Thankfully, diabetes insipidus in dogs is uncommon. It’s a condition which causes dogs to drink excessively, and to produce large volumes of very dilute urine. This is also known as ‘water diabetes’, which is not the same as ‘sugar diabetes’ (diabetes mellitus). So if you are wondering why is my dog extremely thirsty and thinking it might be diabetes insipidus, it is important to know that there are many other more common health conditions which cause similar symptoms. Your vet will want to rule these out first, so reaching a diagnosis can take time. While diabetes insipidus cannot be cured, it can often be successfully managed.

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What is diabetes insipidus in dogs?

The kidneys have many important jobs. One of these jobs is to maintain water balance in the body, by filtering the blood and retaining or excreting appropriate amounts of water as needed. Water balance is controlled by a hormone called antidiuretic hormone (ADH), which is also known as vasopressin. 

Diabetes insipidus affects the ability of the kidneys to concentrate urine. This means that instead of conserving water in the body, too much is passed out as urine. This makes the dog drink excessively, to try to compensate for the large volumes of water loss in the urine. 

There are two types of diabetes insipidus:

Central diabetes insipidus: 

Antidiuretic hormone (ADH) is made and stored in the brain. It is produced in a part of the brain called the hypothalamus and is then transported to another area in the brain, called the posterior pituitary gland. Here it is stored, and released into the circulation as needed. 

Central diabetes insipidus occurs when this pathway is no longer working, so not enough (or no) ADH is released into the bloodstream.

Nephrogenic diabetes insipidus: 

This is where the kidneys are resistant to ADH, so they don’t respond to the hormone, and so fail to conserve water in the body. This form is the most common.

Thankfully, both forms of diabetes insipidus in dogs are rare.

How does a dog get diabetes insipidus?

Nephrogenic diabetes insipidus can occur as a primary condition, such as a congenital issue, or it can be idiopathic. More often, it occurs secondary to another condition, such as:

  • Kidney disease
  • Liver disease
  • Some medications 
  • Cushing’s disease
  • Pyometra 
  • Hypercalcaemia (high blood calcium levels)
  • Hypokalaemia (low blood potassium levels)
  • Addison’s disease.

The symptoms of diabetes insipidus are largely the same, regardless of the underlying cause.

How do you know if your dog has diabetes insipidus?

The main symptom of diabetes insipidus is extremely excessive thirst and urination (weeing). This is medically termed polyuria (increased urination) and polydipsia (increased thirst), or PUPD. Dogs may need to urinate so often that they actually become incontinent. 

PUPD is often the only symptom of diabetes insipidus. However, you may also see a reduced appetite and weight loss. Other symptoms could be present, depending on the underlying type and cause. For example, if there is a mass in the brain, you may also see signs such as blindness, an unsteady gait, walking in circles, or seizures.

Why is my dog is extremely thirsty – could they have diabetes insipidus?

There are many other, more common causes of PUPD in dogs. So, if your dog is extremely thirsty, drinking and weeing excessively, diabetes insipidus is possible, but less likely. 

So, what other diseases make dogs thirsty? Some other causes of PUPD in dogs include:

  • Diabetes mellitus (sugar diabetes)
  • Kidney disease
  • Liver disease
  • Pyometra (uterus infection)
  • Hypercalcaemia (high blood calcium)
  • Electrolyte disturbances
  • Hyperadrenocorticism (Cushing’s disease)
  • Hypoadrenocorticism (Addison’s disease)
  • Psychogenic polydipsia.

Because diabetes insipidus is rare in dogs, your vet will want to rule out more common conditions first. 

How is diabetes insipidus in dogs diagnosed?

Your vet would start by running some routine urine and blood tests, to rule out some of the other (more common) conditions. In diabetes insipidus, the urine will be very dilute, almost like water. There may be signs of dehydration and electrolyte imbalance on the blood tests.

If your vet suspects diabetes insipidus, there are two tests they may wish to perform, after ruling out other causes of PUPD:

Water deprivation test

This test is used to find out whether a dog is able to release ADH when they are dehydrated. It involves hospitalising the dog and withholding water for a period of time. During this time, the vet measures the dog’s weight, the amount of urine they produce, and the concentration of their urine. When deprived of water a healthy dog would start to release ADH, meaning they would produce concentrated urine, so conserving water in the body and staying adequately hydrated. Dogs with diabetes insipidus cannot concentrate their urine and will become dehydrated.

Due to the nature of this test, it can be dangerous. It should only ever be performed on an animal that has been admitted to a veterinary hospital for constant monitoring. If the vet detects signs of dehydration, the test would be stopped, and your dog would be treated with fluid therapy. 

You should never withhold water from your pet at home – this can be life-threatening. 

Anti-diuretic hormone test

This test is used to distinguish between central and nephrogenic diabetes insipidus, so is usually performed after a water deprivation test has confirmed diabetes insipidus. 

The vet would administer a synthetic ADH hormone (vasopressin). Dogs with nephrogenic diabetes insipidus are not able to respond to the ADH, so the urine stays very dilute. Dogs with central diabetes insipidus aren’t producing their own ADH, but can still respond to ADH, so the dog’s urine will become concentrated.

How to treat a dog with diabetes insipidus

Unfortunately, there is no cure for diabetes insipidus. However, it can often be managed with treatment. The aim of treatment is to reduce the symptoms, including the excessive thirst and urination, and to maintain hydration. If an underlying cause is found, this will also need to be treated.

Since dogs with central diabetes insipidus fail to produce enough ADH, it is treated using a synthetic form of ADH called desmopressin. Desmopressin is available in several forms, which are given in different ways- either as an eye drop, by mouth, or injected under the skin. 

Some dogs with nephrogenic diabetes insipidus may also show some improvement on desmopressin. If not, nephrogenic diabetes insipidus may be treated using chlorothiazide diuretics and a low salt diet. These help by increasing the amount of water the kidneys re-absorb, so the amount of urine produced decreases.

Dogs should be allowed free access to fresh water at all times.

What is the prognosis for dogs with diabetes insipidus?

Diabetes insipidus cannot be cured, but can usually be successfully managed for a period of time. However, the prognosis greatly depends on the underlying cause. For example, if the diabetes insipidus is caused by a brain tumour, the prognosis will depend on the type of tumour, where it is and how quickly it grows and/or spreads (metastasises). 

Key points

Diabetes insipidus in dogs is a rare condition, which causes excessive drinking and weeing. There may be other symptoms, depending on the underlying cause. There are many other, more common, causes of increased drinking and weeing in dogs. 

Antidiuretic hormone (ADH) is a hormone responsible for maintaining water balance in the body. There are two types of diabetes insipidus in dogs: central (where the dog does not produce enough ADH) and nephrogenic (where the dog cannot respond to ADH). 

Diabetes insipidus cannot be cured, but can often be successfully managed with treatment. The long-term prognosis will depend on the underlying cause.