What does the term "under the skin" refer to in medical administration?

The term "under the skin" in medical administration specifically refers to subcutaneous (SQ) injections. These are administered into the tissue layer between the skin and the muscle, allowing for the slow absorption of the medication into the bloodstream. This method is often used for vaccines, insulin, and other medications that require steady absorption over time.

The other routes of administration have different meanings: intramuscular (IM) refers to injections that are given into the muscles; intradermal (ID) means injections that are administered between the layers of the skin; and intravenous (IV) indicates that the medication is delivered directly into the bloodstream via a vein. Each route has its own applications and absorption rates, highlighting why "under the skin" is uniquely associated with subcutaneous injections.