How quickly does B12 shot work for energy and cognitive focus?
Dr. Susan Carter, MD: Endocrinologist & Longevity Expert
Dec 01, 2025 · 13 min read
Vitamin B12 shots can quickly correct low B12 in people who cannot absorb pills, but the benefits, timing, and safe injection technique depend on your health, your dose, and exactly where and how the shot is given. “For the right patient, a B12 injection is like fixing a blocked fuel line. If you’ve been running ...