Myoglobin (Blood)

Does this test have other names?

Serum myoglobins, myoglobin-serum

What is this test?

This test measures the amount of a protein called myoglobin in your blood. It's done to help diagnose conditions caused by muscle damage, including heart attack.

Myoglobin is found in your heart and skeletal muscles, where it captures oxygen that muscle cells use for energy. When you have a heart attack or severe muscle damage, myoglobin is released into your blood.

Myoglobin increases in your blood two to three hours after the first symptoms of a heart attack. It usually peaks about eight to 12 hours later. Because myoglobin appears in the blood more rapidly than troponin and other markers of a heart attack, it can help diagnose a heart attack in the earliest stages.

Your kidneys filter your blood for myoglobin so that it can be passed out of your body in your urine. But too much myoglobin can overwhelm your kidneys and lead to kidney failure. In some cases, doctors will use a urine test for myoglobin to help detect the hazard and protect your kidney health.

Why do I need this test?

You may need this test if your doctor suspects you have had a heart attack, which causes damage to the heart muscle. This test is usually done every two to three hours if you enter an emergency room with chest pain or other symptoms of a heart attack.

You may also need this test if you have a severe muscle injury, such as with trauma or a condition that damages muscle. Symptoms of muscle injury or damage include:

• Muscle pain

• Dark-colored urine

• Fever

• Fatigue

• Nausea and vomiting

• Abdominal pain

If your myoglobin level rises too high, you may have to get intravenous fluids or other treatments to help flush the extra myoglobin out of your body. This test will help your doctor find out whether your injuries need treatment right away.

What other tests might I have along with this test?

Your doctor may also order tests to confirm that you've had a heart attack, including:

• Blood tests for other heart attack markers. These tests will look at troponin, creatine kinase, and other substances that may be released when your heart is damaged.

• Electrocardiogram to watch your heart's electrical impulses.

• Imaging tests. Various scans can check your heart for damage, clots, and other problems that may affect its ability to pump your blood.

Your doctor may also order these tests if he or she suspects muscle damage:

• Complete blood count, or CBC, including a differential and platelet count

• Blood urea nitrogen, or BUN; creatinine; and routine electrolytes, including potassium

• Calcium, phosphate, albumin, and uric acid

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. 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 health care provider.

Results are given in micrograms per liter (mcg/L). Normal results are less than 90 mcg/L.

Higher myoglobin levels mean that you may have muscle damage, but they don't show where the damage took place. Your doctor will order other tests to confirm whether you've had a heart attack.

Higher results may also mean muscle damage elsewhere in your body. Muscles can be injured in many ways, including:

• Coma or another situation in which you don't move for a long period of time

• Surgery

• Certain infections

• Poisons and certain medications

• Conditions such as muscular dystrophy

• Unusually strenuous exercise

Higher results may also be caused by:

• Kidney failure

• Shock

• Electrical shock

• Malignant hyperthermia, an inherited condition in which your body temperature rises rapidly and your muscles contract when you have general anesthesia

Lower results may mean you have:

• Rheumatoid arthritis

• Myasthenia gravis

• Antibodies to myoglobin in your blood

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?

Heavy drinking and certain medications can affect your results.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your doctor 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.