Corrected calcium formula
Adjusted calcium = total calcium + 0.02 × (40 − albumin)
Calcium in mmol/L, albumin in g/L
Many labs report adjusted calcium already. Check your lab’s method and range.
Action thresholds
| Adjusted calcium (mmol/L) | Action |
|---|
| 3.5 or more | Same-day admission |
| 3.0–3.4 | Admit if symptomatic; otherwise repeat urgently with PTH |
| 2.6–2.9 | Repeat with PTH, U&E and vitamin D |
| 2.2–2.6 | Usual range |
| Below 1.9 | Same-day admission, especially with symptoms |
Persistent unexplained hypercalcaemia can indicate cancer (NICE NG12).
Frequently asked questions
How do you correct calcium for albumin?
Add 0.02 mmol/L for every g/L that albumin is below 40, or subtract if above.
What level of calcium needs admission?
3.5 mmol/L or more, or 3.0 to 3.4 with symptoms.
What tests go with a high calcium?
PTH, U&E, vitamin D and a review of thiazides, lithium and supplements.
References
- Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. BMJ 1973;4:643–6.
- NICE CKS. Hypercalcaemia. cks.nice.org.uk
MedToolbox supports, and does not replace, clinical judgement, national guidance and local policy.
