Calcium in men: what your level means, causes and medication

This test measures total calcium in the blood, expressed in millimoles per litre (mmol/l). Proteins, chiefly albumin, carry some 45 percent of that calcium, another 45 percent is free, ionised calcium, the active form, and the remaining 10 percent is attached to other small molecules.

For adults aged 19 and over, the NUMBER study, which pooled 7.6 million results from Dutch GP practices, gives 2.18 to 2.55 mmol/l as the reference range. The NVKC, the Dutch society for clinical chemistry, gives 2.10 to 2.55 mmol/l, and 1.15 to 1.33 mmol/l for free calcium in venous blood. The laboratory that runs this test prints 2.15 to 2.55 mmol/l on your report. Reference values therefore differ per source and per laboratory, and the limits on your own report take precedence.

Your body keeps this value within tight limits; parathyroid hormone (PTH) and vitamin D do that together, and to hold the blood level steady the body draws calcium from bone when needed. That is why a normal result says nothing about your bone density.

When albumin is low, total calcium reads lower while free calcium can be normal. Labs sometimes correct for this with a formula, but it often misclassifies people, especially when albumin is below 30 g/l; free calcium is then the better measurement.

A high level is called hypercalcaemia, and an overactive parathyroid gland or cancer explains about 90 percent of cases. A high result is therefore no diagnosis on its own, because there are other causes, and three of them are common medicines or supplements: a thiazide, a diuretic prescribed for high blood pressure, can raise calcium, too much calcium carbonate or other antacids for heartburn can do the same, and so can too much vitamin D.

Excess calcium can show up as thirst and frequent urination, and kidney stones are another possible signal. Lithium, sarcoidosis, an overactive thyroid and long periods of immobility are also listed as causes, as is reduced kidney function, measured with creatinine.

A normal value is no verdict on your bones. The body keeps the blood level steady by drawing on bone when it needs to, so strength training or bone loss does not show up in this number; bone density is assessed with a DEXA scan. In men, low testosterone is associated with lower bone density, and the Endocrine Society testosterone guideline from 2018 lists low bone density among its possible signs. Discuss any worry about your bones with your GP, because a calcium test cannot answer it.

A low level is called hypocalcaemia. Possible causes include a shortage of vitamin D or magnesium, kidney failure and alcohol, and proton pump inhibitors for reflux can also lower calcium. A low albumin makes total calcium look lower than the free calcium really is.

Consider a calcium test if you have complaints that fit a high level, such as thirst, frequent urination, tiredness, constipation or abdominal pain, or a history of kidney stones. The same goes for tingling around the mouth or muscle cramps, which can come with a low level. If you take a thiazide for blood pressure, lithium or a reflux medicine, or take vitamin D or calcium carbonate antacids on your own, a test shows where your calcium currently stands.

A doctor reads an abnormal result alongside albumin, PTH, vitamin D, kidney function, phosphate and magnesium. The complete metabolic panel measures calcium together with albumin and creatinine, and a result that stays abnormal is a reason to see your GP. The tourniquet matters at the draw: prolonged stasis can raise measured calcium, although within about a minute the effect is negligible, and your posture shifts the value slightly as well.

You order the test online, without a GP referral. You give blood at a partner location, part of a network of independent, certified laboratories, the result follows within about 120 hours, and a BIG-registered doctor assesses every result.