Important for metabolism, energy, stress. Opens possibility of ancillary supplement support with oral/sublingual/injectable B12 and other compounded supplements. When to order: Anemia (low hemoglobin or hematocrit) in the presence of an elevated MCV (>98). An elevated MCV >98 is a good indication to order B12 level even without clinical anemia evident. Low suspected dietary intake (vegan, vegetarian, low red meat intake, no B12 supplementation). Gastric bypass patients, any patients with surgical procedures performed on intestines (especially distal ileum). Patients seeking enhanced metabolism, energy, weight loss, or any patients interested in possible B12 supplementation