Doctors diagnose vitamin deficiency anemias through blood tests that check:
- The number and appearance of red blood cells. People with anemia have fewer red blood cells than normal. In vitamin deficiency anemias related to a lack of vitamin B-12 and folate, the red blood cells appear large and underdeveloped. In advanced deficiencies, the numbers of white blood cells and platelets also might be decreased and 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 can cause similar signs and symptoms.
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, such as:
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- 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 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.
- Lichtman MA, et al. Williams Hematology. 8th ed. New York, N.Y.: The McGraw-Hill Companies; 2010. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=69. Accessed Sept. 14, 2013.
- Papadakis MA, et al. Current Medical Diagnosis & Treatment 2013. 52nd ed. New York, N.Y.: The McGraw-Hill Companies; 2013. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=1. Accessed Sept. 14, 2013.
- Schrier SL. Etiology and clinical manifestations of vitamin B12 and folate deficiency. http://www.uptodate.com/home. Accessed Sept. 14, 2013.
- Stabler SP. Vitamin B12 deficiency. New England Journal of Medicine. 2013;368:149.
- Schrier SL. Diagnosis and treatment of vitamin B12 and folate deficiency. http://www.uptodate.com/home. Accessed Sept. 14, 2013.
- Dietary reference intakes (DRIs): Recommended intakes for individuals, vitamins. Institute of Medicine. http://iom.edu/Global/Search.aspx?q=dietary+reference+intakes+vitamin&output=xml_no_dtd&client=iom_frontend&site=iom&proxyreload=1&ie=UTF-8&ulang=&ip=126.96.36.199&access=p&sort=date:D:L:d1&entqr=3&entqrm=0&start=10. Accessed Sept. 14, 2013.
- Dietary Guidelines for Americans, 2010. U.S. Department of Health and Human Services. http://www.cnpp.usda.gov/DGAs2010-PolicyDocument.htm. Accessed Sept. 14, 2013.