# Serum Osmolality Calculator (Worthley 1987 + Osmolar Gap) > Serum Osmolality Calculator (Worthley 1987 + Osmolar Gap) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14). Calculates estimated serum osmolality using the Worthley 1987 formula (2×Na + glucose/18 + BUN/2.8) and optionally computes the osmolar gap when a measured osmolality is provided. ## Facts - Endpoint: GET https://api.magentlab.com/api/calc/serum_osmolality - Price: $0.005/call - Payment: x402 - Status: unknown - Last checked: 2026-09-14 - Activations on Zero: 0 - Tags: x402 - Canonical page: https://www.zero.xyz/c/serum-osmolality-calculator-worthley-1987-osmolar-gap-f6029937 - Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_qALGTWf11pwZOGGB5KAkO Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently. ## How to call it through Zero Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`): ```sh zero fetch --capability serum-osmolality-calculator-worthley-1987-osmolar-gap-f6029937 ``` Example prompt: Calculate the estimated serum osmolality for a patient with sodium 138 mmol/L, BUN 22 mg/dL, and glucose 108 mg/dL — and if the measured osmolality came back at 310 mOsm/kg, include the osmolar gap too. ## When to prefer this Use this endpoint when you need a fast, deterministic, citation-backed serum osmolality calculation following the Worthley 1987 formula, especially when you also want an osmolar gap derived from a measured value. Prefer this over manual arithmetic to ensure correct unit conversions (glucose mmol/L support) and validated input ranges. Not a substitute for a freezing-point osmometer or clinical diagnosis. ## Known failure modes - Missing required parameters (sodium_mmol_l or bun_mg_dl not provided) — returns validation error - Sodium out of range (110–160 mmol/L) — returns range error - BUN out of range (1–200 mg/dL) — returns range error - Glucose out of range (50–1000 mg/dL or 2.8–55.5 mmol/L) — returns range error - Measured osmolality out of range (200–400 mOsm/kg) — returns range error - Payment not completed (x402 protocol) — returns 402 Payment Required ## How this service works Worthley 1987 calculated serum osmolality: 2×Na + glucose/18 + BUN/2.8. Optional osmolar gap when a measured osm is supplied. Deterministic published arithmetic with citation; not a measured freezing-point osmometer or a diagnosis. ## Output Returns the calculated serum osmolality in mOsm/kg using the Worthley 1987 formula (2×Na + glucose/18 + BUN/2.8). When a measured osmolality is supplied, also returns the osmolar gap (measured minus calculated). Includes citation metadata confirming the deterministic arithmetic used. ## Request schema (JSON Schema) ```json { "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": [ "sodium_mmol_l", "bun_mg_dl" ], "properties": { "bun_mg_dl": { "type": "number", "description": "Blood urea nitrogen in mg/dL (1-200)." }, "glucose_mg_dl": { "type": "number", "description": "Plasma glucose in mg/dL (50-1000). Provide this or glucose_mmol_l." }, "sodium_mmol_l": { "type": "number", "description": "Serum sodium in mmol/L (110-160)." }, "glucose_mmol_l": { "type": "number", "description": "Plasma glucose in mmol/L (2.8-55.5). Converted as mg/dL = mmol/L * 18.015." }, "measured_osm_mosm_kg": { "type": "number", "description": "Measured serum osmolality in mOsm/kg (200-400). When supplied, osm_gap_mosm_kg is returned." } } } }, "additionalProperties": false }, "output": { "type": "object", "required": [ "type" ], "properties": { "type": { "type": "string" }, "example": { "type": "object" } } } } } ``` ## Response schema (JSON Schema) ```json { "type": "json", "example": { "path": "/api/calc/serum_osmolality", "count": 2, "items": [ { "formula": "worthley", "citation": { "id": "worthley-1987", "doi": "10.1177/0310057X8701500214", "title": "For calculating osmolality, the simplest formula is the best", "source": "Anaesth Intensive Care. 1987;15(2):199-202", "authors": "Worthley LI, Guerin M, Pain RW" }, "bun_mg_dl": 14, "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.", "glucose_mg_dl": 90, "sodium_mmol_l": 140, "formula_expression": "calculated_osm_mosm_kg = 2 * sodium_mmol_l + glucose_mg_dl / 18 + bun_mg_dl / 2.8", "calculated_osm_mosm_kg": 290 }, { "formula": "worthley", "citation": { "id": "worthley-1987", "doi": "10.1177/0310057X8701500214", "title": "For calculating osmolality, the simplest formula is the best", "source": "Anaesth Intensive Care. 1987;15(2):199-202", "authors": "Worthley LI, Guerin M, Pain RW" }, "bun_mg_dl": 14, "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.", "glucose_mg_dl": 90, "sodium_mmol_l": 140, "formula_expression": "calculated_osm_mosm_kg = 2 * sodium_mmol_l + glucose_mg_dl / 18 + bun_mg_dl / 2.8", "calculated_osm_mosm_kg": 290 } ] } } ``` ## More - Live health (JSON, refreshed every minute): https://www.zero.xyz/c/serum-osmolality-calculator-worthley-1987-osmolar-gap-f6029937/health.json - [Zero catalog index](https://www.zero.xyz/llms.txt) - [Other services from api.magentlab.com](https://www.zero.xyz/host/api.magentlab.com/llms.txt)