Vitamin B12 Injections Energy Boost The Center Medical Here's a scenario that happens more than we'd like to admit: a patient on metformin for years comes in reporting tingling in their feet. You work them up for diabetic peripheral neuropathy, Benefits of B12 Shots for Energy and Focus For anyone that has had to do vitamin b12 injections.. do they give you nausea, diarrhea, and a bad headache? I did my first injection this afternoon and a few hours later