The Full form of IM is Intramuscular Injection. IM is a technique used to deliver a medication deep into the muscles. This allows the medication to be absorbed into the bloodstream quickly. Muscles in humans have larger and more numerous blood vessels than subcutaneous tissue and injections here usually have faster rates of absorption than intradermal injections or subcutaneous injections. Depending on the injection site, an administration is limited to 2 to 5 milliliters of fluid. You may have received an IM at a doctor’s office the last time you got a vaccine, like the flu shot. In some cases, a person may also self-administer an intramuscular injection. For example, certain drugs that treat rheumatoid arthritis or multiple sclerosis may require self-injection. In modern medicine, Intramuscular injections are a common practice. They’re used to deliver drugs and vaccines. Almost all injectable vaccines and several drugs are delivered this way.IM injections are used when other types of delivery methods aren’t recommended. These include oral (swallowed into the stomach), intravenous (injected into the vein) and subcutaneous (injected into the fatty tissue just under the layer of skin). IM injections may be used instead of intravenous injections because some drugs are irritating to veins, or because a suitable vein can’t be located.