Infusions come in different forms, depending on what you are treating or promoting. There are four main types of infusions: IV of intravenous therapy is the most common. It delivers fluid containing the medication or nutrients directly into the bloodstream. Most people will have this done when they go in for surgery. Epidural injections are delivered directly to the spine. This is most often done to deliver pain medication to the spinal column for severe back pain, women giving birth, or pain in the pelvic regions. Subcutaneous infusions are the second most common type. Their most common use is for insulin injections. The medication is delivered through the second layer of skin, known as the cutis. Intramuscular infusions are injections directly into the muscle. The medicine is quickly absorbed into the muscle and then slowly released into the body.