when are b12 injections given B12 Injection Dosage and Frequency:

If you have a healthy digestive system, youll very efficiently absorb the first two micrograms of an oral dose (about 70 to 90 percent of it), says Green

Anemia Prevention: B12 is crucial for red blood cell formation, preventing the fatigue and weakness associated with B12-related anemia

Standard research protocols generally use 500600 mcg daily, administered as a single morning dose or split into 250300 mcg twice daily

Nature Reviews Endocrinology, 16(3), 135-146

Your provider determines this based on your health status and response

Because alcohol interferes with how the body absorbs, stores, and metabolizes these nutrients, replenishing them through a nutrient-rich diet or a B-complex supplement (with a clinician's input) is one of the steps the post recommends for people cutting back or quitting