Vetsulin (porcine insulin zinc suspension) is the first and only FDA-approved insulin available in the U.S. for treating diabetic dogs and cats. Vetsulin controls levels of glucose in the blood to help alleviate diabetic symptoms. Vetsulin Insulin is available as a 10 ml vial that is used with U-40 insulin syringes (sold separately). Vetsulin requires a prescription from your veterinarian. Vetsulin Insulin requires refrigeration and must be kept at refrigerator temperatures at all times. To ensure proper temperature, it requires overnight shipping at an additional cost.