Adjusted calcium

This is the harmonised UK adult range; the adjustment formula differs slightly between labs, so the figure is best compared within one lab.

Adjusted calcium, also printed as corrected calcium, is the total calcium recalculated by the laboratory to allow for the albumin level. Because about half of blood calcium is bound to albumin, a low albumin drags the total down without changing the free calcium that the body actually uses. The adjusted figure is the laboratory's estimate of what the calcium would be if albumin were average, and it is the calcium figure doctors in the UK usually read.

It is printed automatically on UK bone profiles whenever calcium and albumin are measured together. Doctors use it in place of the unadjusted calcium when looking into bone, kidney and parathyroid conditions, kidney stones, tiredness and some cancers.

• Overactive parathyroid glands, the commonest cause of a sustained rise in the general population
• Some cancers
• Large intakes of vitamin D or calcium supplements
• Water tablets of the thiazide type, and lithium
• Being bedbound for a long time
• Overactive thyroid and some other hormone conditions

• Low vitamin D
• Reduced kidney filtering
• Underactive parathyroid glands, including after neck surgery
• Low magnesium
• Some medicines used for bone, and some epilepsy medicines
• Acute pancreatitis and other short-term illnesses

• The adjustment assumes a normal relationship between calcium and albumin, which does not hold in very unwell people or with unusual blood proteins
• A tight or prolonged tourniquet raises it
• Different labs use slightly different formulas, so the value can shift by up to 0.1 when the lab changes

No fasting needed. Calculated from calcium and albumin on the same sample. Read alongside phosphate, PTH and vitamin D.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.