One of the main uses of disposable hypodermic syringe is to inject drugs, vaccines and other substances. The appropriate dose of the drug or vaccine is drawn into the syringe, and the fluid is drawn out of the open end by pushing the plunger, or through the disposable hypodermic syringeneedle. Injections can be injected directly into the body, such as intramuscularly or intravenously, and then delivered into the bloodstream; the drug depends on the drug.

Blood samples can also be collected using a disposable hypodermic syringe. Attach the syringe to the hypodermic needle inserted into the vein and pull the plunger back to create suction. Blood is drawn by suction, into the cylinder of a syringe, and sometimes into an attached test tube for necessary blood diagnostics and tests.