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Free water clearance (FWC) Calculator

FWC = UV x (1-(U osm / P osm))
UV : Urine flow rate (L/day)
* If the 24-hour urine volume is not entered, only a POSITIVE or NEGATIVE result will be provided.







FWC POSITIVE: Indicates net excretion of free water, typically seen in states of water excess or when hypotonic urine is excreted. It reflects the body’s effort to eliminate excess water.
FWC NEGATIVE: Indicates net retention of free water, typically seen in states of dehydration or under the influence of antidiuretic hormone (ADH), where the kidneys actively conserve water by producing hypertonic urine.

Nephrology
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