Albumin-adjusted (corrected) calcium: better reflects free calcium when albumin is abnormal.
What it is
Calculated from total calcium and albumin (formulae vary slightly by lab). Reported in mmol/L.
Albumin-adjusted (corrected) calcium applies a laboratory formula to total calcium based on albumin concentration. Formulae differ slightly between UK labs; always use the value your report prints rather than recalculating from the internet. Reported in mmol/L.
Why it matters
Used when total calcium may mislead because of low or high albumin. Persistent abnormalities still need clinical interpretation and sometimes ionised calcium.
This guide is educational only and cannot diagnose you. Discuss results, especially anything outside your laboratory’s reference interval, or that does not match how you feel, with a GP or other appropriately qualified clinician.
When albumin is low (illness, inflammation, undernutrition), total calcium falls even if free calcium is acceptable: adjustment reduces that artefact. Persistently abnormal adjusted calcium still needs clinical work-up (PTH, vitamin D, kidney function, medicines).
This guide is educational only and cannot diagnose you. Discuss results, especially anything outside your laboratory’s reference interval, or that does not match how you feel, with a GP or other appropriately qualified clinician.
How it affects the body
Adjusting for albumin approximates the physiologically active calcium fraction when protein binding shifts.
Roughly half of plasma calcium is bound to albumin. Only the ionised fraction is biologically active at nerves, muscle, and clotting proteins. Adjustment is a pragmatic estimate of that active fraction when direct ionised calcium is not measured.
For athletes
Helpful after ultras when albumin has dipped, still not a licence to self-supplement calcium.
After prolonged events albumin can dip with inflammation; adjusted calcium is the fairer number then. Bone-loading athletes with abnormal calcium still need endocrine/bone review: training stress is not an explanation to skip.
