How To Prepare

Do not take calcium supplements for 8 to 12 hours before having a blood calcium test. Your doctor will tell you if you should not eat or drink anything before your test.

How It Is Done

The health professional drawing blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Put pressure to the site and then a bandage.

How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

There is very little chance of a problem from having blood sample taken from a vein.

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
• In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin ( Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

A test for calcium in the blood checks the calcium level in the body that is not stored in the bones. Normal values may vary from lab to lab.

Normal

Normal blood calcium values are higher in children because their bones are growing quickly.

An ionized calcium test checks the amount of calcium that is not attached to protein in the blood. The level of ionized calcium in the blood is not affected by the amount of protein in the blood.

High values

• High levels of calcium in the blood may be caused by being on bed rest for a long time, hyperparathyroidism, kidney disease, tuberculosis, or cancer that has spread to the bones. Certain cancers can make a substance that causes high blood calcium levels.
• High levels of calcium in the blood can be caused by eating a diet with too much vitamin D, vitamin A, or calcium. Eating large amounts of milk products or taking too many calcium medicines, such as antacids or vitamin supplements, can also cause high blood calcium levels.
• High levels of calcium in the blood can be caused by dehydration, sarcoidosis, chronic liver or kidney problems, Paget's disease, and Addison's disease.
• In rare cases, hyperthyroidism may cause high blood calcium levels.
• In a person with cancer, a high blood calcium level is an emergency. Treatment must be started immediately to prevent the person from becoming confused and dehydrated.

Low values

• Low levels of calcium in the blood can be caused by parathyroid gland ( hypoparathyroidism) problems, problems with your intestines that stop your body from absorbing calcium and other nutrients from food ( malabsorption syndrome), bone problems, kidney disease, acute pancreatitis, or low amounts of the protein albumin in the blood (hypoalbuminemia).
• Low ionized calcium levels may be caused by low magnesium levels.
• Pregnant women and older men may also have low calcium levels.