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Corrected Sodium Calculator

Corrects measured serum sodium for the dilutional effect of hyperglycaemia using the Katz 1.6 mmol/L and Hillier 2.4 mmol/L factors per 100 mg/dL of glucose above 100 mg/dL.

When to use

A patient has hyperglycaemia (e.g. diabetic ketoacidosis or hyperosmolar state) and you want the sodium that would be measured at a normal glucose.

Do not use when: Glucose is normal (no correction applies) or the hyponatraemia has other causes such as pseudohyponatraemia from lipids or proteins.

Formula

corrected_Na = sodium_mmol_l + factor × (glucose_mg_dl − 100) / 100, with factor 1.6 (Katz) or 2.4 (Hillier); the glucose excess is taken as 0 when glucose ≤ 100 mg/dL; glucose_mg_dl = mmol/L × 18.016

Katz (1973) derived 1.6 theoretically; Hillier (1999) measured 2.4 experimentally and found the effect larger above 400 mg/dL, so both are reported. Results are informational only and not a substitute for clinical judgement or medical advice.

Inputs

Parameter	Type	Unit	Required	Description
`sodium_mmol_l`	number	mmol/L	yes	Measured serum sodium. Range: ≥ 100, ≤ 200
`glucose`	number		yes	Plasma glucose in the unit given by glucose_unit. Range: > 0, ≤ 5000
`glucose_unit`	enum: mg_dl \| mmol_l		default mg_dl	Unit of the glucose value (1 mmol/L = 18.016 mg/dL).

Outputs

Output	Type	Unit	Description
`corrected_sodium_katz_mmol_l`	number	mmol/L	Sodium + 1.6 per 100 mg/dL glucose above 100.
`corrected_sodium_hillier_mmol_l`	number	mmol/L	Sodium + 2.4 per 100 mg/dL glucose above 100.
`glucose_mg_dl`	number	mg/dL	Glucose used in the formula, in mg/dL.
`correction_katz_mmol_l`	number	mmol/L	Amount added to the measured sodium by the Katz factor.

Example

Na 130, glucose 500 mg/dL: {"sodium_mmol_l":130,"glucose":500,"glucose_unit":"mg_dl"} → {"corrected_sodium_katz_mmol_l":136.4,"corrected_sodium_hillier_mmol_l":139.6,"correction_katz_mmol_l":6.4}

Na 128, glucose 30 mmol/L: {"sodium_mmol_l":128,"glucose":30,"glucose_unit":"mmol_l"} → {"corrected_sodium_katz_mmol_l":135.1,"corrected_sodium_hillier_mmol_l":138.6,"glucose_mg_dl":540.5}

GET https://tttkmbb.com/api/v1/calculate/corrected-sodium?sodium_mmol_l=130&glucose=500&glucose_unit=mg_dl

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/corrected-sodium (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/corrected-sodium · Markdown: https://tttkmbb.com/medical/corrected-sodium.md · JSON definition: https://tttkmbb.com/medical/corrected-sodium.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="corrected-sodium"
OpenAPI operationId: calculate_corrected_sodium
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Which factor should I use?

1.6 is the traditional textbook factor; 2.4 fits experimental data better, particularly when glucose exceeds 400 mg/dL. Reporting both brackets the likely true value.

Does the corrected sodium replace the measured value?

No. It estimates what sodium will be once glucose is normalised, which helps judge total-body water and sodium status during treatment.

Related calculators

Glucose Unit Converter — Convert glucose between mg/dL and mmol/L.
Anion Gap Calculator — Assess the acidosis that often accompanies severe hyperglycaemia.