Blood test for serum vitamin B12
Complete blood count
Mean corpuscular volume test
Methylmalonic acid test
Homocysteine test
Holotranscobalamin test
Intrinsic factor antibody test
Parietal cell antibody test
Folate level test
Peripheral blood smear
Neurological examination
Review of diet and medical history
Assessment for symptoms such as fatigue, numbness, tingling, or memory problems