused by an overactive thyroid gland and is common in older cats. As well as an increased thirst, cats may have an increased appetite, increased activity, an unkempt coat and weight loss. The signs arouse suspicions which are confirmed using blood tests. Treatments include long-term medication, surgical removal of diseased tissue, or less commonly, radioactive iodine treatment.
Urinary tract disease
For example cystitis; this can cause increased urination, but can cause increased thirst as well.
A womb infection, this can occur in un-neutered female cats and may cause thirst. Other signs such as fever, lack of appetite, vomiting and a vulval discharge may also appear. Neutering your cat prevents this and many other conditions.
Other rare reasons
Including high calcium levels, the cause of which in cats is often unknown; hyperadrenocorticism (Cushing’s disease), a hormonal disease that is very rare in cats arising from an excess of the hormone cortisol; and central diabetes insipidus, a very rare condition caused by a lack of the hormone ADH (antidiuretic hormone) that controls how much water the kidneys need to conserve.
What can I do?
In a one-cat household you could monitor their water intake. Fill their water bowl to the brim and measure the amount of water left over at the end of the 24-hour period. Take this away from the volume of water in the full water dish. Polydipsia is defined in cats as drinking more than 100 ml/kg bodyweight per day, but any cat that you think is drinking more than usual should be seen by a vet. Let the vet know the amount your cat is drinking if measured, and consider taking a urine sample along with you. Ask your vet for advice on how to get one.
Your vet will take a history and perform an examination looking for hints as to why your cat is so thirsty. There is often no obvious cause so blood and urine tests are often advised. Once a cause is found a suitable treatment can begin.