See your GP if you think you have diabetes insipidus. They will ask about your symptoms and carry out several tests. Your GP may refer you to a a specialist in hormone conditions (endocrinologist) for these tests.
As the symptoms are similar to those of other conditions, including type 1 or type 2 diabetes, tests are needed to confirm or rule out diabetes insipidus.
The tests can also identify which type of diabetes insipidus you have: cranial diabetes insipidus or nephrogenic diabetes insipidus.
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 will 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 are producing is 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 blood sugar (glucose), calcium and potassium. If you have diabetes insipidus, your urine will be very diluted, with low levels of other substances. However, a high amount of sugar in your urine may be a sign of type 1 or type 2 diabetes, not 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 shows how your body reacts to the hormone which helps identify the type of diabetes insipidus you have.
If the dose of ADH stops you producing urine, it is likely your condition is due to a shortage of ADH. If this is the case, you may be diagnosed with cranial diabetes insipidus.
However, if you continue to produce urine despite the dose of ADH, it suggests there is already enough ADH in your body, but your kidneys are not responding to it. In this case, you may be diagnosed with nephrogenic diabetes insipidus.
MRI scan
Magnetic resonance imaging (MRI) is a scan that uses a strong magnetic field and radio waves to produce images of the inside of your body, including your brain.
You may need an MRI scan if your GP or 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.
