# How Long Does ProZinc Last in Cats? Duration and Syringes ProZinc insulin for cats how long does it last? In most cats, a single ProZinc (protamine zinc insulin) injection keeps working for roughly 10 to 14 hours, which is why veterinarians prescribe it twice daily. Its effect is biphasic, meaning it often drops blood sugar once early and again later in the dosing interval [1]. Because the duration falls short of a full 24 hours, timing your cat's shots about 12 hours apart matters. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - ProZinc is a long-acting protamine zinc insulin (PZI) given by subcutaneous injection, usually twice a day [2]. - Its duration of action is similar to insulin glargine and longer than lente insulin in healthy cats [1]. - In one study, PZI produced two blood glucose nadirs (low points), one around 4 hours and a second around 14 hours after injection [1]. - Because the effect does not reliably last a full day, most cats need two shots spaced roughly 12 hours apart [2]. - ProZinc must be given with U-40 syringes, not the U-100 syringes used for many human insulins. ## What Is ProZinc and What Is It Used For? ProZinc is a brand of protamine zinc insulin made for cats and dogs. It is a long-acting insulin that veterinarians prescribe to manage feline diabetes mellitus. The goal is to control blood glucose, reduce diabetic symptoms like excessive drinking and urination, and give the cat's pancreas a chance to recover some function. Remission is a realistic goal for some cats. In a study of 185 cats treated with a loose-control approach using protamine zinc insulin, the remission probability was 56.2% [3]. Remission means the cat no longer needs insulin. Factors linked to a higher chance of remission included lower mean blood glucose during treatment, lower mean insulin dose, and no recent corticosteroid use before diagnosis [3]. Your veterinarian will decide whether ProZinc is the right insulin for your cat. Other long-acting options exist, including insulin glargine. You can read more about that option in [Insulin Glargine for Cats: Feline Diabetes Dose and Glucose Curve](/knowledge/veterinary-medicine/calculators-clinical-tools/insulin-glargine-for-cats-feline-diabetes-dose-and-glucose-curve). ## How ProZinc Works in Your Cat's Body Insulin moves glucose from the bloodstream into cells. Without enough insulin, glucose builds up in the blood while the body's tissues starve for energy. ProZinc replaces the insulin your cat's pancreas can no longer make in sufficient amounts. ProZinc is formulated with protamine and zinc, which slow its absorption after injection. That slower absorption is what stretches its action over many hours instead of minutes. The timing of its effect is not a single smooth curve. In healthy cats given protamine zinc insulin, researchers found a biphasic pattern with nadirs at about 4 hours and about 14 hours after the injection [1]. The second nadir occurred at a similar time to insulin glargine's single nadir [1]. The overall duration of action was similar for glargine and PZI, and both lasted longer than lente insulin [1]. This pattern explains a lot about how your veterinarian monitors your cat. A blood glucose curve done in the clinic may show two low points, and the second one can matter as much as the first. ## Dosing Basics: Who Decides and How It Is Given ### Who sets the dose Your veterinarian sets the dose. It is calculated from your cat's body weight, current blood glucose and fructosamine levels, clinical response, and other health conditions. Never adjust the dose on your own based on a single glucose reading at home. In a clinical trial of 67 diabetic cats, doses of PZI were adjusted as needed over 45 days to reach glycemic control, and the mean dose increased significantly over that period [4]. That tells you something useful: the right dose often changes with time, and your veterinarian will expect to fine-tune it. ### How to give the injection ProZinc is given subcutaneously, meaning just under the skin. Common injection sites include the scruff, the side of the chest, or the flank. Rotate sites so the skin does not thicken. Give the injection at roughly the same times each day, about 12 hours apart, because the insulin does not last a full 24 hours [2]. ### Which syringes to use This is one of the most common and most dangerous mistakes owners make. ProZinc is a U-40 insulin, so it must be drawn up with U-40 syringes. U-100 syringes are made for a more concentrated insulin, and using them with ProZinc will deliver the wrong amount. Ask your veterinarian to confirm the syringe type and to show you exactly where to read