ProZinc Insulin for Dogs and Cats: Shared Use and Differences

Name: ProZinc Insulin for Dogs and Cats: Shared Use and Differences
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-02

ProZinc insulin for dogs and cats is a protamine zinc insulin (PZI) product approved by the FDA for use in both species, which makes it unusual among veterinary insulins. The dose, monitoring plan, and expectations for remission differ between dogs and cats, so the same bottle is used very differently depending on which pet is in front of your veterinarian. This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

ProZinc is a protamine zinc insulin, a long-acting formulation that is FDA-approved for both dogs and cats.
Cats often start at about 0.25 U/kg (roughly 1 U per cat) twice daily, and PZI is one of the most common insulins used in newly diagnosed feline diabetics [1].
Dogs are usually started on NPH or lente insulin instead of PZI, so ProZinc is a less typical first choice in dogs even though it is approved for them [1].
Never change the dose on your own. Your veterinarian sets the starting dose and adjusts it based on glucose curves, clinical signs, and sometimes fructosamine levels [2].
Store insulin carefully. Extreme heat, freezing, and vigorous shaking can damage it, and expired insulin should never be used [3].

What ProZinc Is and What Veterinarians Use It For

ProZinc is a protamine zinc insulin, often shortened to PZI. The "protamine zinc" part refers to two ingredients that slow the absorption of insulin after injection, which stretches its effect over many hours instead of peaking quickly. That slower profile is what makes it useful for managing diabetes mellitus, a condition in which the body cannot properly produce or respond to insulin, leading to high blood glucose [4].

In cats, PZI is one of the two most commonly used insulins for newly diagnosed diabetes, alongside insulin glargine. Both produce comparable glycemic control and remission rates [1]. A clinical trial of 67 diabetic cats treated with PZI twice daily for 45 days found significant decreases in mean blood glucose and serum fructosamine concentrations over the treatment period, which supports its use as a maintenance insulin [2].

In dogs, the picture is different. The standard initial insulins for canine diabetes are NPH or lente, started at 0.25 to 0.5 U/kg under the skin every 12 hours [1]. Most dogs need two injections per day, timed with two equal-calorie meals given right before each injection [1]. ProZinc is approved for dogs, and some veterinarians use it when a dog does not respond well to the usual choices, but it is not the typical first-line insulin. If your dog is on ProZinc, your veterinarian had a specific reason, and that plan should be followed exactly.

How ProZinc Works

Insulin is the hormone that unlocks the door to your pet's cells. It attaches to cells and signals when to absorb glucose from the blood, which lowers blood glucose while feeding the muscles, liver, and fat [4]. In diabetes, that system breaks down. In Type I diabetes, the pancreas does not make enough insulin. In Type II diabetes, the body's cells do not respond properly to insulin. Either way, glucose builds up in the blood while cells starve for fuel [4].

Protamine zinc insulin works by releasing insulin slowly after injection. In healthy cats, PZI has a measurable onset of action, a time to lowest glucose (nadir), and a duration of action that researchers have tracked with glucose monitoring [5]. That slow release is why PZI is usually given twice daily instead of once. It also explains why a single blood glucose reading right after an injection tells you very little. The interesting numbers come hours later, when the insulin is near its peak effect.

Dosing Basics for Dogs and Cats

Who decides the dose

Your veterinarian does. Doses are calculated from your pet's body weight, current glucose levels, other health conditions, and how your pet responded to previous insulin. In cats, a common starting point is 0.25 U/kg, which often works out to about 1 unit per cat, given under the skin every 12 hours [1]. In dogs, the typical starting range for NPH or lente is 0.25 to 0.5 U/kg every 12 hours [1]. Your veterinarian will tell you the exact number for your pet and will adjust it over time.

How it is given

ProZinc is injected under the skin, usually in the scruff or along the side of the body, using a U-40 syringe matched to the insulin concentration. Matching the syringe to the insulin type matters because different insulins come in different strengths and units [3]. Giving the wrong syringe can deliver the wrong dose. Your veterinary team will show you how to draw up the dose, where to inject, and how to rotate injection sites.

Feed your pet before the injection, not after. In dogs, two meals of equal calories are given, each one immediately before insulin administration [1]. If your pet does not eat, call your veterinarian before injecting, because giving insulin to a pet with an empty stomach raises the risk of low blood sugar.

What to do about a missed dose

If you miss a dose, do not double up. Call your veterinarian or an emergency clinic for instructions specific to your pet. In general, a missed dose is safer than a double dose, because too much insulin can cause dangerous hypoglycemia. Keep a simple log of every injection, including the time and the dose, so you and your veterinarian can spot patterns.

Monitoring differs between species

Cats and dogs are monitored differently. Cat owners are more likely to use home blood glucose monitoring than dog owners, and more cat owners report satisfaction with the diabetic control they achieve [6]. Your veterinarian may ask you to check glucose at home, bring your pet in for a glucose curve, or both. Serum fructosamine, a marker of average glucose over the previous couple of weeks, is another tool, and it was used alongside glucose curves in the PZI trial in cats [2]. For a deeper look at how these tests fit together, see Monitoring Endocrine Therapy in Veterinary Patients: Insulin and Beyond.

Diet matters too. In one long-term study of 185 cats treated with PZI, a low-carbohydrate diet was significantly associated with longer survival time [7]. Most pets in a large owner survey were not fed a prescribed diabetes diet, which suggests many owners never get clear diet guidance [6]. Ask your veterinarian what to feed, and ask whether a prescription diet is right for your pet.

