People tend to buy syringes without a prescription at their local pharmacies but each state has certain laws and guidelines when buying these syringes. Lets use Illinois for an example:
A hypodermic needle is a hollow needle commonly used for a syringe to inject substances into the body or extract liquids from it such as people injecting insulin. They may also be used to take liquid samples ex) taking blood from a vein.

In Illinois  The Hypodermic Syringes and Needles Act was passed on 1955 stating people 18 + years of age where only allowed to buy 20 syringes/needles. Lets face it many drug users go to their local pharmacy to buy needles to inject illegal drugs for satisfaction, so this is why there is a certain amount of syringes to buy. Some pharmacists may ask why you need that many syringes and some do not ask. In Illinois you do not need a prescription to buy these needles.  To check your state guidelines visit-