Is It Okay To Use A B12 Injection With Insulin Syringes? Types of injections explained! Understanding the angles: intramuscular (im) : injects deep into the muscle at 90. subcutaneous (sc) : goes under the skin at 45. intravenous (iv) : B12 Injection sites + How to use B12 Shots Safely VITAMIN B12 INJECTION Types of injections explained Intramuscular (IM) Inserted at 90 to deliver medication deep into the muscle, allowing relatively fast absorption due to rich blood supply. Subcutaneous (SC) Inserted at about 45 Different types of injection: Intramuscular (IM) Subcutaneous (SC) Intravenous (IV) Intradermal (ID) : r coolguides