BLOOD SCIENCES
DEPARTMENT OF CLINICAL BIOCHEMISTRY
Title of Document: Water Deprivation Test in Adults
Q Pulse Reference No: BS/CB/DCB/EN/16 Version NO: 5
Authoriser: Sadie Redding Page 1 of 4
WATER DEPRIVATION TEST
Introduction
Diabetes insipidus (DI) involves deficient production or lack of effective action of antidiuretic
hormone (ADH or arginine vasopressin). ADH stimulates the kidney to conserve fluid. Deficient
production of ADH or lack of effective action of ADH causes a high urine output, thirst, dehydration,
and low blood pressure in advanced cases.
Disease of the hypothalamus/pituitary gland leading to a deficiency in ADH production is called
cranial or central DI. Disease of the kidney leading to lack of response of the kidney to fluid
conserving action of ADH is called nephrogenic DI.
The principle of the water deprivation test is to assess the ability of the patient to concentrate urine when
fluids are withheld. Water deprivation should normally cause increased secretion of ADH, resulting in the
production of small volumes of concentrated urine.
Initial tests
Polyuria should be confirmed by 24hour urine volume.
Rule out diabetes, UTI, hypercalcaemia, hypokalaemia, renal failure and thyrotoxicosis.
Morning urine osmolality >600mOsm/kg rules out DI and therefore a water deprivation test is not
necessary.
Preparation
Please contact the Duty Biochemist at least 24 hours before the test (ext.48437)
Normal dinner and fluids are allowed the night before the test. No alcohol or caffeine.
7am light breakfast but NO fluids, tea, coffee or smoking.
Supervision is required throughout to assess compliance and safety.
Contraindications
Hypovolaemia or hypernatraemia
Procedure
Print out a worksheet and record results in the table (appendix 1).
Please clearly label all blood and urine samples; the TIME of collection is essential.
1. 8 am:
a) Empty bladder, record the volume, and send urine osmolality
b) Take a serum osmolality
c) Record the patient's weight.
2. Then for the next 8 hours check: Urine osmolality and weight every hour
Serum osmolality every 2 hours
N.B. Stop the test and call the endocrine SPR if the patient's weight decreases by more than 3% of
body weight (or by 4kg) or the serum osmolality rises >300mOsm/kg.
3. If the urine osmolality at 4 p.m. remains <600mOsm/kg proceed with the desmopressin test.
a) Desmopressin (DDAVP) 20mcg intranasally or 2 µg intramuscularly
b) Can eat and drink freely
c) Hourly urine volumes and osmolality until 8.30pm.
