A syringe is a plastic or glass cylinder that contains a plunger that goes in one end and typically has a needle attached to the other. The term "syringe" can refer either to all three components — the cylinder, plunder, and needle — or just to the cylinder portion. Syringe sizes are indicated in milliliters and can range from 0.25 ml up to 450 ml. They also can be stated in cubic centimeters, where 1 cc is the approximate equivalent of 1 mL. These numbers indicate the volume of liquid that the cylinder is able to hold.
When referring to the unit as a whole, syringe sizes also might be given for the needle portion of the syringe because the size of the cylinder is often used to determine the size of the needle that will be attached to it. The needles themselves are categorized by length as well as the needle's gauge, indicating the overall thickness of the needle. Contrary to most measurement systems, the higher the needle's gauge, the smaller it actually is.
Insulin syringes, for example, are found in three common sizes: 1 cc, 1/2 cc, and 3/10 cc. The correct size syringe to use is determined by the average size of the dose of insulin that the patient administers. An insulin syringe also can be categorized by how many units of insulin it is designed to hold. Each mL or cc contains 100 units of insulin. A 3/10 cc syringe will hold up to 30 units of insulin, and a 1 cc syringe will hold up to 100 units of insulin.
There are other types of syringes, however, that do not include a needle as a component of their design. These include oral syringes, which most often are used to dispense liquids to babies or small children. Oral syringes differ from standard syringes only because of their tapered tip in place of a needle, so the same sizes are used to indicate how much liquid can be contained within the cylinder.
The final category of syringe contains neither a needle, a plunger or even a cylinder, and they are designed to clear wax and mucous from ear and nasal passages. Their lack of a cylinder means that both ear and nasal syringes are not categorized by standard syringe sizes at all. Unlike injection and oral syringes, this type are created in a bulbous design, comprised of a thin, rubber-like material and tapered to a rounded tip on one end. Ear and nasal syringes are typically found in one standard size, usually about 2 to 3 ounces (57 to 85 ml) in volume.