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 Intramuscular injection is shown at 90 because the goal is to reach the muscle, the deepest layer in this comparison. That route is chosen when medication needs reliable absorption through the muscle's Cyanocobalamin Vitamin B12 Injection 1000 mcg Mountainside Medical Cyanocobalamin 1,000 mcg mL Injection 1 mL McKesson