Methylene blue test
The methylene blue test is a test to determine the type of methemoglobinemia, a blood disorder.
How the Test is Performed
The health care provider wraps a tight band or blood pressure cuff around your upper arm. The pressure causes veins below the area to fill with blood.
The arm is cleaned with a germ killer (antiseptic). A needle is placed into your vein, usually near the inside of the elbow or back of the hand. A thin tube, called a catheter, is placed into the vein. (This may be called an IV, which means intravenous). While the tube stays in place, the needle and tourniquet are removed.
How to Prepare for the Test
No special preparation is required for this test.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
Why the Test is Performed
There are several types of oxygen-carrying proteins in the blood. One of them is methemoglobin. Normal methemoglobin level in blood are usually 1%. If the level is higher, you can become sick because the protein is not carrying oxygen. This can make your blood look brown instead of red.
Methemoglobinemia has several causes, many of which are genetic (problem with your genes). This test is used to tell the difference between methemoglobinemia caused by the lack of a protein called cytochrome b5 reductase and other types that are passed down through families (inherited). Your doctor will use the results of this test to help determine your treatment.
Normally, methylene blue quickly lowers the level of methemoglobin in the blood.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
You may have a rare form of methemoglobinemia if this test does not significantly lower blood levels of methemoglobin.
Veins and arteries vary in size from one person to another and from one side of the body to the other. Inserting an IV may be more difficult for you or your child than for other people.
Other risks associated with this type of blood test are minor, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin causing bruising)
- Infection (a slight risk any time the skin is broken, but the chances of infection increase the longer the IV remains in the vein)
DeBaun MR. Hemoglobinopathies. In: Kliegman RM, Stanton BF, St. Geme J III, Schor N, Behrman RE, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 456.
Reviewed By: Chad Haldeman-Englert, MD, FACMG, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.