Calcium Blood Test

A calcium blood test measures the amount of calcium in your blood. Too much or too little calcium in your blood may be a sign of a wide range of medical conditions, such as bone disease, thyroid disease, parathyroid disorders, kidney disease, and other conditions. Calcium is one of the most important minerals in your body.

About 1% of the calcium in your body is in your blood. The rest is stored in your bones and teeth. Having the right amount of calcium in your blood is necessary for your nerves, muscles, and heart to work properly.

It also helps blood vessels move blood throughout your body and helps release hormones that affect many body functions.

Why this test is done

Your health care provider may have ordered a basic or comprehensive metabolic panel, which includes a calcium blood test, as part of your routine checkup. You may also have this test to diagnose or monitor conditions that can affect your blood calcium or if you have symptoms of abnormal calcium levels.

Symptoms of high calcium levels may include:

• Digestive symptoms, such as:
• Constipation
• Nausea and vomiting
• Abdominal (belly) pain
• Loss of appetite
• Increased thirst
• Urinating (peeing) more than usual
• Kidney stones
• Bone, joint, and muscle symptoms, such as weakness, aches, and pains
• Fatigue
• A change in mental health, such as depression or confusion

Symptoms of low calcium levels may include:

• Dry skin, coarse hair, and nails that easily break (after a long period of low levels)
• Muscle cramps, spasms, or stiffness
• Tingling in the lips, tongue, fingers, and feet
• Irregular heartbeat (arrhythmia)
• Seizures, if calcium levels are extremely low

Many people with high or low calcium levels don't have any symptoms. So your provider may order a calcium test if you have a known condition that may affect your calcium levels, such as:

• Kidney disease
• Thyroid or parathyroid disease
• Malnutrition
• Problems absorbing calcium
• Certain types of cancer

How to prepare

You usually don't need any special preparations for a calcium blood test or a basic or comprehensive metabolic panel. You may need to stop taking certain medicines or supplements, such as vitamin D, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.

If your provider has ordered more tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if there are any special instructions to follow.

Sample type

Blood

Other names for this test

total calcium, ionized calcium