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Syringe & Needle Basics
by Erowid
Mar 2003
[Adapted from Harm Reduction Coalition's pamphlet
Getting Off Right: A Safety Manual for Injection Drug Users]
Syringes and needles are designed for the purpose of introducing a drug into the body. The term "syringe" technically refers to the reservoir (that holds the liquid) and the plunger (which pushes the liquid out of the reservoir). The "needle" is the part that enters the body, whether into a vein, under the skin, or into muscle. The word "syringe" is also sometimes used to refer to the entire reservoir/plunger/needle combination.

The two most commonly available varieties of syringe/needle sets are insulin and tuberculin. "Insulin needles" are used by diabetics for injecting insulin, while "tuberculin needles" are used to inject tuberculin during the diagnosis of the tuberculous infection.

Many countries and U.S. states have legal restrictions on possession and over-the-counter sale of needles. Drug paraphernalia laws often prohibit possession of syringes for purpose of illicit drug use. Medical prescription laws often prohibits over-the-counter pharmacy sales, or possession without a prescription. As of 2002, six U.S. states require a prescription for the purpose of a sterile syringe: California, Illinois, Pennsylvania, New Jersey, Delaware and Massachussetts. [from]

Syringes sold by pharmacies and online medical suppliers are typically for diabetics and other uses including post-operative conditions, vitamin deficiencies and intramuscular medications. They come in a variety of sizes, but the most common reservoir size is 1cc (1 cubic centimeter (cc) = 1 milliliter), with a 25 gauge needle size or smaller.

NEEDLE GAUGE refers to the size of the bore or hole in the needle. The higher the gauge, the thinner the needle (and the smaller the hole). A 28 gauge needle (abbreviated 28G) is therefore thinner than a 25 gauge needle, which is in turn thinner than an 18 gauge needle. Different gauge needles are used for different administration methods (see below).

NEEDLE LENGTH. Insulin needles are typically 1/2 inch in length and tuberculin needles are typically 5/8 of an inch in length. As inscribed on packaging, needle length appears after the gauge number: "28G 1/2" refers to a 28 gauge needle that is 1/2 inch long.

SYRINGE RESERVOIR SIZE. Standard insulin syringes typically have a 1cc reservoir and are calibrated by .10cc's along the barrel of the reservoir. Most drug injectors find this size ideal and would rarely need use of a larger syringe, although some like to use a smaller 1/2 cc syringes. Syringes other than 1cc in size may be more difficult to obtain.

PLUNGERS. The plunger is used to push the liquid drug out of the reservoir, through the needle and into the body (either into a vein, under the skin, or into a muscle). The plungers on some brands of syringes are easier to manipulate than on others.

INTRAMUSCULAR. Larger gauge (frequently 23G or 21G), longer needles are often used for intramuscular injections. Muscle syringes are usually 1cc–-but sometimes 2 to 5 ccs–-with up to a 1-1/2 inch long point.

INTRAVENOUS. Intravenous injectors typically use shorter needles no larger than 25G. Most intravenous injectors use either a standard insulin set (orange cap) or a tuberculin needle and syringe (frequently called a bluetip because of its color).

ONE-PIECE SETS VERSUS TWO-PIECE, DETACHABLE SETS. With some types of injection equipment, the needle detaches from the syringe resulting in two separate pieces. Standard insulin injection equipment is typically one piece, and has a 27G or 28G needle (and an orange cap). Tuberculin needles and syringes are often detachable and typically have a 25G needle. NOTE: Certain brands of tuberculin syringes have an orange cap, making them easy to confuse with insulin syringes.

Needles & Syringes section of HRC pamphlet, "Getting Off Right"
Harm Reduction Coalition links: Safer Injection/Injection Hygiene
Investigation into the Effectiveness of Filters...
Giving Medicine by Intramuscular Injection

Needle Exchange Vault
States Syringe Statutes and Regulations (
Possession and Disposal (Temple University)
The Legality of Prescribing and Dispensing Sterile Injection Equipment (table)

Intramuscular (IM)
Intravenous (IV)
Subcutaneous (SC)

Used Needles