Enzyme Markers

An enzyme marker is a blood test to measure enzymes, proteins in your blood that can indicate tissue damage or disease. Elevated cardiac enzymes after a heart attack are a sign of serious heart damage. High levels of CPK isoenzymes may indicate a muscle disease, while elevated liver enzymes suggest liver damage.


What are enzyme markers?

An enzyme marker is a blood test to measure the levels of specific enzymes in your blood. Musculoskeletal diseases, organ damage and injuries can cause enzymes to leak from cells into your blood.

Your healthcare provider may refer to enzyme markers as biomarkers (biological markers). A biomarker is a measurable indicator (medical sign) of a disease.


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What are enzymes?

Enzymes are proteins that aid chemical changes in your body and speed up metabolism. Your body has thousands of enzymes that perform unique functions. Enzymes play important roles in the:

Who needs an enzyme marker test?

Healthcare providers use enzyme marker tests for different purposes:

  • Screenings: As part of a routine physical examination, an enzyme marker test can identify potential problems like organ or muscle damage or stress.
  • Diagnosis: You may get an enzyme marker test to diagnose a specific disease or heart problem.
  • Monitoring: Test results can show if a treatment is working or if medications are damaging organs.


What are the types of enzyme marker tests?

Healthcare providers use different enzyme marker tests to check for diseases and disease progression. Enzyme marker tests include:

  • Cardiac enzyme test.
  • Creatinine phosphokinase (CPK) isoenzymes or creatine kinase test, including CK-MB, CK-MM, and CK MM.
  • Liver enzyme test (ALT, AST, Alkaline phosphatase, GGT, 5’-NT).

What is a cardiac enzyme test?

A cardiac enzyme test checks for signs of heart muscle damage following a heart attack or another heart problem. It can also assess heart function after surgeries like coronary artery bypass grafting (CABG) or angioplasty.

Injury or damage to the heart causes it to release protein called troponin (cTn) and creatinine phosphokinase (CPK). CPK levels rise quickly after a heart attack or injury and were once used to diagnose heart attack. Now, if you’re receiving medical care for a possible heart attack, your healthcare provider will likely use troponin tests to help confirm the diagnosis. Elevated CPK levels may also indicate coronary artery disease. This condition clogs arteries, increasing your risk of a heart attack.

The heart is the only organ that has troponin enzymes. It can take up to 12 hours for troponin levels to increase after a heart attack. Because enzyme levels change after a heart attack, you may get several cardiac enzyme tests spaced several hours apart to measure CPK and troponin levels.

Blood levels of troponin are typically low — around 0.02 nanograms per milliliter (ng/mL). Elevated cardiac enzymes indicate a heart attack. A higher number is a sign of more severe heart damage.

Your healthcare provider may order a cardiac enzyme test if you have symptoms of a heart problem like:

What is a CPK isoenzymes test?

A CPK isoenzymes test looks for elevated CPK levels that indicate tissue damage. Your muscles (including heart muscle), brain and lungs release CPK isoenzymes when there’s tissue damage from a disease or injury. Isoenzymes are forms of the enzyme that are specific to certain organs or tissues. The form of CK that’s specific to the heart is known as CK-MB. The form of CK that’s specific to skeletal muscle is known as CK-MM. CK when used on its own refers to the total amount of CK from all sources.

Depending on your symptoms, diagnosis or disease risk factors, your healthcare provider may order a CPK isoenzymes test to check for conditions like:

What is a liver enzyme test?

Damage to your liver from diseases or an injury causes it to release different enzymes into your bloodstream. The two most common enzymes are alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Your liver primarily makes ALT. Your liver, heart, kidneys, brain and muscles make AST.

A liver enzyme test checks for elevated liver enzymes, which may indicate:

Test Details

How should I prepare for an enzyme marker test?

If you know you’ll be getting a blood draw, these steps can help the process go smoothly:

  • Stay hydrated: Drink lots of water before the test to help your blood flow easier through blood vessels.
  • Avoid nicotine: Don’t smoke (including vaping) because nicotine constricts blood vessels. It’s more difficult to get blood out of a narrow vein.
  • Speak up: Tell your healthcare provider if you have a fear of needles (trypanophobia) or a fear of blood (hemophobia). They can take steps to make the blood draw easier for you.

Should you fast before an enzyme marker test?

Your healthcare provider will let you know if you need to fast (not eat or drink anything except water) before getting an enzyme marker test. Fasting is rarely necessary. Cardiac enzyme marker tests often take place after a heart attack or heart procedure, so you wouldn’t be expected to fast.


What happens during an enzyme marker test?

An enzyme marker test is a simple blood draw. Depending on the situation, the test may take place in your healthcare provider’s office, a blood-testing lab or a hospital. A phlebotomist (a specialist trained in drawing blood) or another healthcare provider draws your blood. The procedure takes only a few minutes.

What should I expect after an enzyme marker test?

You should leave the bandage on for two to four hours to lower the risk of infection. You may experience slight inflammation (swelling) or bruising at the needle site. These issues should clear up in a few days.

These steps can minimize bruising or discomfort:

  • Wrap an icepack in a washcloth and place it on top of the bandaged area.
  • Take an over-the-counter pain reliever.
  • Don’t lift anything heavy or vigorously exercise for 24 hours after the blood draw.

What are the risks of an enzyme marker test?

Blood tests are relatively low-risk procedures. Some people experience a drop in blood pressure during a blood draw. This low blood pressure (hypotension) can make you feel dizzy or nauseated. Tell your healthcare provider immediately if you start feeling unwell or like you’re going to faint. Your healthcare provider can take steps, like reclining you backward, to help the process go smoothly.

Results and Follow-Up

When will I get the test results?

Results come back quickly in an emergency, such as a suspected heart attack. Otherwise, it may take several days for your healthcare provider to get the results back from a lab.

Your healthcare provider will review the results with you. You’ll most likely need additional tests to diagnose or rule out a problem. Depending on the issue, you may get several enzyme marker tests over a few hours or days.

What should I ask my healthcare provider?

You may want to ask your healthcare provider:

  • Why do I need an enzyme marker test?
  • Do I need to fast, stop smoking or stop medicines before I get the test?
  • When will I get the test results?
  • Should I be concerned about the test results?
  • Will I need additional tests?
  • How often do I need an enzyme marker test?

A note from Cleveland Clinic

An enzyme marker test provides important information about organ function, disease progression and treatments. Your healthcare provider may order an enzyme marker test to diagnose or rule out a condition if you’re having certain symptoms. A cardiac enzyme test helps assess heart damage after a heart attack. A CPK isoenzymes test looks for signs of muscle diseases. A liver enzyme test assesses liver function. Your healthcare provider can answer any questions or concerns about this test and its results.

Medically Reviewed

Last reviewed on 11/24/2021.

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