Calcium is an essential mineral your body needs to build strong bones and teeth. It also helps nerves fire and transmit information correctly and plays a vital role in heart function, muscle contraction, and blood clotting. Calcium is available as a dietary supplement, but foods such as milk and kale are also rich in the mineral.
A calcium blood test measures the total amount of calcium in your blood. Results of the blood test can show if you have too much or too little calcium in your blood. Irregular calcium blood levels rarely present any unusual signs or symptoms, so a calcium blood test may be the only way to detect a potential problem.
A calcium blood test can be part of a screen for a variety of diseases and conditions, including osteoporosis, cancer, and kidney diseases. This blood test may also be required to monitor ongoing treatments of other conditions, or to check that any medications you are taking don’t have any unintended side effects.
Your doctor may order this test if he or she suspects any of the following conditions:
- bone diseases, such as osteoporosis or osteopenia
- chronic kidney or liver disease
- disorders of the parathyroid gland
- malabsorption or a disorder that affects how your body absorbs nutrients
- an over or underactive thyroid gland
During the calcium blood test, a nurse or healthcare technician will draw blood from a vein—typically from the inside of the elbow or the back of your hand. A nurse in your doctor’s office may also draw blood while you’re already in the office for a regular checkup. If not, you may be sent to a nearby lab or hospital to have your blood drawn.
If you are currently taking any prescription or over-the-counter medicines, vitamins, or supplements, let your doctor know. Your doctor may instruct you to stop taking a medicine that can interfere with the blood test or cause an unusually high or low reading.
The blood draw site will first be cleaned with an antiseptic wipe. Then, the nurse will wrap an elastic band around your upper arm to increase pressure in the area and help the veins swell with blood so that your veins are easier to see. The elastic band may be uncomfortable at first, but it will be removed shortly.
The nurse or technician will prick your vein with a needle. You may feel a slight sting when this is done, but having your blood drawn is relatively painless. The blood flows through the hollow needle into a vial or tube. Once blood flow is established, the elastic band will be removed. When enough blood has been collected, the needle is removed and you will need to apply pressure to the puncture site to stop any bleeding.
Higher or lower-than-normal results may signal any number of conditions, including:
- excessive vitamin D intake
- hyper or hypoparathyroidism
- kidney stones
- HIV or AIDS
- liver disease
- neurologic disorders
Without this blood test, these conditions could go undiagnosed and begin to cause bigger problems.
High or low calcium levels present very few real problems until the calcium numbers are so high or so low that you begin showing signs, such as:
- muscle cramps
- muscle spasms
The risks associated with having your blood drawn are very rare. They include:
- bleeding at the puncture site, or a hematoma (blood collecting under the skin)
- bruising around the puncture site
- fainting or feeling light-headed after having blood drawn
- infection at the puncture site
Your blood sample will be sent to a laboratory for analysis. Your doctor’s office will be notified of your results in a few days, and they should contact you to discuss the findings. If you have not heard from your doctor’s office within a week of your blood draw, call the office and ask for an update.
Normal calcium blood levels are between 8.5 and 10.2 mg/dL. However, normal value ranges vary slightly among laboratories and doctors’ offices. Ask your doctor to explain your reading and what should be done if you have an abnormal reading.