What Happens If You Inject B12 Wrong: 6 Red Flags Not all shots are the same here's a guide Injections are a fast, effective way to deliver medications, nutrients, and vaccines directly into the body but not all injections are the same. VITAMIN B12 INJECTION 1000 mcg mL Is It Okay To Use A B12 Injection With Insulin Syringes? 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