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Tests and diagnosis
By Mayo Clinic staffDoctors diagnose vitamin deficiency anemias through blood tests that check:
- The level and appearance of red blood cells. In anemia, you have fewer red blood cells. In vitamin deficiency anemias, the red blood cells that you do have are large and underdeveloped. In advanced deficiencies, white blood cells and platelets also look abnormal under a microscope.
- The amount of folate, vitamin B-12 and vitamin C in your blood. Folate and vitamin B-12 levels are measured at the same time, because these deficiencies often coexist.
Additional tests for B-12 deficiency
If blood tests reveal a vitamin deficiency, your doctor may perform other tests to determine the type and cause. Diagnosing vitamin B-12 deficiency in particular may involve more tests, such as:
- Antibodies test. Your doctor may draw a sample of your blood to check for antibodies to intrinsic factor. Their presence indicates pernicious anemia.
- Methylmalonic acid test. You may undergo a blood and urine test to measure the presence of a substance called methylmalonic acid. The level of this substance is higher in people with vitamin B-12 deficiency.
- Schilling test. In this test, you first ingest a tiny amount of radioactive vitamin B-12. Then your blood is checked to see if your body absorbed the vitamin B-12. After that, you ingest a combination of radioactive vitamin B-12 and intrinsic factor. If the radioactive B-12 is absorbed only when taken with intrinsic factor, it confirms that you lack your own intrinsic factor. If your body doesn't absorb vitamin B-12 with or without intrinsic factor, you likely have a more general absorption problem.
References
- Schrier SL. Etiology and clinical manifestations of vitamin B12 and folic acid deficiency. http://www.uptodate.com/home/index.html. Accessed Jan. 19, 2009.
- Pernicious anemia. National Heart, Lung and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/prnanmia/prnanmia_all.html. Accessed Jan. 27, 2008.
- Folate. The Merck Manuals Online Medical Library: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec01/ch004/ch004c.html#sec01-ch004-ch004c-247. Accessed Jan. 28, 2009.
- Vitamin B-12. The Merck Manuals Online Medical Library: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec01/ch004/ch004i.html#sec01-ch004-ch004j-379. Accessed Jan. 28, 2009.
- Vitamin C. The Merck Manuals Online Medical Library: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec01/ch004/ch004j.html#sec01-ch004-ch004k-403. Accessed Jan. 28, 2009.
- Dietary supplement fact sheet: Vitamin B12. Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/vitaminb12.asp#h3. Accessed Jan. 28, 2009.
- Dietary supplement fact sheet: Folate. Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/folate.asp. Accessed Jan. 28, 2009.
- Food sources of selected nutrients. Dietary Guidelines for Americans 2005. USDA and Department of Health and Human Services. http://www.health.gov/dietaryguidelines/dga2005/document/html/AppendixB.htm. Accessed Jan. 28, 2009.
- Alcoholic beverages. Dietary Guidelines for Americans 2005. USDA and Department of Health and Human Services. http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter9.htm. Accessed Jan. 28, 2009.
