Patient education: Calcium blood test (The Basics)

What is a calcium test? — A calcium test is a type of blood test. It measures the amount of calcium in the blood.

Calcium is a mineral. The body needs it for the bones, muscles, and heart to be healthy. Most of the body's calcium is stored in the bones and teeth. But calcium is also in blood. Some of this calcium is "bound," meaning it attaches to proteins in the blood. The rest is called "ionized" or "free."

Blood tests can measure:

●Total calcium – This measures all calcium in the blood. This is the most common test used to check a person's calcium level.

●Ionized calcium – This measures ionized (free) calcium only. It might be done if a total calcium test shows abnormal results, or if a person has certain symptoms or health conditions.

Different health problems can affect the blood calcium level. These include:

●Problems with the parathyroid glands or kidneys

●Certain types of cancer

●Having too much or too little vitamin D

●Certain medicines

Calcium is usually measured as part of a "metabolic panel." This is a blood test that measures the total calcium as well as other substances in the blood.

Why might I need a calcium test? — Your doctor might want you to get a calcium test if:

●You have symptoms of low calcium – The medical term for this is "hypocalcemia." Symptoms can include muscle cramps or spasms, seizures, dry skin, or mood changes.

●You have symptoms of high calcium – The medical term for this is "hypercalcemia." Symptoms can include urinating a lot, feeling very thirsty, lack of appetite, nausea, constipation, weakness, or trouble concentrating.

●You have a known health condition or take a medicine that affects your calcium levels.

How do I prepare for a calcium test? — For this test, you need to get a "blood draw." Your doctor or nurse will tell you where to go for this. You don't need to "fast" (avoid eating or drinking) before this test. But if you are having other tests on the same day, your doctor or nurse might tell you to fast before those tests.

It might help to wear a short-sleeve shirt to your blood draw appointment. This makes it easier for the person drawing your blood to get to your arm.

What happens during a blood draw? — For the blood draw, a needle is used to take a small amount of blood from your arm (figure 1). Collecting the blood only takes a few minutes. The blood is then tested in a lab.

Tell the person who takes your blood:

●If you take "blood thinner" medicines or if you have a bleeding problem – They will make sure that your bleeding is under control before you leave.

●If you have a latex allergy – Some of the supplies used for blood draws might contain latex.

●If you have a preferred arm to use

Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in.

What do my results mean? — Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.

If your calcium level is too low or too high, your doctor or nurse will talk to you about what to do next. They might need to do more tests to figure out what the cause is.

If you do have a health problem, your doctor will work with you to come up with a plan for treatment.

More on this topic

Patient education: Basic metabolic panel (The Basics)
Patient education: Comprehensive metabolic panel (The Basics)
Patient education: Hypercalcemia (The Basics)
Patient education: Primary hyperparathyroidism (The Basics)
Patient education: Hypoparathyroidism (The Basics)
Patient education: Calcium and vitamin D for bone health (The Basics)
Patient education: Bone problems caused by kidney disease (The Basics)
Patient education: Vitamin D deficiency (The Basics)

Patient education: Primary hyperparathyroidism (Beyond the Basics)
Patient education: Calcium and vitamin D for bone health (Beyond the Basics)
Patient education: Vitamin D deficiency (Beyond the Basics)