Fluid deprivation test

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Fluid/water deprivation test
OPS-301 code 1-797

A fluid or water deprivation test is a medical test [1] which can be used to determine whether the patient has diabetes insipidus as opposed to other causes of polydipsia (a condition of excessive thirst that causes an excessive intake of water). The patient is required, for a prolonged period, to forgo intake of water completely, to determine the cause of the thirst.


This test measures changes in body weight, urine output, and urine composition when fluids are withheld. Sometimes measuring blood levels of ADH (a synonym for vasopressin) during this test is also necessary.

If there is no change in the water loss despite fluid deprivation, desmopressin may be administered to distinguish between the two types of diabetes insipidus which are central & nephrogenic diabetes insipidus.

The time of deprivation may vary from 4 to 18 hours. [2]

The serum osmolality and urine osmolality are both measured in the test.

Interpretation of WDT

The conditions can be distinguished in the following way:

ConditionUrine osmolality in mOsm/kg, after fluid deprivation [3] After desmopressin [3] or vasopressin
Normal> 800> 800 (<10% increase)
a defect in ADH production (central/neurogenic diabetes insipidus)< 300> 800 (>50% increase)
a defect in the kidneys' response to ADH production (nephrogenic diabetes insipidus)< 300< 500 (<50% increase)
excessive intake of fluid (primary polydipsia)> 500> 500 (<10% increase)

Related Research Articles

Diabetes insipidus Condition characterized by large amounts of dilute urine and increased thirst

Diabetes insipidus (DI) is a condition characterized by large amounts of dilute urine and increased thirst. The amount of urine produced can be nearly 20 liters per day. Reduction of fluid has little effect on the concentration of the urine. Complications may include dehydration or seizures.

Dehydration Deficit of total body water

In physiology, dehydration is a deficit of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mild dehydration can also be caused by immersion diuresis, which may increase risk of decompression sickness in divers.


Polyuria is excessive or an abnormally large production or passage of urine. Increased production and passage of urine may also be termed diuresis. Polyuria often appears in conjunction with polydipsia, though it is possible to have one without the other, and the latter may be a cause or an effect. Primary polydipsia may lead to polyuria. Polyuria is usually viewed as a symptom or sign of another disorder, but it can be classed as a disorder, at least when its underlying causes are not clear.


Thirst is the craving for potable fluids, resulting in the basic instinct of animals to drink. It is an essential mechanism involved in fluid balance. It arises from a lack of fluids or an increase in the concentration of certain osmolites, such as sodium. If the water volume of the body falls below a certain threshold or the osmolite concentration becomes too high, structures in the brain detect changes in blood constituents and signal thirst.

Clinical urine tests

Clinical urine tests is an examination of urine for certain physical properties, solutes, cells, casts, crystals, organisms, or particulate matter, and mainly serves for medical diagnosis. The word is a blend of the words urine and analysis. Urine culture and urine electrolyte levels are part of urinalysis.

Polydipsia is excessive thirst or excess drinking. The word derives from the Greek πολυδίψιος (poludípsios) "very thirsty", which is derived from πολύς + δίψα. Polydipsia is a nonspecific symptom in various medical disorders. It also occurs as an abnormal behaviour in some non-human animals, such as in birds.

Desmopressin Medication

Desmopressin, sold under the trade name DDAVP among others, is a medication used to treat diabetes insipidus, bedwetting, hemophilia A, von Willebrand disease, and high blood urea levels. In hemophilia A and von Willebrand disease, it should only be used for mild to moderate cases. It may be given in the nose, by injection into a vein, by mouth, or under the tongue.

Electrolyte imbalance

Electrolyte imbalance, or water-electrolyte imbalance, is an abnormality in the concentration of electrolytes in the body. Electrolytes play a vital role in maintaining homeostasis in the body. They help to regulate heart and neurological function, fluid balance, oxygen delivery, acid–base balance and much more. Electrolyte imbalances can develop by consuming too little or too much electrolyte as well as excreting too little or too much electrolyte.

Hypernatremia, also spelled hypernatraemia, is a high concentration of sodium in the blood. Early symptoms may include a strong feeling of thirst, weakness, nausea, and loss of appetite. Severe symptoms include confusion, muscle twitching, and bleeding in or around the brain. Normal serum sodium levels are 135–145 mmol/L. Hypernatremia is generally defined as a serum sodium level of more than 145 mmol/L. Severe symptoms typically only occur when levels are above 160 mmol/L.

