Serum myoglobin is a blood test used to determine muscle damage, including muscle damage to the heart such as occurs after a heart attack. Elevated serum myoglobin may also indicate skeletal muscle damage or a variety of other conditions.

The test measures the level of myoglobin found in a person’s serum (the liquid part of blood that has had the clotting elements removed). Myoglobin is a protein that is found in heart muscles and skeletal muscles throughout the body. When a muscle is damaged, myoglobin is released into the blood. Eventually, the substance is eliminated from the body through urine.

Normal myoglobin levels range from 0 to 85 nanograms per milliliter (ng/ml). Higher serum myoglobin levels mean that the patient has severe muscle damage somewhere in the body. This test has been largely replaced by other tests, such as those for cardiac enzymes.

Serum myoglobin is a blood test that measures the amount of myoglobin found in a person’s serum (the liquid part of blood that has had the clotting elements removed). Myoglobin is an oxygen-storing protein found in muscles throughout the body, including the heart.

Myoglobin is important because it acts as a reservoir of oxygen for muscles that are working. By releasing its extra oxygen at moments of peak stress, myoglobin allows muscles to continue working longer at a higher level than might otherwise be possible. However, damaged muscles lose their oxygen-storing myoglobin as it spills out into the blood. Therefore, testing for myoglobin levels in either the blood or the urine is a good strategy for screening for muscle damage.

Serum myoglobin levels are used to:

Normal serum myoglobin levels range from 0 to 85 nanograms per milliliter (ng/ml). Because only trace amounts of myoglobin are found in normal blood, a normal blood test result may be reported simply as “negative.” High serum myoglobin levels could mean that the heart muscle has been severely damaged from a heart attack. Myoglobin levels will also rise after an injury has severely damaged skeletal muscles or when polymyositis worsens.

Serum myoglobin testing has certain advantages over the other serum marker tests that physicians use to diagnose a heart attack. Normally, physicians rely on three conditions to diagnose a heart attack:

• Chest pain
• Electrocardiogram (EKG) results
• Elevated serum markers such as creatine kinase and cardiac troponin

The drawback to this traditional approach is that not all Chest pain and abnormal EKG results are related to heart attack, and the traditional blood serum markers often take hours to become elevated.

By contrast, myoglobin levels have been shown to rise quickly after a heart attack – sometimes as rapidly as 90 minutes – making it possible to diagnose heart attack more quickly. However, serum myoglobin testing alone is not enough to give a definitive diagnosis.

There are two reasons for this. First, during a heart attack, myoglobin is released in “waves,” meaning that levels rise and fall unpredictably, leading the confusion. Second, myoglobin is not specific to the heart. An elevated level might indicate of a number of noncardiac factors. Because of these drawbacks, serum myoglobin testing is not a standard part of the battery of tests when a heart attack is suspected. However, some studies have shown that when serum myoglobin is measured in conjunction with the other traditional serum markers, physicians are sometimes able to positively diagnose a heart attack more quickly.

Serum myoglobin is generally used as a diagnostic tool. Therefore, most patients will not require regular testing.

Restriction in diet or medications are generally not required prior to serum myoglobin testing but there are several factors that may affect the accuracy of the test. These include:

There is no such thing as an abnormally low serum myoglobin level because zero nanograms per milliliter (ng/ml) is within the range of normal. An abnormally high serum myoglobin level indicates muscle damage within the body. Because significant damage is needed to release myoglobin in the blood, these abnormal levels usually indicate a severe condition, such as the following:

Though myoglobin is an important source of oxygen for active muscles, recent research has suggested that myoglobin is not necessary for survival. Laboratory-altered animals that could not produce myoglobin were still able to exercise, reproduce and thrive as well as their myoglobin-making counterparts. The only difference found was in the color of the animal’s muscles.

Myoglobin is a pigment. It alters the color of the tissues in which it is present. In fact, myoglobin is the reason that “white” meat is lighter in color than “red” or “dark” meat. Muscles that are actively used hold more myoglobin. Cattle are more active animals than pigs, making beef a red meat and pork a white meat. In chickens and turkeys, the active legs are dark meat, while the unused breasts are white meat. Birds that use their breast muscles to fly, such as ducks or pheasant, have dark meat throughout their bodies.

Fish are the exception. Although all their muscles are active, they use very little myoglobin because they have a faster method of getting extra oxygen to their muscles. Most fish, therefore, consist only of white meat.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to serum myoglobin:

1. Why should I have a serum myoglobin test?
   
   
2. Are there any risks associated with this test?
   
   
3. What type of results would you expect to see from this test?
   
   
4. What type of results would you consider abnormal?
   
   
5. Do I need to make any advanced preparations in order to take this test?
   
   
6. Where can I have the test done?
   
   
7. When and from whom will I receive the results of my test?
   
   
8. Do my test results indicate any damage to my heart?
   
   
9. Could other factors have affected my test results?
   
   
10. Will I need any additional tests for you to make a diagnosis?
    
    
11. How often will I need to have this test?