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Photo of Vetsulin syringe box


Vetsulin® (porcine insulin zinc suspension), from Merck Animal Health, is the first and only FDA-approved veterinary insulin for the treatment of diabetes mellitus in dogs. The concentration of Vetsulin is 40 IU per mL of solution. To avoid dosing errors when administering Vetsulin to dogs, a U-40 syringe must be used.

Merck Animal Health has available U-40 syringes in two sizes—a 1 mL syringe and a 0.5 mL syringe for smaller dogs. Syringes are available in boxes of 100.

Advise pet owners not to reuse insulin syringes. After a single use, insulin syringes and needles should be disposed of in approved sharps or biohazard containers.

U-40 versus U-100

Vetsulin is presented in a glass vial at a concentration of 40 IU per mL of solution. To avoid dosing errors when administering Vetsulin to dogs, it is important to use a U-40 syringe. USE OF A SYRINGE OTHER THAN A U-40 SYRINGE WILL RESULT IN INCORRECT DOSING.

Some dog owners may attempt to replenish their syringe inventories and/or insulin supply from their local human pharmacies. Pharmacies carry U-100 (100 IU/mL) 1 mL and 50 IU/mL 0.5 mL syringes only. They do not stock 40 IU/mL 1 mL syringes, nor do they stock Vetsulin.

Using a U-100 syringe with Vetsulin would result in a dog receiving two and a half times less insulin than required. Human insulins are formulated at a concentration of 100 IU/mL. If a client uses a U-40 syringe with a 100 IU insulin preparation, they would be injecting two times the amount of insulin necessary, which could result in fatal hypoglycemia.

Most pharmacists are not aware of Vetsulin nor the U-40 syringes recommended for use with this product. As noted above, substituting a 100 IU/mL insulin product and/or a 100 IU/mL 1 mL syringe without proper dosage conversion could result in unsuccessful regulation, hypoglycemia, and even death.

As this potential situation can be fatal, it is strongly advised to educate clients to purchase both Vetsulin and the U-40 syringes from your veterinary clinic.


Merck Animal Health has developed a video that guides pet owners step by step through the administration of Vetsulin. This video is intended as a supplement to directions you provide. Pet owners can access the video on the pet owner section of