- Reference Number: HEY-946/2023
- Departments: Diabetes & Endocrinology
- Last Updated: 1 September 2023
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What is a water deprivation test?
You have probably been troubled by symptoms of increased thirst and/or passing a lot of urine. Following discussion with your doctor, he has advised that you have this test. The purpose of this test is to find out if you are producing enough of a hormone called anti-diuretic hormone (ADH), from a small gland called the pituitary gland.
Why do I need a water deprivation test?
You doctor recommended this test to see whether you might have a condition called diabetes insipidus and to investigate the cause of your symptoms. ‘Diabetes insipidus’ is a rare condition caused either by deficiency of ADH or the kidneys’ inability to respond to this hormone.
Can there be any complications or risks?
There is a risk of dehydration but the nursing staff will monitor you throughout the test and liaise with medical staff as required.
What are the alternatives to the test?
There is no alternative to this test to find out the cause of your symptoms of excessive thirst or passing a lot of urine. It is important to know whether you have diabetes insipidus and, if you do, whether the condition is due to a pituitary problem or a kidney problem. The information will allow you and your doctor to manage your condition.
How do I prepare for the test?
Please read the information leaflet. Share the information it contains with your partner and family (if you wish) so that they can be of help and support. There may be information they need to know, especially if they are taking care of you following this test.
If you are taking medication such as DDAVP (Desmopressin) or if you are taking water tablets such as bendroflumethazide, furosemide, spironolactone, eplerenone or chlorthalidone. This is not an exhaustive list. Your doctor will have reviewed your medication list before ordering the test. The water tablets should be discontinued the evening before the test after discussion with your doctor. You may eat and drink and take your usual medication on the morning before you come for the test. Please bring all of your medication with you. You may have a light breakfast before 06:30am and clear fluids (such as water, dilute juice) until 08:00am on the morning of the test but no coffee, tea, alcohol or tobacco for 24 hours before this test.
What will happen?
You need to attend the Medical Day Unit on the day of your test at 08:00am. Your weight will be recorded and urine and blood samples will be collected at periodic intervals throughout the day and sent to the Biochemistry Department for analysis. You will not be allowed to drink during the test but dry foods are allowed. It is very important that you do not drink anything during the test, even if you feel thirsty, as this makes it very hard for us to interpret the results. Smoking is not allowed during the test as this will affect the results. At 4:30pm, an injection of anti-diuretic hormone is administered. You will then be allowed to drink but you are required to remain in the unit for further urine and blood samples to be taken. The test should end at 6:30pm.
What happens afterwards?
You should be able to undertake normal activities after the test is finished and you will be allowed to drive home. The results of the blood and urine samples are analysed and will be discussed with you in the clinic at your next appointment. If the results show that you require treatment with anti-diuretic hormone, you will receive a call within a few days of the results being available about starting the treatment.
It is important that you do not drink too much that evening and night after receiving the injection. The injection causes concentration of urine and if you drink excessively, you may develop an imbalance in the salt levels in your blood. This may lead to feeling ill and disorientated. We advise that you do not drink more than 1 litre (about 2 pints) of fluids after the test until midnight to prevent this. You may drink your choice of fluids.
Should you require further advice on the issues contained in this leaflet, please do not hesitate to contact the Endocrine Specialist Nurse on: (01482) 675360
Patient self-help groups and further information: The Pituitary Foundation, PO Box 1944, Bristol BS99 2UB, www.pituitary.org.uk Telephone number: 0845 450 0376