When choosing insulin syringes, take into account the amount of insulin you need to inject at one time. There is no point in buying a large syringe if your dose is small, as a smaller insulin syringe will be more accurate and easier to measure. At the same time, the syringe should be big enough to fit your entire dose. Also, if you need to mix two types of insulin in the syringe, you should opt for a larger size. Insulin syringes come in three sizes: 0.3 ml (30 units), 0.5 ml (50 units), and 1 ml (100 units). You should also make sure the markings on the syringe are clear. If you have poor eyesight, insulin pens might be a better choice. Insulin syringes aren't the only thing to consider, as the needle length and gauge are also important for your comfort and precise injections. If unsure, ask your healthcare professional and they will guide you in terms of needle length and the appropriate injection technique for you.