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What is Free Water Deficit?
Free water deficit describes the volume of pure water required to reduce an elevated serum sodium toward a chosen target without changing total body solute. It is estimated from total body water and the ratio between measured sodium and target sodium. Because total body water varies with age sex and body composition, estimations often use weight based fractions. Clinically, the deficit guides hypotonic fluid replacement and helps plan safe correction rates. Rapid correction risks cerebral edema while inadequate replacement prolongs hypernatremia and dehydration. Typical practice replaces a portion initially then completes the remaining volume over twenty four to forty eight hours while monitoring electrolytes urine output and ongoing losses. Calculators support transparent math and documentation but cannot replace clinical judgment.
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Enter values and press Calculate to see the deficit, suggested average rate, and detailed math.