{"uid":"cap_1pKaeD4dOg5Tawc4p5IGK","slug":"magent-free-water-deficit-calculator-49792adb","name":"Magent Free Water Deficit Calculator","description":"Free water deficit from weight, sex, and measured Na using Adrogué–Madias TBW (0.6 male / 0.5 female). Deterministic published arithmetic with citation; not a water-replacement infusion protocol.","url":"https://api.magentlab.com/api/calc/free_water_deficit","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET","HEAD","DELETE"],"type":"string"},"headers":{"type":"object","additionalProperties":{"type":"string"}},"queryParams":{"type":"object","required":["sex","sodium_mmol_l"],"properties":{"sex":{"enum":["female","male"],"type":"string","description":"Sex used for TBW: 0.6 × weight (male) or 0.5 × weight (female)."},"weight_kg":{"type":"number","description":"Weight in kilograms. Provide weight_kg or weight_lb."},"weight_lb":{"type":"number","description":"Weight in pounds. Converted as kg = lb * 0.45359237."},"sodium_mmol_l":{"type":"number","description":"Measured serum sodium in mmol/L. Range 146-190 (hypernatremia)."},"desired_na_mmol_l":{"type":"number","description":"Target serum sodium in mmol/L (130-145), must be less than measured Na. Omitted uses 140."}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object"}}}}},"responseSchema":{"type":"json","example":{"path":"/api/calc/free_water_deficit","count":2,"items":[{"sex":"male","tbw_l":42,"formula":"adrogue_madias","citation":{"id":"adrogue-madias-hypernatremia-2000","doi":"10.1056/NEJM200005183422006","title":"Hypernatremia","source":"N Engl J Med. 2000;342(20):1493-1499","authors":"Adrogué HJ, Madias NE"},"weight_kg":70,"disclaimer":"Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.","sodium_mmol_l":160,"desired_na_mmol_l":140,"formula_expression":"TBW_L = 0.6 * weight_kg (male) or 0.5 * weight_kg (female); free_water_deficit_l = TBW_L * (sodium_mmol_l / desired_na_mmol_l - 1)","free_water_deficit_l":6},{"sex":"male","tbw_l":42,"formula":"adrogue_madias","citation":{"id":"adrogue-madias-hypernatremia-2000","doi":"10.1056/NEJM200005183422006","title":"Hypernatremia","source":"N Engl J Med. 2000;342(20):1493-1499","authors":"Adrogué HJ, Madias NE"},"weight_kg":70,"disclaimer":"Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.","sodium_mmol_l":160,"desired_na_mmol_l":140,"formula_expression":"TBW_L = 0.6 * weight_kg (male) or 0.5 * weight_kg (female); free_water_deficit_l = TBW_L * (sodium_mmol_l / desired_na_mmol_l - 1)","free_water_deficit_l":6}]}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_Cu0V8kvRyZidEfL8p9oFV","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates free water deficit from patient weight, sex, and measured serum sodium using the Adrogué–Madias TBW formula","exampleAgentPrompt":"Calculate the free water deficit for a male patient weighing 80 kg with a measured serum sodium of 158 mmol/L, targeting a sodium of 140 mmol/L.","exampleUseCases":[{"title":"ICU hypernatremia workup","prompt":"My ICU patient is a 65 kg female with a serum sodium of 162 mmol/L. What's her free water deficit using the Adrogué–Madias formula, targeting sodium of 140?"},{"title":"ED hypernatremia triage","prompt":"Quick calc: male patient, 195 lbs, sodium came back at 152 mmol/L — what's the free water deficit?"},{"title":"Nephrology consult documentation","prompt":"I need the Adrogué–Madias free water deficit for a 90 kg male with sodium of 168 mmol/L so I can document it in the consult note."}],"resultDescription":"Returns the computed free water deficit in liters based on Adrogué–Madias total body water fractions (0.6 × weight for males, 0.5 × weight for females), the measured serum sodium, and the desired target sodium. Includes the arithmetic breakdown and citation. Does not provide an infusion rate or replacement protocol.","failureModes":["Missing required parameters (sex or sodium_mmol_l) returns a 400-level error","Sodium value outside hypernatremic range (below 146 mmol/L) may be rejected or flagged as out-of-range","Weight not provided (neither weight_kg nor weight_lb) causes calculation failure","Desired sodium >= measured sodium returns an error since no deficit exists","Payment not included or insufficient USDC returns a 402 Payment Required response"],"whenToPreferThis":"Use this endpoint when you need a deterministic, citation-backed Adrogué–Madias free water deficit calculation for a hypernatremic patient and only have weight, sex, and serum sodium available. Prefer this over general clinical decision support tools when you need reproducible arithmetic tied to a published formula rather than an advisory system or infusion protocol generator.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T01:16:00.308Z","isFirstParty":false}