Water Deprivation Test Interpreter

Pre-Desmo Urine Osm

Post-Desmo Urine Osm

Serum Osm (End of Step 1)

Note: Step 1 (Water deprivation) should stop when Posm > 295 mOsm/kg or weight loss > 3%. Desmopressin (Step 2) is then given to check the kidney's response to the missing or ineffective ADH.

Guidelines & Evidence

Verified

Last Review: 2026

When to Use

Differential diagnosis of polyuria-polydipsia syndrome.

Distinguishing Central Diabetes Insipidus (DI) from Nephrogenic DI.

Confirming Primary (Psychogenic) Polydipsia.

Evaluating patient after exclusion of common causes (hypercalcaemia, hyperglycaemia, hypokalaemia).

Clinical Pearls

Interpretation Table

Diagnosis	Urine Osmo (Step 1)	Urine Osmo (Step 2)
Primary Polydipsia	> 600	No change
Central DI	< 300	Increases > 50%
Nephrogenic DI	< 300	Increases < 10%
Partial Central DI	300 – 600	Increases 10 – 50%

Diagnostic Safety

Always perform this test in a supervised inpatient setting. Patients with severe DI can rapidly become dangerously dehydrated during Step 1.

Last Comprehensive Review: 2026

Recent Journal Updates

JAMAJul 21, 2026

PCOS Is Now Called PMOS

Clinical Context

We think this has broad domain relevance to Water Deprivation Test Interpreter.

Emerging Infectious DiseasesJul 15, 2026

Targeted Wastewater Surveillance during the World Athletics Championship, Oregon, USA, 2022

Clinical Context

We think this might be relevant to the clinical guidance for Water Deprivation Test Interpreter.

Tropical Med & Intl HealthJul 10, 2026

Water Pollution and Perinatal or Neonatal Outcomes: A Scoping Review

Clinical Context

We think this might be relevant to the clinical guidance for Water Deprivation Test Interpreter.

Water Deprivation Test Interpreter

When to Use

When to Use

How it Works

Step 1: Water Deprivation

Step 2: Desmopressin Challenge

Clinical Pearls

Interpretation Table

Diagnostic Safety

The Evidence

Primary Source

Clinical review: Current state and future perspectives in the diagnosis of diabetes insipidus.

Recent Journal Updates

Water Deprivation Test Interpreter

When to Use

When to Use

How it Works

Step 1: Water Deprivation

Step 2: Desmopressin Challenge

Clinical Pearls

Interpretation Table

Diagnostic Safety

The Evidence

Primary Source

Clinical review: Current state and future perspectives in the diagnosis of diabetes insipidus.

Recent Journal Updates