the dose on the barrel. If your pharmacy gives you a different syringe brand than usual, check with your veterinarian before using it. ### What to do about a missed dose If you miss a dose, do not double up at the next scheduled time. Giving two doses close together can cause dangerous low blood sugar. Call your veterinarian for instructions, and keep a written log of every dose you give so you can report accurately. ## Side Effects of ProZinc in Cats | Side effect | How common or serious | What to do | |---|---|---| | Low blood sugar (hypoglycemia): weakness, wobbling, drooling, seizures | Uncommon but serious, and the most dangerous risk of any insulin | If you see these signs, rub a small amount of honey or corn syrup on the gums and call your veterinarian or an emergency clinic right away | | Poor appetite or vomiting | Can happen with diabetes itself or with insulin changes | Call your veterinarian if your cat skips more than one meal. See [Cat Not Eating: How Long Is Too Long?](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-eating-how-long-too-long) | | Increased drinking and urination that does not improve | Suggests the dose or insulin type may need review | Report it at your next visit or sooner if it worsens | | Injection site reactions, such as pain or swelling | Uncommon | Tell your veterinarian and rotate injection sites | | Weakness or lethargy | Can signal either high or low blood sugar | Check blood glucose if you monitor at home, and call your veterinarian | Low blood sugar is the emergency to watch for. Signs include stumbling, head tilting, glassy eyes, and collapse. Keep a sugar source on hand and know your emergency clinic's address before you ever need it. ## Who Should Not Take ProZinc and What Interacts With It ProZinc is not appropriate for every cat. Your veterinarian will weigh the risks if your cat has had a prior severe hypoglycemic episode, has significant liver or kidney disease, has an active infection, or is not eating reliably. Cats that are vomiting or not holding down food may need to skip a dose or change treatment, and only your veterinarian should make that call. Several medications and conditions can interfere with insulin's effect: - **Corticosteroids** can raise blood glucose and work against insulin. Recent pre-diabetic corticosteroid use was linked to a lower chance of remission in one study of 185 cats [3]. - **Other diabetes medications** taken at the same time can stack their effects and cause hypoglycemia. - **Progestins and some hormone treatments** can worsen insulin resistance. - **Infections, dental disease, and hyperthyroidism** are common reasons a cat's insulin stops working well. These need treatment, not just a higher insulin dose. Always tell your veterinarian about every medication, supplement, and topical product your cat receives, including anything you buy without a prescription. ## Overdose and When to Call for Help An insulin overdose can cause life-threatening hypoglycemia. Signs include severe weakness, disorientation, tremors, and seizures. If you think your cat received too much ProZinc, do not wait for symptoms. Call your veterinarian or a pet poison control hotline immediately, and have the insulin bottle and syringe on hand so you can report exactly how much was given. If your cat is already showing neurological signs like seizures or unresponsiveness, that is an emergency. Go to the nearest emergency veterinary clinic now. If you can do it safely, rub honey or corn syrup on the gums on the way. If your cat is alert and acting normally but you know the dose was wrong, still call. Your veterinarian may advise monitoring blood glucose at home, feeding a meal, or bringing the cat in. ## Limitations and When to Contact a Veterinarian No article can tell you what your individual cat needs. Dosing, monitoring schedules, and insulin choices depend on your cat's exam findings, lab work, and response to treatment. Your veterinarian is the only person who should adjust your cat's ProZinc plan. Contact your veterinarian the same day if: - Your cat vomits or refuses food after an insulin dose - You gave the wrong dose or used the wrong syringe - Your cat seems weak, wobbly, or unusually quiet after a shot - Your cat's water intake or urination suddenly increases Go to an emergency clinic now if: - Your cat has a seizure, collapses, or cannot stand - Your cat is unresponsive or breathing abnormally - You cannot rouse your cat or get it to swallow Schedule a routine visit if: - Home glucose readings are consistently high or low - Your cat's weight is dropping despite eating - You are running low on insulin or syringes and