To help detect early and/or mild vitamin B12 deficiency; to help diagnose methylmalonic acidemia, a rare inherited metabolic disorder

When you have a low vitamin B12 level and/or have symptoms of B12 deficiency such as numbness, tingling in the hands or feet, trouble walking, swelling of body tissues, or yellowing of the skin or eyes; as part of newborn screening

You may be instructed to fast before sample collection for this test.