Red blood cell (RBC) indices are part of the complete blood count (CBC) test. They are used to help diagnose the cause of anemia, a condition in which there are too few red blood cells.
The indices include:
- Average red blood cell size (MCV)
- Hemoglobin amount per red blood cell (MCH)
- The amount of hemoglobin relative to the size of the cell (hemoglobin concentration) per red blood cell (MCHC)
How the Test is Performed
A blood sample is needed.
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. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
Hemoglobin transports oxygen. RBCs carry hemoglobin and oxygen to our body's cells. The RBC indices test measures how well the RBCs do this. The results are used to diagnose different types of anemia.
These test results are in the normal range:
- MCV: 80 to 100 femtoliter
- MCH: 27 to 31 picograms/cell
- MCHC: 32 to 36 grams/deciliter (g/dL) or 320 to 360 grams per liter (g/L)
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
These test results indicate the type of anemia:
- MCV below normal. Microcytic anemia (may be due to low iron levels, lead poisoning, or thalassemia).
- MCV normal. Normocytic anemia (may be due to sudden blood loss, long-term diseases, kidney failure, aplastic anemia, or man-made heart valves).
- MCV above normal. Macrocytic anemia (may be due to low folate or B12 levels, or chemotherapy).
- MCH below normal. Hypochromic anemia (often due to low iron levels).
- MCH normal. Normochromic anemia (may be due to sudden blood loss, long-term diseases, kidney failure, aplastic anemia, or man-made heart valves).
- MCH above normal. Hyperchromic anemia (may be due to low folate or B12 levels, or chemotherapy).
Veins and arteries vary in size from one person 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.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
This information should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. © 1997- 2007 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.