For subcutaneous injections, using shorter needles (4 5mm) is the safest choice to ensure medication stays in the fatty layer and avoids muscle injury. A 4mm needle is ideal, minimizing pain while keeping B12 Shots and Mounjaro: Safety, Benefits and Considerations Bolt Pharmacy How To Self Administer Vitamin B12 Injections Invigor Medical How to self inject intramuscular vitamin B12 Overview Guy's and St Thomas' NHS Foundation Trust Subcutaneous injections 45 90 angles USE 90 for MOST patients USE 45 for small guage needles, low body fat (body builders malnourished) Orange tops = insulin syringe measured in UNITS B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics