An intravenous drug (IV drug) is a drug administered intravenously, either by an intravenous drip or a syringe. As it is one of the most effective methods of administering drugs with rapid effect, it is used widely used in medical practice and by recreational drug users.

The reuse of syringes to administer drugs intravenously is a primary vector for diseases that can be transmitted through blood and the practice is generally forbidden in medicine, although in some areas syringe or needle reuse is necessary for economic reasons (such as in sub-Saharan Africa). Inadequate sterilization of needles or syringes between uses has caused or contributed to several serious outbreaks of disease in Africa, such as Ebola.

Reuse, known colloquially as needle sharing, is common among users of illegal drugs. This has caused an increase in the spread of diseases such as hepatitis and AIDS; because of this illicit IV drug use has become a public health threat and programs to decrease needle sharing have been established, often in contravention of the law (see harm reduction).