Serum or plasma mass concentration of calcium (total)

This blood test measures the amount of calcium in your blood. Your doctor may order it to check your bone health, kidney function, nerve signaling, and muscle movement, or to help investigate symptoms such as fatigue, weakness, numbness, tingling, or an irregular heartbeat.

Doctors may order this test to check for conditions like low or high calcium levels, which can affect your bones, heart, muscles, or nerves. It might also be done if you have symptoms such as muscle spasms, confusion, or abnormal heart rhythms.

Before the test, ask your doctor whether you need to fast, since some calcium tests require avoiding food and drinks for several hours. Tell your care team about all medicines, vitamins, and supplements you take, especially calcium supplements, antacids, diuretics, or thyroid medicines, because these can change your results. Drink water unless you are told otherwise, and try to arrive relaxed.

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it involves a blood draw, but this depends on your healthcare provider’s instructions.

During the test, a nurse or phlebotomist will wrap a band around your upper arm, clean the skin, and draw a small sample of blood from a vein, usually on the inside of your elbow. You may feel a brief pinch or sting, but the procedure typically takes only a few minutes. Afterward, a small bandage is placed over the site, and you can return to your normal activities right away.

A healthcare professional will draw blood from a vein in your arm. The sample is then sent to a lab for analysis using an automated method to measure total calcium levels.

Results are usually reported in milligrams per deciliter (mg/dL). A typical normal range for total calcium in adults is about 8.5 to 10.2 mg/dL, though each laboratory sets its own reference range. Higher than normal results, called hypercalcemia, may suggest overactive parathyroid glands or certain illnesses, while lower results, called hypocalcemia, may point to vitamin D deficiency, kidney disease, or low parathyroid activity. Your doctor will interpret your numbers together with your symptoms and other lab work.

Results are reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). Your results will be compared to standard reference ranges provided by your lab.