Urine concentration test

Alternative names:

water deprivation test; water loading test

Normal values:

1.010 to 1.025 (normal specific gravity)
1.001 after water loading
more than 1.025 after water deprivation
concentrated (increase in specific gravity) after ADH administration

What abnormal results mean:

Increased urine specific gravity may indicate:

• dehydration
• diarrhea
• excessive sweating
• glucosuria
• heart failure (related to decreased blood flow to the kidneys)
• proteinuria
• renal arterial stenosis
• syndrome of inappropriate antidiuretic hormone secretion (SIADH)
• vomiting
• water restriction

Decreased urine specific gravity may indicate:

• excessive fluid intake
• diabetes insipidus; central
• renal failure (i.e., loss of ability to re-absorb water)
• glomerulonephritis
• pyelonephritis

Additional conditions under which the test may be performed:

• complicated UTI (pyelonephritis)
• diabetes insipidus; nephrogenic