The secret is small, frequent doses, daily at least if you have neurological B12 deficiency symptoms. When you dissolve our 40,000μg of B12 in 10ml of saline, 0.3ml syringes will give you 33 shots, each having 1,200μg of B12. Alternatively, you'll get 20 shots of 2,000μg each if you use 0.5ml needles. We prefer the former, as 2,000μg is still a lot for a single shot, and it probably won't be fully absorbed. You'll get more B12 absorbed per dollar spent if you inject with 0.3ml needles. 1,200μg per shot is still a lot - that's as much B12 as you'll find in 250 steaks!