MedeliX
Start asking

Corrected calcium

Total calcium corrected for albumin

Sources last checked: 2026-10-13

Corrected calcium

Total calcium corrected for albumin

Correction factor
Fill in every field to see the result.

Uses Payne's published slope (1 mg/dL calcium per 1 g/dL albumin). The common 0.8 variant and laboratory-specific equations give lower values; the correction performs poorly in critical illness and advanced CKD, where ionised calcium is the more reliable measure.

Source: Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. BMJ 1973;4(5893):643-646.Open

Interpretation

Low< 8.5 mg/dL (≈ 2.12 mmol/L).
Typical reference range8.5–10.5 mg/dL (≈ 2.12–2.62 mmol/L); laboratory reference ranges vary.
Raised> 10.5 to < 12.0 mg/dL (< 3.0 mmol/L) — mild hypercalcaemia, often asymptomatic.
Moderate hypercalcaemia12.0–14.0 mg/dL (3.0–3.5 mmol/L) — SfE guidance describes prompt treatment as usually indicated when symptomatic.
Severe hypercalcaemia> 14.0 mg/dL (> 3.5 mmol/L) — SfE guidance classes this as severe, requiring urgent correction.

What is the Corrected calcium?

Corrected (albumin-adjusted) calcium estimates what total serum calcium would be at a normal albumin concentration, because about 40 % of calcium is protein-bound. Payne and colleagues derived the classic adjustment in 1973 from 200 specimens in a UK laboratory: adjusted calcium = calcium − albumin + 4.0 (mg/dL and g/dL). Hypercalcaemia severity bands follow the Society for Endocrinology emergency guidance.

When to use it

  • Interpreting total calcium when albumin is low or high (liver disease, malnutrition, nephrotic syndrome, acute illness).
  • Assessing suspected hyper- or hypocalcaemia before or while waiting for ionised calcium.
  • Following trends in patients whose albumin is changing.

When not to use it

  • Critical illness, advanced CKD or acid-base disturbances — the correction is unreliable there; ionised calcium is the direct measurement.
  • When ionised calcium is already available — it is the physiologically relevant value.
  • With paraproteinaemia, where calcium can bind to the paraprotein.

How it is calculated

Adjusted Ca (mg/dL) = measured Ca (mg/dL) − albumin (g/dL) + 4.0 SI equivalent: adjusted Ca (mmol/L) ≈ Ca + 0.025 × (40 − albumin in g/L) 1 mmol/L = 4.008 mg/dL

Clinical pearls and limitations

  • Uses Payne's published slope (1 mg/dL calcium per 1 g/dL albumin). The common 0.8 variant and laboratory-specific equations give lower values; the correction performs poorly in critical illness and advanced CKD, where ionised calcium is the more reliable measure.
  • SI units: 1 mmol/L calcium = 4.008 mg/dL; Payne's slope corresponds to about 0.025 mmol/L per g/L albumin.
  • Many laboratories (especially in the UK) report their own albumin-adjusted calcium with a locally derived equation — where provided, that value reflects the local calibration.
  • The widely used 0.8 mg/dL per g/dL variant gives a smaller correction than Payne's published formula; know which one you are comparing with.
  • Take blood with minimal venous stasis — a prolonged tourniquet raises albumin and total calcium.
  • In hypercalcaemia, PTH separates the main causes: high/normal PTH suggests hyperparathyroidism, suppressed PTH suggests malignancy or another PTH-independent cause.

Frequently asked questions

What is the formula for corrected calcium?

Payne 1973: adjusted calcium (mg/dL) = measured calcium (mg/dL) − albumin (g/dL) + 4.0. In SI units this is about calcium (mmol/L) + 0.025 × (40 − albumin in g/L). Many labs and websites use 0.8 per g/dL (0.02 per g/L) instead.

Corrected calcium or ionised calcium?

Ionised calcium is the biologically active fraction and is preferred in critical illness, CKD and acid-base disorders, where albumin correction frequently misclassifies patients.

When is hypercalcaemia dangerous?

The Society for Endocrinology classes adjusted calcium < 3.0 mmol/L (12 mg/dL) as usually asymptomatic, 3.0–3.5 mmol/L as often needing prompt treatment, and > 3.5 mmol/L (14 mg/dL) as requiring urgent correction.

Evidence and guidelines

  1. Primary source: Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. BMJ 1973;4(5893):643-646.
  2. Walsh J, Gittoes N, Selby P. Society for Endocrinology endocrine emergency guidance: emergency management of acute hypercalcaemia in adult patients. Endocr Connect 2016;5(5):G9-G11 (severity bands 3.0 and 3.5 mmol/L).
  3. Payne RB, Carver ME, Morgan DB. Interpretation of serum total calcium: effects of adjustment for albumin concentration. J Clin Pathol 1979;32(1):56-60.

Have a follow-up question?

Medelix answers clinical questions from current guidelines and studies — every statement with its source.

Ask Medelix about the Corrected calcium

Related calculators

Embed this calculatorFree to use on your website, intranet or teaching page. Copy the code below.
<iframe src="https://medelix.ai/en/embed/corrected-calcium" title="Corrected calcium – Medelix" width="100%" height="620" style="border:0;max-width:720px" loading="lazy"></iframe> <p><a href="https://medelix.ai/en/calculators/corrected-calcium">Corrected calcium calculator by Medelix</a></p>

For healthcare professionals and medical students. These tools support, and do not replace, clinical judgement. Always check results against the original source and your local protocols.