ProZinc (PZI Insulin) for Cats: Uses, Dosing & Cost

This information is for educational purposes only. Never give your pet any medication without your veterinarian's guidance. Dosing, frequency, and safety depend on your pet's specific health profile.

ProZinc is a prescription veterinary insulin used to help manage diabetes mellitus in cats. Its full generic name is protamine zinc recombinant human insulin, and it is a U-40 insulin, meaning it contains 40 units of insulin per mL. That concentration matters because cats taking ProZinc need U-40 syringes for accurate dosing.

In cats, ProZinc is considered a long-acting insulin. It is designed to lower blood glucose more gradually than shorter-acting products, which can make it a practical option for twice-daily home treatment. Merck Veterinary Manual lists protamine zinc insulin among the most commonly used starting insulins for newly diagnosed diabetic cats, alongside glargine.

ProZinc is a suspension, not a clear solution, so the vial is usually mixed by gently rolling before each dose rather than shaking. It is given under the skin and is typically paired with a consistent feeding routine, home observation, and regular recheck testing with your vet.

For many pet parents, the biggest adjustment is not the injection itself but the routine. With coaching from your vet, most families learn to give insulin safely at home and track appetite, thirst, urination, body weight, and energy level.

ProZinc is used to treat feline diabetes mellitus, a condition where the body cannot regulate blood sugar normally. Cats with diabetes often drink more, urinate more, lose weight despite eating, and may seem weak or less active. Insulin therapy helps move glucose from the bloodstream into the body's cells so it can be used for energy.

In practice, your vet may choose ProZinc for a cat that needs ongoing insulin support and would benefit from a long-acting product dosed every 12 hours. It is commonly used in newly diagnosed cats and in cats already known to have diabetes that need continued insulin regulation.

Treatment goals are broader than lowering a number on a glucose test. Your vet is usually trying to improve day-to-day clinical signs, reduce the risk of complications like hypoglycemia or diabetic ketoacidosis, and in some cats, support the possibility of diabetic remission. Cornell notes that careful monitoring, early treatment, and diet changes can improve outcomes.

Some cats may be candidates for other treatment approaches, including different insulin types or, in selected cases, newer oral diabetic medications. ProZinc is one option among several, and the best fit depends on your cat's health status, eating habits, home routine, and monitoring plan.

ProZinc dosing must be individualized by your vet. A commonly cited starting dose for newly diagnosed cats is about 0.25 U/kg, which often works out to 1 unit per cat every 12 hours, given under the skin. Merck advises using the cat's estimated ideal body weight, not actual weight, when calculating a starting dose, and starting conservatively. Initial doses generally should not exceed 2 units per cat.

ProZinc is usually given with or right after a meal. If your cat is not eating or is vomiting, the FDA client information sheet advises not giving the prescribed dose until you have spoken with your vet. Because ProZinc is a U-40 insulin, using the wrong syringe can cause a major dosing error. Pet parents should use U-40 syringes only unless their vet has given very specific alternative instructions.

Dose changes are based on the whole picture, not one reading alone. Your vet may use a blood glucose curve, fructosamine testing, body weight, water intake, appetite, urine output, and home glucose data if available. Merck notes that cats are often rechecked 5 to 7 days after starting treatment, and dose increases should not be made too often. Cornell also emphasizes close monitoring early in treatment to avoid both underdosing and dangerous low blood sugar.

Never increase, decrease, skip, or double a dose on your own unless your vet has already given you a written plan for that situation. If you miss a dose, many vets recommend calling for guidance rather than trying to "catch up." Double dosing can cause a life-threatening hypoglycemic episode.

See your vet immediately if your cat has signs of low blood sugar. This is the most important risk with ProZinc and other insulins. According to the FDA client sheet, signs can include weakness, lethargy, staggering, muscle twitching, behavior changes, seizures, coma, and death.

Cornell also lists vomiting, poor coordination, and severe weakness among possible signs of hypoglycemia. If your cat is conscious, the FDA advises rubbing corn syrup or honey on the gums and contacting your vet right away. If your cat is unconscious or having a seizure, that is an emergency and your cat needs immediate veterinary care.

Not every problem on insulin is caused by overdose. Cats that are still poorly regulated may continue to have increased thirst, increased urination, weight loss, or appetite changes. On the other hand, a cat whose insulin needs have changed because of weight loss, infection, pancreatitis, steroid use, or another illness may suddenly become over- or under-controlled.

Call your vet promptly if you notice reduced appetite, vomiting, unusual sleepiness, wobbliness, tremors, or any sudden change in behavior. These signs do not confirm a cause, but they do mean your cat's diabetes plan may need to be reassessed.

ProZinc can interact with medications or diseases that change your cat's insulin needs. The FDA client information sheet specifically warns that low blood sugar can happen when there are changes in the body's insulin requirement or when drug effects alter diabetic control. That is why your vet should know about every medication and supplement your cat receives, including over-the-counter products.

In real-world practice, drugs that may affect diabetic regulation include corticosteroids such as prednisolone, some progestins, and other medications that can raise blood glucose or increase insulin resistance. Illnesses like infection, pancreatitis, hyperthyroidism, or kidney disease can also change how much insulin a cat needs, even if the insulin itself has not changed.

The most important safety point for pet parents is this: do not assume a new medication is automatically compatible with your cat's diabetes plan. If another vet prescribes a drug, or if you are considering a supplement, ask whether it could affect appetite, blood sugar, or insulin sensitivity.

There is also a practical interaction issue with supplies: using the wrong syringe acts like a dosing interaction because it changes how much insulin is actually delivered. ProZinc should be paired with U-40 syringes, stored as directed, and discarded if the vial develops clumps or visible white particles after gentle rolling.