are vitamin b12 injections intramuscular How to self-inject - Overview Best Vitamin B12 Injection Sites
Description
1948 Sep;33(9):1123-32

Injection to a nerve may cause some amount of pain initially but at tolerable levels
Heavier individuals with more adipose tissue often benefit from doses at the higher end of the standard range (450-500mcg)
B12 Injections B12 injections are widely used by people on weight-loss journeys because they help fight fatigue, a common issue during calorie restriction or GLP-1 medication use

This product must not be used for intravenous injection