Health

Serum Osmolality Calculator (Calculated)

Calculate serum osmolality from routinely measured solutes. Conventional formula Osm = 2 × Na + Glucose/18 + BUN/2.8 (Na in mmol/L, glucose & BUN in mg/dL), or the SI-unit form Osm = 2 × Na + Glucose + Urea (all mmol/L). An optional ethanol term (EtOH/4.6) is available when a toxic-alcohol ingestion is being considered. Normal range ≈ 275–295 mOsm/kg. Values < 275 suggest hypo-osmolality (SIADH, primary polydipsia, adrenal insufficiency, hypothyroidism); values > 295 suggest hyperosmolality (hyperglycemia/HHS, hypernatremia, uremia, mannitol, toxic alcohols — the latter also raise the osmolar gap, so measure osmolality and compute the gap). Derived from Dorwart 1975, Rasouli 2014, and MDCalc. Not medical advice.

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Quick start

Call this tool from your code in three languages.

cURL

curl -X POST 'https://api.elysiatools.com/en/api/tools/serum-osmolality-calculator' \
  -H 'Content-Type: application/json' \
  -d '{"unitSystem":"conventional","sodium":140,"glucose":110,"bunOrUrea":14,"ethanol":0,"decimalPlaces":1}'

API reference

Send a POST request with your inputs as JSON. File parameters require a separate upload first.

Endpoint

HTTP

POST https://api.elysiatools.com/en/api/tools/serum-osmolality-calculator

Parameters

Name	Type	Required	Description
unitSystem	select	Yes	—
sodium	number	Yes	Serum sodium (mmol/L), always in mmol/L regardless of unit system. Physiologic range ~120–160.
glucose	number	Yes	Serum glucose. mg/dL under Conventional units, mmol/L under SI units.
bunOrUrea	number	Yes	BUN in mg/dL under Conventional units, or serum urea in mmol/L under SI units.
ethanol	number	No

MCP integration

Add this tool to your Model Context Protocol server so AI agents can list and call it.

Server configuration

Add this block to your MCP client configuration:

mcp.json

{
  "mcpServers": {
    "elysiatools-serum-osmolality-calculator": {
      "name": "serum-osmolality-calculator",
      "description": "Calculate serum osmolality from routinely measured solutes. Conventional formula Osm = 2 × Na + Glucose/18 + BUN/2.8 (Na in mmol/L, glucose & BUN in mg/dL), or the SI-unit form Osm = 2 × Na + Glucose + Urea (all mmol/L). An optional ethanol term (EtOH/4.6) is available when a toxic-alcohol ingestion is being considered. Normal range ≈ 275–295 mOsm/kg. Values < 275 suggest hypo-osmolality (SIADH, primary polydipsia, adrenal insufficiency, hypothyroidism); values > 295 suggest hyperosmolality (hyperglycemia/HHS, hypernatremia, uremia, mannitol, toxic alcohols — the latter also raise the osmolar gap, so measure osmolality and compute the gap). Derived from Dorwart 1975, Rasouli 2014, and MDCalc. Not medical advice.",
      "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=serum-osmolality-calculator",
      "command": "",
      "args": [],
      "env": {},
      "isActive": true,
      "type": "sse"
    }
  }
}

List available tools

After connecting to the SSE endpoint, list the exposed tools:

tools/list

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Call this tool

Invoke the tool by its id, passing arguments built from its parameters:

tools/call

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "serum-osmolality-calculator",
    "arguments": {
  "unitSystem": "conventional",
  "sodium": 140,
  "glucose": 110,
  "bunOrUrea": 14,
  "ethanol": 0,
  "decimalPlaces": 1
}
  }
}

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