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Hypercalceamia is diagnosed when there is an increase in corrected (or albumin adjusted) calcium concentration above the upper limit of 2.65 mmol/l (1).
- it is important to obtain adjusted (corrected) calcium levels since low albumin levels will alter the total serum calcium levels (1)
- tests should be repeated unless the patient has severe hpercalcaemia or symptoms which warrant immediate referral
- ionised calcium levels are not routinely done in primary care (1)
Patients with adjusted hypercalcaemia between 3 – 3.4 mmol/l and symptomatic or if adjusted levels are >.3.4 mmol/l should be admitted to a hospital for urgent treatment (1).
If the hypercalcaemia is mild or moderate, look for an underlying cause.
- possible biochemical indicators of malignancy include low plasma albumin, low chloride, raised phosphate, raised alkaline phosphatase, alkalosis and hypokalaemia.
- possible biochemical indicators of hyperparathyroidism are normal or low albumin, a normal or reduced phosphate, a raised PTH (or inappropriately in the normal range), and a normal urea. PTH should be suppressed by high calcium concentration due to any other cause. The exception is familial benign hypercalcaemia where PTH may be normal or elevated but when, unlike other causes, the calcium excretion index (CEI) is low despite high plasma calcium. ( CEI = [Ca] urine * [creat.] plasma / [creat.] urine)
- other biochemical indications:
- raised albumin + raised urea - implies dehydration
- raised albumin + normal urea - implies a cuffed sample
- normal or low albumin + normal or raised phosphate:
- raised alkaline phosphatase - suggests bony metastases, sarcoidosis, or thyrotoxicosis
- normal alkaline phosphatase - myeloma (raised plasma protein), vitamin D excess, milk-alkali syndrome, thyrotoxicosis, sarcoidosis
A ten day glucocorticoid suppression test may be diagnostically useful.
- prolonged application of a tourniquet should be avoided when obtaining a blood sample to test serum calcium concentration
- adjusted calcium levels is an approximate value and may be inaccurate in cases of extreme albumin concentrations e.g. - patients with paraproteinemias (1)
Last reviewed 01/2018