The Difference Between U40 & U100 Insulin Syringes

U40 and U100 insulin syringes are used to dose insulin for cats and dogs and is based on the insulin prescribed. If the right-size syringe cannot be found, it is possible to adjust the insulin dose for the other syringe type.

  1. U40 Insulin and Syringe

    • Protamine zinc insulin (PZI) commonly comes in a U40 dose, which means there are 40 units of active insulin in each milliliter of liquid. U40 syringes should be used with U40 insulin.

    U100 Insulin and Syringe

    • U100 insulin means there is 100 units of PZI per milliliter of liquid and it should be dosed with the U100 insulin syringe.

    Differences Between U40 and U100

    • The U100 insulin syringe holds 2.5 times more liquid than the U40 insulin syringe.

    Which Syringe to Use

    • Use the syringe size recommended by your veterinarian.

    Convert Dosage

    • If you are unable to find the proper-size syringe, you can convert the dosage; however, you should contact your veterinarian for correct dosage. For a chart on converting the dosage, visit caninediabetes.org.