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Urine Anion Gap (UAG) Calculator

Calculate the Urine Anion Gap (UAG) to differentiate causes of normal-anion-gap (hyperchloremic) metabolic acidosis: UAG = (U_Na + U_K) − U_Cl, in mmol/L. The UAG is an inverse surrogate for urinary NH₄⁺ excretion. A negative UAG (typically −20 to −50) indicates appropriate high NH₄⁺ excretion → extrarenal (GI) bicarbonate loss (diarrhea, fistulae, ureteral diversions). A positive/high UAG indicates low NH₄⁺ excretion → renal tubular acidosis (distal/type 1, type 4 hypoaldosteronism, proximal/type 2 variable). Reference range ≈ 0 to +40 mmol/L. Caveats: unreliable with unmeasured urine anions (ketoacidosis, toluene/hippurate, D-lactate) or when urine sodium < 25 mmol/L (use urine osmolar gap instead). Derived from Batlle CJASN 2012, Ito 2025, Bonner AJKD 2025. Interpret with blood gas and full clinical context. Not medical advice.

json· JSON resultOpen tool

Quick start

Call this tool from your code in three languages.

cURL

curl -X POST 'https://api.elysiatools.com/en/api/tools/anion-gap-renal' \
  -H 'Content-Type: application/json' \
  -d '{"urineSodium":25,"urinePotassium":35,"urineChloride":120,"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/anion-gap-renal

Parameters

Name	Type	Required	Description
urineSodium	number	Yes	Urine sodium U_Na (mmol/L). Must be ≥0. Reliability drops below 25 mmol/L.
urinePotassium	number	Yes	Urine potassium U_K (mmol/L). Must be ≥0.
urineChloride	number	Yes	Urine chloride U_Cl (mmol/L). Must be ≥0.
decimalPlaces	number	No	—

Response format

JSON result

JSON

{
  "key": {...},
  "metadata": {
    "key": "value"
  },
  "error": "Error message (optional)",
  "message": "Notification message (optional)"
}

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-anion-gap-renal": {
      "name": "anion-gap-renal",
      "description": "Calculate the Urine Anion Gap (UAG) to differentiate causes of normal-anion-gap (hyperchloremic) metabolic acidosis: UAG = (U_Na + U_K) − U_Cl, in mmol/L. The UAG is an inverse surrogate for urinary NH₄⁺ excretion. A negative UAG (typically −20 to −50) indicates appropriate high NH₄⁺ excretion → extrarenal (GI) bicarbonate loss (diarrhea, fistulae, ureteral diversions). A positive/high UAG indicates low NH₄⁺ excretion → renal tubular acidosis (distal/type 1, type 4 hypoaldosteronism, proximal/type 2 variable). Reference range ≈ 0 to +40 mmol/L. Caveats: unreliable with unmeasured urine anions (ketoacidosis, toluene/hippurate, D-lactate) or when urine sodium < 25 mmol/L (use urine osmolar gap instead). Derived from Batlle CJASN 2012, Ito 2025, Bonner AJKD 2025. Interpret with blood gas and full clinical context. Not medical advice.",
      "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=anion-gap-renal",
      "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": "anion-gap-renal",
    "arguments": {
  "urineSodium": 25,
  "urinePotassium": 35,
  "urineChloride": 120,
  "decimalPlaces": 1
}
  }
}

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Urine Anion Gap (UAG) Calculator

json· JSON resultOpen tool

Name

Type

Required

Description

urineSodium

number

Yes

Urine sodium U_Na (mmol/L). Must be ≥0. Reliability drops below 25 mmol/L.

urinePotassium

number

Yes

Urine potassium U_K (mmol/L). Must be ≥0.

urineChloride

number

Yes

Urine chloride U_Cl (mmol/L). Must be ≥0.

decimalPlaces

number

—

{ "mcpServers": { "elysiatools-anion-gap-renal": { "name": "anion-gap-renal", "description": "Calculate the Urine Anion Gap (UAG) to differentiate causes of normal-anion-gap (hyperchloremic) metabolic acidosis: UAG = (U_Na + U_K) − U_Cl, in mmol/L. The UAG is an inverse surrogate for urinary NH₄⁺ excretion. A negative UAG (typically −20 to −50) indicates appropriate high NH₄⁺ excretion → extrarenal (GI) bicarbonate loss (diarrhea, fistulae, ureteral diversions). A positive/high UAG indicates low NH₄⁺ excretion → renal tubular acidosis (distal/type 1, type 4 hypoaldosteronism, proximal/type 2 variable). Reference range ≈ 0 to +40 mmol/L. Caveats: unreliable with unmeasured urine anions (ketoacidosis, toluene/hippurate, D-lactate) or when urine sodium < 25 mmol/L (use urine osmolar gap instead). Derived from Batlle CJASN 2012, Ito 2025, Bonner AJKD 2025. Interpret with blood gas and full clinical context. Not medical advice.", "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=anion-gap-renal", "command": "", "args": [], "env": {}, "isActive": true, "type": "sse" } } }

{ "jsonrpc": "2.0", "id": 2, "method": "tools/call", "params": { "name": "anion-gap-renal", "arguments": { "urineSodium": 25, "urinePotassium": 35, "urineChloride": 120, "decimalPlaces": 1 } } }