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 type 1 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'd 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.
After the water deprivation test, you may be given a small dose of AVP, usually as an injection. This will show how your body reacts to the hormone, which helps to identify the type of diabetes insipidus you have.
If the dose of AVP stops you producing urine, it's likely your condition is due to a shortage of AVP. If this is the case, you may be diagnosed with cranial diabetes insipidus.
If you continue to produce urine despite the dose of AVP, this suggests there's already enough AVP in your body, but your kidneys aren't responding to it. In this case, you may be diagnosed with nephrogenic diabetes insipidus.
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, it may need to be treated too, along with treatment for diabetes insipidus.