Methylmalonic acid

Definition

This is a blood test that measures the amount of methylmalonic acid.

How the test is performed

Blood is drawn from a vein on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

The blood is then sent to the laboratory for analysis.

How to prepare for the test

No special preparation is necessary.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test is used to look for methylmalonic acid in the blood. Elevated levels of this chemical occurs in certain genetic disorders and vitamin B-12 deficiency.

Normal Values

Normal serum methylmalonic acid levels are 0.08 to 0.56 micromoles/L. Values higher than this may mean vitamin B-12 deficiency or a genetic disease resulting in high levels of methylmalonic acid (methylmalonic acidemia).

What abnormal results mean

• possible methylmalonic acidemia because of a genetic disease
• vitamin B-12 deficiency

What the risks are

The risks associated with having blood drawn are:

• excessive bleeding
• fainting or feeling light-headed
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Illustrations

Blood test