How much should dogs drink?

Why do dogs get thirsty?

The drive to drink is controlled largely by the concentration of the blood. If the concentration becomes too high (as in dehydration), they start to feel thirsty. This is usually (although not always) as a result of increased fluid loss, meaning that the dog must drink more to compensate.

So, what can cause increased thirst?

There are a wide range of common conditions that can make a dog more thirsty than usual. They include:

• Simple dehydration. This is by far the most likely reason; causes include:
  ○ Not having drunk enough (!).
  ○ Fluid loss due to vomiting or diarrhoea.
  ○ Overheating.
• Fever. A raised temperature due to an infection will make dogs more thirsty; in addition, they lose water and tend to become dehydrated.
• Kidney disease. A dog’s kidneys work to maintain their fluid balance. If the dog is dehydrated, they reduce water loss, whereas if they are overhydrated, the kidneys increase water loss. If the kidneys are damaged (by infection, toxins, or chronic renal failure), they progressively lose this capacity. This results in progressive inability to concentrate their urine, increasing fluid loss.
• Certain drugs such as steroids, alter the way the kidneys process water, increasing urination and also driving increased thirst.
• Cushing’s Disease. This hormonal condition means that the dog’s body produces excessive quantities of natural steroids – with the same result as the artificial kind.
• Pyometra. A womb infection in a bitch often presents initially with increased thirst. It generally progresses to lethargy, vomiting, septicaemia and is usually fatal without treatment.
• Diabetes mellitus (sugar diabetes). This is very common in dogs, and occurs when the dog cannot regulate their blood sugar levels. As their blood sugar level increases, it eventually exceeds the level that the kidneys can reabsorb, resulting in glucose in the urine. This leads to increased urination, dehydration and increased thirst.
• Diabetes insipidus (water diabetes). This is a rarer cause of increased urination, and is a different type of diabetes. Sugar diabetes results from failure of the hormone insulin, whereas water diabetes occurs if the dog is unable to produce the hormone vasopressin (ADH). Insufficient vasopressin levels result in excessive urination.
• Psychogenic Polydipsia. This is a behavioural disorder that isn’t well understood. Essentially, the dog is drinking too much just because they like to drink! Fortunately, it isn’t harmful, but can only be diagnosed by ruling out all other possible causes.

So how much SHOULD my dog be drinking?

Most dogs drink about 50ml per kg body weight, including water in their food. We wouldn’t normally worry, however, until they were drinking 90ml per kg, or if their thirst suddenly increases.

If you’re concerned that your dog’s drinking too much, make an appointment to get them checked out by one of our vets – the earlier any problem can be diagnosed, the better the outcome is likely to be.