Urine myoglobin is a test to detect the presence of myoglobin in a sample of urine.

Myoglobin is a protein in heart and skeletal muscles. When a muscle is exercised, it uses up available oxygen. Myoglobin has oxygen attached to it, which provides extra oxygen for the muscle to maintain a high level of activity for a longer period of time.

When muscle is damaged, the myoglobin in muscle cells is released into the bloodstream. The kidneys help remove myoglobin out of the body. In large amounts, myoglobin can damage the kidney and break down into toxic compounds, causing kidney failure.

A clean-catch (midstream) urine sample is needed.

Men or boys should first wipe clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well.

As you start to urinate, allow a small amount to fall into the toilet bowl (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. Give the container to the health care provider or assistant.

In infants, thoroughly wash the area where urine exits the body. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For boys, place the entire penis in the bag and attach the adhesive to the skin. For girls, place the bag over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts -- lively infants can move the bag, causing the urine to be absorbed by the diaper. Check the infant frequently and change the bag after the infant has urinated into it. Drain the urine from the bag into the container provided by your health care provider.

Deliver it to the laboratory or your health care provider as soon as possible upon completion.

The test involves only normal urination, which should cause no discomfort.

Myoglobin levels may be obtained when muscle damage, including skeletal and heart muscle damage, is suspected.

A normal urine sample does not have myoglobin. Sometimes a normal result is reported as negative.

The presence of myoglobin in the urine may indicate:

• Skeletal muscle ischemia (blood deficiency)
• Skeletal muscle trauma
• Skeletal muscle inflammation (myositis)
• Heart attack
• Muscular dystrophy
• Rhabdomyolysis
• Malignant hyperthermia (very rare)

There are no risks.

Barohn RJ. Muscle diseases. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 447.

O’Connor FG, Deuster PA. Rhabdomyolysis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 114.