See your GP if you think you may have diabetes insipidus. They will ask you about your symptoms and will carry out several tests. Your GP may refer you to an endocrinologist (a specialist in hormone conditions) for these tests.
As symptoms such as producing lots of urine can be linked to other conditions, including diabetes mellitus, tests are needed to confirm or rule out a diagnosis of diabetes insipidus. The tests can also identify which of the two types of diabetes insipidus you have: cranial diabetes insipidus or nephrogenic diabetes insipidus.
The tests you may have to confirm a diagnosis of diabetes insipidus are described below.
Water deprivation test
If you have a water deprivation test, you will not be allowed to drink 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 water deprivation test, your GP or endocrinologist will take urine samples to measure the amount of urine you are producing. They may also carry out 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, if there is a high amount of sugar in your urine, you may have diabetes mellitus, not diabetes insipidus.
Antidiuretic hormone (ADH) test
After the water deprivation test, your GP or endocrinologist will give you a small dose of ADH, usually as an injection. This will show how your body reacts to the hormone and can help identify which type of diabetes insipidus you have.
If the dose of ADH causes you to stop 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 lots of urine despite the dose of ADH, it suggests that there is already enough ADH in your body, but that 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 will need to be treated before you can receive treatment for diabetes insipidus.
