when are b12 injections given Do Help with Fatigue and Low Energy? Vitamin B12 Injections for Energy,

Amazon told GeekWire that starting Dec

People may not be able to take vitamin B12 shots if they have a history of sensitivity to vitamin B12

Oral administration of high-dose vitamin B 12 (1 to 2 mg daily) is considered as effective as intramuscular administration for correcting anemia and neurologic symptoms Despite many studies suggesting oral administration of vitamin B 12 to be easy, effective and less costly than intramuscular administration, debate surrounds the effectiveness of the oral route

Information for Patients: Patients with pernicious anemia should be informed that they will require monthly injections of vitamin B12 for the remainder of their lives

I think the half life is much faster than that