Hypodermic needle, one of a class of medical instruments, is a very thin, hollow tube with a sharp tip containing a small opening. It is usually used with syringes, manual devices with plungers, to inject substances into the body (such as saline, a solution containing various drugs or liquid drugs), or to extract fluids from the body (such as blood). They are used to extract fluid samples from the body, such as blood from venipuncture veins. Large caliber subcutaneous intervention is especially useful in the treatment of massive bleeding or shock. The following article shall tell you more about hypodermic needles.