Syringes come in a variety of sizes, but the majority of clinically used syringes measure in millilitres per cubic centimetre. A clinical syringe that is the exception to this rule is the specialised, orange-tipped, insulin syringe. Overall, four categories of syringes exist, each with its own method of measurement that depends on its volume or capacity. Learning to correctly measure using a syringe is vital to administering the appropriate amount of fluid or medication.
Select the appropriate syringe for your purpose, whether injection of medication or administration of a tube feeding. Keep in mind, when administering a thick fluid or large amounts of fluid, select a larger volume syringe. Determine whether your purpose for using a syringe requires a needle or tube, and if so, which size is appropriate. For example, administering a tuberculin test requires using a watery tuberculin agent and uses a small half-inch, 25- to 27-gauge needle; however, collecting a blood sample, which is thick, requires using a larger 16- to 17-gauge needle.
Use a standard 3 millilitre per cubic centimetre syringe. This is the most common syringe used in the clinical setting for intramuscular and other types of injections. These syringes measure in tenths of a millilitre per cubic centimetre.
Use a 1 millilitre per cubic centimetre syringe. This is the syringe commonly used to inject insulin, to administer tuberculosis skin tests, and to administer powerful medications such as the blood thinner heparin. These syringes always measure in hundredths of a millilitre per cubic centimetre.
Use a syringe with a volume greater than 3 millilitres per cubic centimetre. These syringes come in four sizes (5, 6, 10, and 12 millilitres per cubic centimetre) and are commonly used, with a needle, for injecting large doses of medications or, without a needle, to give infants oral medications. Regardless of volume size and purpose, these syringes measure in two-tenths of a millilitre per cubic centimetre.
Use a syringe with a volume of 20 millilitres per cubic centimetre or greater. These syringes are commonly used for feeding individuals who rely on feeding tubes and measure in 1 millilitre per cubic centimetre. When syringes are used for feeding it is important to remove the plunger, pour the fluid into the syringe, and allow gravity to move the fluid through the feeding tube. Pushing feeding fluids with the plunger can cause serious stomach problems.
Read the syringe from the top of the rubber plunger inside the syringe. Align this plunger with the amount of fluid you wish to administer. For example, if you are using a 3 millilitre per cubic centimetre syringe and you need to inject 2.5 millilitres per cubic centimetre, pull the plunger back until the top of the plunger is aligned with the marking for 2.5 millilitres per cubic centimetre.