Intramuscular (also IM or im) injection is the injection of a substance directly into a muscle. In medicine, it is one of several alternative methods for the administration of medications (see route of administration). It is used for particular forms of medication that are administered in small volumes. Depending on the chemical properties of the drug, the medication may either be absorbed fairly quickly or more gradually. Muscles have larger and more blood vessels than subcutaneous tissue and injections here usually have faster rates of absorption than subcutaneous injections or intradermal injections. Depending on the injection site, an administration is limited to between 2 and 5 milliliters of fluid.