need a refill - You notice any change in appetite, thirst, or energy that lasts more than a day or two If your cat stops urinating or you are unsure whether litter box changes are normal, [How Long Can A Healthy Cat Go Without Peeing](/knowledge/veterinary-medicine/symptom-guides/how-long-can-a-healthy-cat-go-without-peeing) can help you judge urgency. ## Frequently Asked Questions ### Does ProZinc last 12 hours in every cat? No, the exact duration varies from cat to cat. The typical range is about 10 to 14 hours, which is why twice-daily dosing is standard [2]. Some cats clear insulin faster or slower based on weight, diet, activity, and other health conditions. ### Can I give ProZinc once a day instead of twice? Only if your veterinarian specifically tells you to. Because PZI does not reliably cover a full 24 hours, most cats need two injections about 12 hours apart [2]. A once-daily schedule can leave your cat with high blood sugar for part of each day. ### What happens if I give the shot at a different time each day? Occasional small shifts are usually tolerated, but large or frequent changes make blood sugar harder to control. Try to keep shots within about an hour of the same times daily. If your schedule changes, ask your veterinarian how to shift the timing safely. ### Can I use U-100 syringes with ProZinc? No. ProZinc is a U-40 insulin and requires U-40 syringes. Using U-100 syringes will draw up a different amount than intended and can cause a serious overdose or underdose. Always confirm the syringe type with your veterinarian and check the label each time you open a new box. ### Do I need to monitor blood glucose at home? Home monitoring helps many owners and veterinarians catch problems early, but it is not required for every cat. Your veterinarian may recommend a glucose curve in the clinic, a continuous glucose monitor, or home testing with a pet-specific meter. Ask which approach fits your cat and your comfort level. ### Can ProZinc put my cat into remission? Remission is possible for some cats. In one large study, the remission probability was 56.2% among cats treated with protamine zinc insulin using a loose-control approach [3]. Lower mean blood glucose during treatment and lower insulin doses were linked to a higher chance of remission [3]. Your veterinarian can tell you whether your cat is a realistic candidate. ### How long does ProZinc last in the bottle after opening? Follow the storage and discard instructions that come with your specific bottle, and ask your veterinarian or pharmacist if you are unsure. Insulin that has been stored improperly or kept past its recommended use window may lose potency, which can look like your cat's diabetes suddenly getting worse. ## Related Articles - [Insulin Glargine for Cats: Feline Diabetes Dose and Glucose Curve](/knowledge/veterinary-medicine/calculators-clinical-tools/insulin-glargine-for-cats-feline-diabetes-dose-and-glucose-curve) - [Cat Not Eating: How Long Is Too Long?](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-eating-how-long-too-long) - [Cat Hissing at New Kitten: How Long Will It Last?](/knowledge/veterinary-medicine/anxiety-and-behavior-support/cat-hissing-at-new-kitten) - [Vitamin B12 Injections for Cats: Cobalamin Deficiency and Dosing Schedule](/knowledge/veterinary-medicine/nutrition/vitamin-b12-injections-for-cats-cobalamin-deficiency-and-dosing-schedule) - [How Long Can A Healthy Cat Go Without Peeing](/knowledge/veterinary-medicine/symptom-guides/how-long-can-a-healthy-cat-go-without-peeing) - [Cat Not Pooping: How Long Is Too Long?](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-pooping-how-long-too-long) ## References 1. [Glargine and protamine zinc insulin have a longer duration of action and result in lower mean daily glucose concentrations than lente insulin in healthy cats](https://pubmed.ncbi.nlm.nih.gov/18471141/). Journal of veterinary pharmacology and therapeutics, 2008. 2. [Management of diabetic cats with long-acting insulin](https://pubmed.ncbi.nlm.nih.gov/23522171/). The Veterinary clinics of North America. Small animal practice, 2013. 3. [Loose-control of diabetes mellitus with protamine zinc insulin in cats: 185 cases (2005-2015)](https://pubmed.ncbi.nlm.nih.gov/30992596/). The Canadian veterinary journal = La revue veterinaire canadienne, 2019. 4. [Efficacy of protamine zinc insulin for treatment of diabetes mellitus in cats](https://pubmed.ncbi.nlm.nih.gov/11149712/). Journal of the American Veterinary Medical Association, 2001. ## Further Reading - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners) - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information)