Diabetes insipidus - Diagnosing diabetes insipidus

See your GP if you have the symptoms of diabetes insipidus. They'll ask about your symptoms and carry out a number of tests.

You may be referred to an endocrinologist (a specialist in hormone conditions) for these tests.

As the symptoms of diabetes insipidus are similar to those of other conditions, including type1 diabetes and type 2 diabetes, tests will be needed to confirm which condition you have.

If diabetes insipidus is diagnosed, the tests will also be able to identify the type you have – cranial or nephrogenic.

Water deprivation test

A water deprivation test involves not drinking any liquid for several hours to see how your body responds. If you have diabetes insipidus, you'll continue to pass large amounts of dilute urine, when normally you would only pass a small amount of concentrated urine.

During the test, the amount of urine you produce will be measured. You may also need a blood test to assess the levels of antidiuretic hormone (ADH) in your blood.

Your blood and urine may also be tested for substances such as glucose (blood sugar), calcium and potassium. If you have diabetes insipidus, your urine will be very dilute, with low levels of other substances. A large amount of sugar in your urine may be a sign of type 1 or type 2 diabetes rather than diabetes insipidus.

Antidiuretic hormone (ADH) test

After the water deprivation test, you may be given a small dose of ADH, usually as an injection. This will show how your body reacts to the hormone, which will help identify the type of diabetes insipidus you have.

If the dose of ADH stops you producing urine, it's likely your condition is due to a shortage of ADH. If this is the case, you may be diagnosed with cranial diabetes insipidus.

However, continuing to produce urine despite the dose of ADH suggests that there's already enough ADH in your body, but your kidneys aren't responding to it. In this case, you may be diagnosed with nephrogenic diabetes insipidus.

MRI scan

Magnetic resonance imaging (MRI) is a type of scan that uses a strong magnetic field and radio waves to produce images of the inside of the body, including your brain.

You may need an MRI scan if your endocrinologist thinks you have cranial diabetes insipidus as a result of damage to your hypothalamus or pituitary gland.

If your condition is due to an abnormality in your hypothalamus or pituitary gland, such as a tumour, it may need to be treated before you can receive treatment for diabetes insipidus.

Dehydrated: Dehydration is an excessive loss of fluids and minerals from the body.
Glucose: Glucose (or dextrose) is a type of sugar that is used by the body to produce energy.
Kidneys: Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
MRI: MRI stands for magnetic resonance imaging. It is the use of magnets and radio waves to take detailed pictures of inside the body.
Pituitary gland: The pituitary gland is a pea-sized gland in the centre of the head, which hangs below the brain and produces hormones.
Urinalysis: Urinalysis/UA is when a urine sample is tested, commonly to check for any signs of infection or protein or sugar levels.