# Corrected (Albumin-Adjusted) Calcium Calculator
> Free corrected calcium calculator. Ca_corrected = Ca + 0.8 × (4 − albumin). Standard adjustment for hypoalbuminemia. Education only.

## Overview

Corrected (albumin-adjusted) calcium accounts for the protein-binding behaviour of calcium when serum albumin is low. The standard formula adds 0.8 mg/dL to measured calcium for every 1 g/dL that albumin falls below 4 g/dL. The correction is widely used in hospital medicine because hypoalbuminaemic patients commonly show low total calcium with normal ionised calcium. Direct measurement of ionised calcium remains the gold standard when precise calcium status is needed (e.g. critical illness, citrate toxicity, parathyroid evaluation).

## Who this is for

- Internal medicine and hospitalist trainees
- Critical care clinicians
- Endocrinology consult services

## How to interpret the result

| Score / band | Meaning |
|---|---|
| Hypocalcaemia (corrected < 8.5) | Workup for vitamin D, PTH, magnesium, renal function. |
| Normocalcaemia (8.5–10.5) | Within most reference ranges (verify your laboratory). |
| Hypercalcaemia (corrected > 10.5) | Workup for primary hyperparathyroidism, malignancy, granulomatous disease. |

## Cited source

**Endocrine Society Clinical Practice Guideline (Hypercalcaemia of Malignancy)** (2023) — Endocrine Society

_Primary publication:_ Payne RB et al., BMJ 1973

## FAQs

### When should I check ionised calcium instead?

Critical illness, sepsis, large transfusions (citrate effect), severe acid-base disturbance, parathyroid surgery, and discordant clinical picture all favour direct ionised calcium measurement.

### Is the 0.8 correction always accurate?

It is an approximation derived in 1973 cohorts. Validation studies in modern populations show reasonable but imperfect performance — useful at the bedside but not a substitute for ionised calcium when precise.

### Does the correction apply when albumin is high?

The formula is symmetric (corrected Ca falls below measured Ca when albumin > 4), but elevated albumin is uncommon clinically.

### Should I correct for both albumin and pH?

Acid-base shifts ionised calcium independent of total calcium. The albumin correction does not address pH; in metabolic alkalosis or acidosis, ionised calcium is preferred.

### Can I use this in paediatrics?

The correction is broadly used in paediatrics but has more limited validation. Consult paediatric reference ranges and consider ionised calcium for definitive evaluation.

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_Rounds AI is a citation-first clinical AI assistant. It supports clinical reasoning by surfacing cited information and is not a substitute for independent clinical judgement._