Calcium [Ca]

Calcium sticks strongly to proteins in the blood, especially albumin. This means that if albumin is low, calcium levels will be measured as low, even though the level of 'free' (ionised, or unbound) calcium in the blood may be normal. The adjusted calcium value aims to compensate for this. (Details: the usual formula is to add or subtract 0.02 mmol/l for each g/l that albumin is over or under 40g/l.). Measuring an IONIZED CALCIUM (normal 1.16-1.31) gets round this problem, but isn't such an easy test to do.

less than 1.8
Very low - Likely to cause symptoms (if albumin is normal)
less than 2.1
Low. 'Low' calcium may be normal in patients with a low serum albumin.
Normal in patients with a normal serum albumin
Too high
Likely to make you very unwell.

Calcium in kidney disease

Low calcium is usual in people with untreated kidney disease, mostly because the healthy kidney is involved in processing of Vitamin D. Low calcium causes an increase in PTH, which then moves calcium out of bones and thins them. Special types of vitamin D are used to treat this (alfacalcidol, calcitriol). However these, and some phosphate binders, and parathyroid hormone may cause high calcium levels. So calcium needs to be checked regularly in people with kidney disease. Normal = 2.1-2.6 mmol/litre (8.4-10.4 mg/dl).

Mixed up calcium, phosphate, and PTH are the cause of renal bone disease, and probably of some other troubles that occur in kidney failure.

More info

More info about Calcium from Lab Tests Online

More info about Renal (kidney) Bone Disease from the NKF...


This page created 6th December 2004, last modified July 7, 2015, on the PatientView website