Does your dog or cat drink a lot of water? A visit to the vet might be in order, as excessive thirst can signify underlying health problems.

"Being excessively thirsty and drinking too much water are relatively common problems for dogs and cats. This can be due to a range of causes, from hormonal imbalances to organ problems and even behavioural issues," says veterinarian David Gething, of Creature Comforts www.creaturecomforts.com.hk.

In general, a dog or cat drinks about 20ml to 40ml of water per kilogram of its body weight every day, according to Gething. For example, if a cat weighs 5kg, it would be normal for it to drink between 100ml and 200ml of water per day, or if a dog weighs 25kg, it should drink between 500ml and a litre of water per day, depending on activity levels and diet.

Gething says pets that drink more than 100ml of water per kilogram of their body weight are consuming too much, and the cause needs to be addressed.

"Dogs and cats that drink excessive amounts of water also generally pass large amounts of urine, and this is often one of the signs owners will first notice. A dog may be desperate to go outside all of the time, or may even pass urine indoors when they can't hold on. A cat's litter tray may need to be cleaned and emptied far more often, and, in some cases, the tray may overflow."

Of hormonal imbalances, Gething says: "The most common hormones that can affect drinking and urinating are insulin and cortisol. Diabetes is the result of imbalances in the insulin system, and can be due to poor lifestyle and diet, or in some cases due to lack of production in the pancreas."

Cortisol can cause problems when levels are high (Cushing's disease) or low (Addison's disease), and in both cases will result in excessive thirst and urination.

"In many cases, apart from being excessively thirsty and urinating more, pets with hormonal issues can be happy, have a good appetite and be seemingly normal, but the increase in thirst and drinking is often very obvious and pronounced."

Hormonal issues are treatable, allowing pets to return to a full, healthy and happy life. However, Gething says, diabetes, Cushing's disease or Addison's disease can all become serious if they go untreated - to the point of being life-threatening - and pets showing symptoms should be tested.

Organ problems, particularly issues with kidney or liver function, are especially common in cats that are drinking and urinating excessively, the vet says.

"Reduced kidney or liver function is more common in older pets, and signs can develop slowly over time as the disease progresses."

In addition to the symptoms of increased thirst and urination, pets with kidney or liver problems will often show weight loss, become picky eaters, lethargic and, in some cases, vomit.

According to the vet, kidney and liver problems are treatable in many cases and, although they are sometimes not curable, treatment will still greatly improve the quality and length of a pet's life.

In some cases, behavioural or emotional issues can affect a pet's water intake.

"Although it sounds odd, drinking is one of the only things that most pets control," Gething explains. "Our dogs and cats usually can't control when they are fed or walked, when their owners come home, or when they have playtime. But they can control when they drink. For this reason, pets will sometimes focus excessively on drinking, and over time develop a compulsive disorder."

He adds that this issue is particularly common in Hong Kong. "I suspect this is partly due to dogs and cats spending more time alone indoors, with little else to keep them occupied and stimulated during the day."

Behavioural causes are much more common in dogs than cats, and can be difficult to diagnose and treat.

"Your vet will generally rule out all other hormonal and organ-related causes first, and then make the presumptive diagnosis of behavioural issues," Gething says.

Treatment often involves modifying a pet's environment, increasing its activities and providing more mental stimulation, although in some cases medication is also required.

"If you do suspect your dog or cat is drinking too much, then I recommend seeing your vet soon. Many causes are fairly easily treated, but if left unattended can become quite significant," Gething says. 

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