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.