# 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.

- Calculator id: `corrected-sodium` · Category: Medical & Clinical (`medical`) · Tool name: `calculate_corrected_sodium`
- Canonical page: https://tttkmbb.com/medical/corrected-sodium · This document: https://tttkmbb.com/medical/corrected-sodium.md · JSON definition: https://tttkmbb.com/medical/corrected-sodium.json

## Purpose

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.

**Use when:** 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.

## Input

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

## Output

| Field | 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. |

## 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.

## Data Sources

- Katz MA (1973) Hyperglycemia-induced hyponatremia – calculation of expected serum sodium depression, N Engl J Med 289:843-844 — https://pubmed.ncbi.nlm.nih.gov/4763428/ (peer_reviewed, retrieved 2026-09-24)
- Hillier TA, Abbott RD, Barrett EJ (1999) Hyponatremia: evaluating the correction factor for hyperglycemia, Am J Med 106:399-403 — https://www.amjmed.com/article/S0002-9343(99)00055-8/abstract (peer_reviewed, retrieved 2026-09-24)

Data freshness: `static`. Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output.

## API

- `GET https://tttkmbb.com/api/v1/calculate/corrected-sodium?sodium_mmol_l=…&glucose=…`
- `POST https://tttkmbb.com/api/v1/calculate/corrected-sodium` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/corrected-sodium · OpenAPI operationId `calculate_corrected_sodium` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "corrected-sodium", "inputs": {…}}`

## Example

- Na 130, glucose 500 mg/dL: inputs `{"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: inputs `{"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
```

## Limitations

Glucose is normal (no correction applies) or the hyponatraemia has other causes such as pseudohyponatraemia from lipids or proteins. 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. All values are computed from the formula above; no measurement or live data is involved.

## 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

- [Glucose Unit Converter](https://tttkmbb.com/medical/glucose-unit-conversion.md) — Convert glucose between mg/dL and mmol/L.
- [Anion Gap Calculator](https://tttkmbb.com/medical/anion-gap.md) — Assess the acidosis that often accompanies severe hyperglycaemia.