A blood sample is needed.

No special preparation is necessary.

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.

Hemoglobin transports oxygen. RBCs carry hemoglobin and oxygen to our body's cells. The RBC indices test measures the size and hemoglobin of the RBCs. 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.

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 vitamin B12 levels, or chemotherapy) or liver disease.
• 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 vitamin B12 levels, or chemotherapy or liver disease).

There is little risk involved with having your blood taken. 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
• Multiple punctures to locate veins
• Hematoma (blood buildup under the skin)
• Infection (a slight risk any time the skin is broken)

Erythrocyte indices; Blood indices; Mean corpuscular hemoglobin (MCH); Mean corpuscular hemoglobin concentration (MCHC); Mean corpuscular volume (MCV); Red blood cell indices

Elghetany MT, Banki K. Erythrocytic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 33.

Means RT Jr. Approach to the anemias. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 144.

Thom CS, Lambert MP. Blood disorders. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 138.

Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 31.

Updated by: Frank D. Brodkey, MD, FCCM, Associate Professor, Section of Pulmonary and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.