What to Know About Myoglobin

Medically Reviewed by James Beckerman, MD, FACC on June 29, 2023
4 min read

‌Your body is a complex system of bones, skin, organs, chemicals, and more. Among the chemicals are special proteins known as hemeproteins (or hemoproteins), which are made of amino acids and iron

You can find these proteins in the muscles and blood, where they bind with oxygen. The proteins in your blood are called hemoglobin. The proteins in your muscles are called myoglobin. 

‌Myoglobin has several roles, but its most important role is to act as storage for oxygen. This protein attaches to oxygen in the blood and takes it to the muscles throughout your body, especially your heart and skeletal muscles. Once there, myoglobin finds a resting spot and stores the oxygen until you need it. ‌‌

The more active you are, the more oxygen your muscles use. For example, if you do a lot of exercising or sports activities, your muscles may use up more of their oxygen. This can leave your muscles tired and sore. 

But you don’t need to do intense physical activity to use up oxygen in your muscles. Even regular body movements such as bending, lifting, or walking need some oxygen.

‌Myoglobin helps your muscles stay oxygenated by releasing stored oxygen into the muscle fibers. This also helps the muscles contract and relax. ‌‌

This protein also acts like an enzyme when it helps break down nitric acid and turn it into nitrate. By doing so, myoglobin helps the mitochondria inside cells — the small structures that take in nutrients — get full access to oxygen.

‌Healthy myoglobin levels in your blood could range from 25 to 70 micrograms per liter. There will always be a small amount of myoglobin in your bloodstream as it brings oxygen to your muscles. Myoglobin has to link up with oxygen in the bloodstream; it can’t get oxygen from anywhere else.‌‌

Under normal conditions, the small amount of myoglobin in your blood makes its way to your kidneys. Here, your kidneys break down the protein and pass it into your urine for removal. 

‌There shouldn’t be too much myoglobin in your blood. If there is a lot, it’s a sign that your muscles are damaged. Because damaged muscles can’t hold onto myoglobin, they can’t stop it from leaking into your bloodstream. High amounts of myoglobin in your blood could even harm your kidneys and lead to kidney disease. ‌

‌Normally, the amount of myoglobin in your urine is so minimal that lab tests often can’t measure it. This means you might have too much myoglobin in your urine — a term called myoglobinuria — if a lab test can easily detect it. 

‌‌Several factors can lead to higher amounts of myoglobin in your blood or urine.‌‌

Rhabdomyolysis. Rhabdomyolysis is a condition that causes muscle damage and muscle death. You could get this life-threatening condition from certain medications, alcohol, and drugs, extreme amounts of fitness, infections, or trauma from an accident.‌

Severe muscle injury. If you seriously injure a part of your body, the affected muscles often release myoglobin into the blood. This release of myoglobin can show up in your urine as well. ‌

Heart attack. A sudden increase in myoglobin can point to a heart attack that injured the heart muscle. ‌

Malignant hyperthermia. This condition is most often a severe reaction to anesthetics and muscle relaxants. It can also happen if your body gets very heat stressed. Some of the symptoms of this condition, called malignant hyperthermia, include muscle spasms and muscle rigidity.‌

Muscular dystrophy. Muscular dystrophy is a group of diseases that leads to muscle weakness. This weakness can happen in some of your muscles but not others, and it can range from mild to severe.  ‌

Myositis. Myositis is the name for a group of diseases with inflammation in the skeletal muscle. This inflammation causes muscle damage as well.

‌‌If you’re showing specific signs and symptoms, your doctor might be concerned about myoglobin in your blood and urine. They’ll likely want you to get one or two different myoglobin tests.‌‌

Myoglobin blood test. Also called a serum myoglobin, this test measures how much myoglobin you have in your blood. You can get higher amounts of myoglobin in your blood two to three hours after the muscle damage happens. The highest amounts happen about eight to 12 hours later.‌‌

Myoglobin urine test. This test checks to see if your urine has myoglobin in it. Myoglobin in your urine can cause kidney damage and may even lead to kidney failure. Depending on the results, your doctor might want you to get intravenous (IV) fluids or other treatments.‌‌

If you feel unwell, don't hesitate to speak to your doctor. The sooner you get these important tests, the sooner you can begin treatment.