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Calcium (Blood)

Does this test have other names?

Total calcium, ionized calcium

What is this test?

A calcium blood test measures how much calcium is in your blood. Your healthcare provider can use this test to help diagnose and watch many conditions. There are two types of calcium blood tests. One is total calcium and the other is ionized calcium. Ionized calcium measures the "free" calcium in your blood. This is the calcium not bound to other parts of the blood. 

Why do I need this test?

Your healthcare provider may order a calcium blood test to help diagnose a variety of disorders. These include kidney disease, pancreatitis, and disease of the parathyroid gland. Calcium levels may also be abnormal in many types of cancer. Your provider might also order this test as part of a routine health check.

A normal calcium level in the blood is a good sign that your body is likely working as it should. Calcium levels that are too low (hypocalcemia) or too high (hypercalcemia) can mean of a number of problems.

People with abnormal calcium levels may not have any symptoms. Very low calcium levels can cause seizures, irregular heartbeat, muscle spasms, or tingling in the hands or feet. People with high calcium levels may have nausea, vomiting, severe thirst, or constipation. Your healthcare provider will use the results of a blood calcium test to figure out how to treat the underlying cause of any health problems you may have.

What other tests might I have along with this test?

Calcium can be tested for a number of reasons. Other tests will vary based on what your healthcare provider is looking for. 

Your provider may also order tests of kidney function, vitamin D, phosphorus levels, and parathyroid hormone. These tests can help figure out what is causing your abnormal calcium levels.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Some laboratories may have slightly different normal values than the ones below. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.

A normal range of total blood calcium in adults is usually between 8.5 and 10.3 milligrams/deciliter (mg/dL). Ionized calcium generally should be higher than 4.6 mg/dL to be a normal level. 

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

A number of things can affect the results of a calcium blood test. This test is typically done at the same time as other blood tests to get a better picture of your overall health. Certain medicines can change blood calcium levels and affect the test results. 

How do I get ready for this test?

You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.  

Medical Reviewers:

  • Snyder, Mandy, APRN
  • Taylor, Wanda L, RN, PhD