Hyperchloremia is an electrolyte disturbance in which there is an elevated level of the chloride ions in the blood. The normal serum range for chloride is 96 to 106 mEq/L, therefore chloride levels at or above 110 mEq/L usually indicate kidney dysfunction as it is a regulator of chloride concentration. As of now there are no specific symptoms of hyperchloremia, however, it can be the influenced by multiple abnormalities that cause a loss of electrolyte-free fluid, loss of hypotonic fluid, or increased administration of sodium chloride. These abnormalities are caused by diarrhea, vomiting, increased sodium chloride intake, renal dysfunction, diuretic use, and diabetes. Hyperchloremia should not be mistaken for hyperchloremic metabolic acidosis as hyperchloremic metabolic acidosis is characterized by two major changes: a decrease in blood pH and bicarbonate levels, as well as an increase in blood chloride levels. Instead those with hyperchloremic metabolic acidosis are usually predisposed to hyperchloremia.

Water intoxication Potentially fatal overhydration

Water intoxication, also known as water poisoning, hyperhydration, overhydration, or water toxemia, is a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside safe limits by excessive water intake.

Nocturia is defined by the International Continence Society (ICS) as “the complaint that the individual has to wake at night one or more times for voiding .” The term is derived from Latin nox, night, and Greek [τα] ούρα, urine. Causes are varied and can be difficult to discern. Although not every patient needs treatment, most people seek treatment for severe nocturia, waking up to void more than 2–3 times per night.

Plasma osmolality measures the body's electrolyte–water balance. There are several methods for arriving at this quantity through measurement or calculation.

Nephrogenic diabetes insipidus (NDI) is a form of diabetes insipidus primarily due to pathology of the kidney. This is in contrast to central or neurogenic diabetes insipidus, which is caused by insufficient levels of antidiuretic hormone. Nephrogenic diabetes insipidus is caused by an improper response of the kidney to ADH, leading to a decrease in the ability of the kidney to concentrate the urine by removing free water.

Primary polydipsia

Primary polydipsia, or psychogenic polydipsia, is a form of polydipsia characterised by excessive fluid intake in the absence of physiological stimuli to drink. Psychogenic polydipsia which is caused by psychiatric disorders, often schizophrenia, is often accompanied by the sensation of dry mouth. Some forms of polydipsia are explicitly non-psychogenic. Primary polydipsia is a diagnosis of exclusion.

Urine specific gravity

Specific gravity, in the context of clinical pathology, is a urinalysis parameter commonly used in the evaluation of kidney function and can aid in the diagnosis of various renal diseases.

Central diabetes insipidus, also called neurogenic diabetes insipidus, is a type of diabetes insipidus due to a lack of vasopressin (ADH) production in the brain. Vasopressin acts to increase the volume of blood (intravascularly), and decrease the volume of urine produced. Therefore, a lack of it causes increased urine production and volume depletion.

Diabetes usually refers to diabetes mellitus, a group of metabolic diseases in which a person has high blood glucose levels over a prolonged period.

History of diabetes

The condition known today as diabetes is thought to have been described in the Ebers Papyrus. Ayurvedic physicians first noted the sweet taste of diabetic urine, and called the condition madhumeha. The term "diabetes" traces back to Demetrius of Apamea. For a long time, the condition was described and treated in traditional Chinese medicine as xiāo kě. Physicians of the medieval Islamic world, including Avicenna, have also written on diabetes. Early accounts often referred to diabetes as a disease of the kidneys. In 1674, Thomas Willis suggested that diabetes may be a disease of the blood. Johann Peter Frank is credited with distinguishing diabetes mellitus and diabetes insipidus in 1794.


Adipsia, also known as hypodipsia, is a symptom of inappropriately decreased or absent feelings of thirst. It involves an increased osmolality or concentration of solute in the urine, which stimulates secretion of antidiuretic hormone (ADH) from the hypothalamus to the kidneys. This causes the person to retain water and ultimately become unable to feel thirst. Due to its rarity, the disorder has not been the subject of many research studies.


  1. Choices, NHS. "Diabetes insipidus - Diagnosis - NHS Choices". www.nhs.uk. Retrieved 2016-03-14.
  2. Norman Lavin (1 April 2009). Manual of Endocrinology and Metabolism. Lippincott Williams & Wilkins. pp. 67–. ISBN   978-0-7817-6886-3 . Retrieved 12 November 2010.
  3. 1 2 Water deprivation and desmopressin test at GPnote