Diagnosis

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:

• 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.