injecting b12 into a vein Injections IV Infusions What happens if you inject
Description
If you see any blood being draw, you're in a vein

2011, National Institutes of Health
Niacin is involved in the DNA metabolism and repair, cellular signaling events, cell migration [24], and decreases the expression of the pro-inflammatory cytokines, IL-1, IL-6, and TNF- by the macrophages [25]

The general recommendation is to receive an injection every 4-6 weeks