Water Deprivation Test

Why am I having this test?

• Your doctor has requested that you undergo this test to try to establish a cause for your excessive thirst, drinking or passing urine.
• To see whether you have a condition called Diabetes Insipidus. This is not the same as the more common condition – Diabetes Mellitus.

Who carries out this test?

A nurse who specialises in endocrinology is responsible for carrying out this test.

Where is the test carried out?

• You will be sent a letter with details of the test and which department you will need to attend.
• If you wish you may bring a companion with you. They may stay with you during the test.

How long will the test take?

• Please allow 10 hours for this test, although timings will vary from patient to patient.
• You may wish to bring a book/magazine/activity with you.

What do I need to do before the test?

• Do not drink tea or coffee on the morning of the test as this may interfere with the results.
• On the morning of the test you may drink water or squash until you arrive in the department.
• You may have an early light breakfast before 7.00am of toast or cereal with milk.
• You may take your usual medicines unless you have been instructed not to by the specialist doctor or nurse. If you take Desmopressin (DDAVP), please let the nurse know as soon as possible.

What happens during the test?

• On arrival you will meet the nurse who is responsible for the test. The nurse will explain the test and you will be given the opportunity to ask questions prior to the start of the test.
• A cannula – a fine plastic tube is inserted into a vein in your arm by the specialist nurse. This is used to take blood samples. There may be some discomfort for a few seconds.
• On arrival in the department you must not eat or drink any food or fluids.
• This test is performed under direct supervision. You will not be allowed to leave the department except under supervision. It is very important that you do not eat or drink because this will give false results.
• At hourly intervals throughout the day, you will be weighed, and a blood and urine sample will be collected by the nurse. The amount of urine passed each hour will be measured. It is important that you are weighed in the same clothes and shoes on each occasion.
• After approximately 6 hours you may be given an injection in your buttock. This injection helps your body to slow down urine and concentrate urine production. The nurse will decide if and when this is required.
• Further blood and urine samples will be collected hourly by the nurse. At some point later in the day after your injection, the nurse will tell you when you are allowed to eat and drink. You will then be given food and fluids.
• If you do not require an injection, the test is complete. You will then be given food and fluids and you will be allowed to go home.
• The nurse will tell you when the test is complete.
• Your blood pressure will be checked as appropriate during the test.
• At the end of the test the tube (cannula) will be removed from your arm, and a small dressing applied. The dressing may be removed once you get home.

Are there any side effects?

• You may feel very thirsty during the test. If the results suggest that you are becoming very dehydrated during the course of the test, the test will finish early. The nurse will tell you if this is necessary.
• You may feel tired during the test and you may get a headache.
• It is important that you feel well enough before you are allowed home.

What happens after the test?

• On completion of the test you will be safe to resume your normal daily activities.
• At the end of the test the nurse will discuss the results with you. If you require any treatment, you will be given the medicine to take home with you. The results will be available at your next clinic visit or a letter will be sent to you and your GP.
• The nurse will arrange a further appointment if necessary.

If you require more details please contact the Specialist Nurses in Endocrinology:
Tel: 01274 382019 Monday – Friday between 8.00am and 4.00pm except Bank Holidays