Creatine kinase (CK) is an enzyme (a molecule that helps speed up certain chemical reactions) that occurs naturally inside muscle cells throughout your body. Different forms of CK occur in different places, and most of the myocardial band (MB) version of this enzyme occurs in muscle cells in your heart.
Damage to heart muscle cells causes CK-MB — as well as several other proteins and enzymes — to leak into your blood. This test can detect how much CK-MB enzyme is in your blood. If there’s more CK-MB in your blood than there should be, it can be a sign you’ve had a heart attack.
CK-MB is also a time-sensitive test. The level of CK-MB in your blood will rise sharply after a heart attack and then return to normal after two or three days.
Advertisement
CK-MB can be found in heart muscle, making it useful for detecting any kind of injury to your heart. However, other muscles also contain CK-MB, which is why tests for cardiac troponin (which is specific to your heart) are now the tests of choice.
Because it’s useful for diagnosing heart attacks, which are life-threatening medical emergencies, a hospital emergency room is where most CK-MB tests happen. However, you might also undergo a CK-MB test when you’re a patient in a hospital if your healthcare provider suspects a heart attack or other injury to your heart.
Advertisement
CK-MB testing involves several medical professionals. This usually (but not always) includes the following:
Because heart attacks aren’t predictable, it usually isn’t possible to prepare for this test.
Important: If you take Vitamin B7, also known as biotin, tell your provider about this as soon as possible before they take a blood sample. Biotin can interfere with the test results, which is important information for your provider to have as they care for you. Depending on what dose of biotin you take and when you last took it, you may need to wait to give a blood sample for this test (this doesn’t apply to tests in urgent or emergency situations).
The test starts with a phlebotomist who will draw blood from a vein, usually one in your arm or hand. If you already have an intravenous line inserted into a vein, they may be able to get the sample from that line.
Depending on the testing technology available, some labs can run this test in less than 20 minutes. The provider who ordered the test will review the results and discuss them with you.
It’s common for providers to order repeats of this test (this is called serial testing) to track your CK-MB levels over time. Having a timeline of results can sometimes help rule out a heart attack. However, repeating the test may change when your provider discusses your results with you.
The most common side effects of this test, if the sample came directly from a vein and not from an IV line, are mild bruising or soreness.