Injection (medicine)
An injection is an infusion method
Route of administration
A route of administration in pharmacology and toxicology is the path by which a drug, fluid, poison, or other substance is taken into the body.-Classification:Routes of administration are usually classified by application location...

 of putting fluid into the body
With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...

, usually with a hollow needle
Hypodermic needle
A hypodermic needle is a hollow needle commonly used with a syringe to inject substances into the body or extract fluids from it...

 and a syringe
A syringe is a simple pump consisting of a plunger that fits tightly in a tube. The plunger can be pulled and pushed along inside a cylindrical tube , allowing the syringe to take in and expel a liquid or gas through an orifice at the open end of the tube...

 which is pierced through the skin to a sufficient depth for the material to be forced into the body. An injection follows a parenteral route of administration; that is, administered other than through the digestive tract.

There are several methods of injection or infusion, including intradermal, subcutaneous
Subcutaneous injection
A subcutaneous injection is administered as a bolus into the subcutis, the layer of skin directly below the dermis and epidermis, collectively referred to as the...

, intramuscular
Intramuscular injection
Intramuscular 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 . It is used for particular forms of medication that are administered in small amounts...

, intravenous, intraosseous, and intraperitoneal.