Side Effects of ProZinc in Dogs and Cats

Side effect	How common or serious	What to do
Hypoglycemia (low blood sugar): weakness, wobbling, confusion, seizures	Uncommon but serious. In one transition study, hypoglycemia appeared in about 16% of 12-hour glucose readings, and 5 cats had clinical signs [8]	If signs are mild, offer food and call your veterinarian. If your pet is unsteady, seizing, or unresponsive, treat as an emergency
Injection site reactions (soreness, swelling, hair loss)	Uncommon, usually mild	Rotate sites and tell your veterinarian at the next visit
Poor glucose control (high blood sugar persists)	Common early on, since doses often need adjustment	Log signs and glucose readings, and ask about a dose change or a different insulin
Short duration of action (glucose rises too early between doses)	Recognized in cats. In one study, 6 of 19 cats had short duration on their previous insulin, and all 6 improved to at least 9 hours on PZI [8]	Report early-morning high readings to your veterinarian
Allergic reaction (facial swelling, hives, trouble breathing)	Rare but serious	Stop and seek emergency care right away

Some cats achieve remission, meaning they no longer need insulin. In one study of 185 cats on PZI, remission probability was 56.2%, and lower mean glucose, lower mean insulin dose, and recent pre-diabetic corticosteroid use increased the odds of remission [7]. Another study reported remission in about 23% of cats transitioned to a human recombinant PZI product [8]. Remission is possible but not guaranteed, and it is more likely with good control and consistent monitoring.

Who Should Not Take It and Drug Interactions

ProZinc is not right for every diabetic pet. Pets with certain concurrent conditions, pregnant or breeding animals, and pets with a history of reactions to insulin products may need a different plan. Your veterinarian will review your pet's full history before prescribing.

Drug interactions matter. Glucocorticoids and progestins can cause insulin resistance and secondary diabetes in dogs, and pregnancy and diestrus can predispose animals to diabetes [1]. That means steroids given for allergies, skin disease, or other conditions can work against insulin. If another veterinarian prescribes a steroid, tell them your pet is diabetic. For a full review of how other medications interact with insulin, see Drug Interactions with Antidiabetic Medications in Dogs and Cats.

Obesity predisposes both dogs and cats to insulin resistance [1], so weight management is part of treatment, not an optional extra. If your dog is on a different insulin, the canine protocol is covered in NPH Insulin Dogs Dose: Canine Diabetes Twice Daily Protocol.

Overdose and When to Call for Help

An insulin overdose can cause life-threatening hypoglycemia. Signs include weakness, staggering, tremors, seizures, collapse, and unresponsiveness. If you think your pet received too much insulin, call your veterinarian or an emergency clinic immediately. If your pet is already showing neurologic signs, go to the nearest emergency hospital now.

If your pet is alert and able to swallow, your veterinarian may advise offering food. Do not try to force food or liquid into a pet who is unconscious or seizing. Do not wait to see if signs develop on their own, because hypoglycemia can worsen quickly.

For poison-related questions, the ASPCA Animal Poison Control Center is available at (888) 426-4435, and the Pet Poison Helpline is available at (855) 764-7661. These services may charge a consultation fee.

Storage and Handling

Insulin is fragile. It must be stored carefully, not too cold and not too hot, and even shaking it too vigorously can harm the medication [3]. Some insulins need to be rolled gently between your hands instead of shaken. Never use insulin past its expiration date [3].

Follow the storage instructions that come with your specific bottle, and ask your veterinary team to walk you through handling and syringe use when you pick up the prescription [3]. Keep a spare bottle on hand if your veterinarian recommends it, since running out can mean missed doses. Write the date you opened the bottle on the label, because opened insulin has a limited shelf life.

Limitations and When to Contact a Veterinarian

ProZinc works well for many pets, but it is not a cure, and every pet responds differently. Some cats go into remission, many do not, and dogs almost always need lifelong insulin. Individual cases need a veterinarian who knows your pet's history, so use the guidance below as a starting point for a conversation, not a replacement for one.

Contact your veterinarian the same day if your pet vomits, refuses to eat, has diarrhea, or seems more tired than usual. These can be early signs of a problem with glucose control or another illness. Call right away if you miss a dose, run out of insulin, or notice a change in your pet's water intake or urination.

Go to an emergency clinic now if your pet is weak, wobbly, having tremors or seizures, breathing hard, or unresponsive. These are signs of severe hypoglycemia or another emergency. Do not wait for a regular appointment.

Schedule a routine visit if your pet's glucose readings are consistently high or low, if you see early-morning highs that suggest the insulin is wearing off too soon, or if you are struggling with the injections. Your veterinarian can adjust the dose, change the insulin, or switch you to a different monitoring plan.

Frequently Asked Questions

Is ProZinc approved for both dogs and cats?

Yes. ProZinc is FDA-approved for use in both species, which is uncommon for veterinary insulins. That said, PZI is a more typical choice in cats, while dogs are usually started on NPH or lente insulin [1]. Your veterinarian will decide whether ProZinc fits your pet.

How often is ProZinc given?

It is usually given twice daily, about 12 hours apart, under the skin. In cats, the common starting dose is 0.25 U/kg, often about 1 unit per cat, every 12 hours [1]. Most dogs also need two insulin doses per day [1]. Your veterinarian will set the exact schedule.

Can my cat go into remission on ProZinc?

Remission is possible. In one long-term study of cats treated with PZI, the remission probability was 56.2%, and factors like lower mean glucose, lower insulin dose, and a low-carbohydrate diet were linked to better outcomes [7]. Not every cat remits, and remission is not the same as a cure. Your cat will still need monitoring.

What should I do if my pet's blood sugar is low?

If your pet is alert, offer food and call your veterinarian right away. If your pet is wobbly, seizing, or unresponsive, go to an emergency clinic immediately. Do not wait to see if the signs pass, because hypoglycemia can become life-threatening quickly.

Can I switch my pet from another insulin to ProZinc on my own?

No. Insulin changes must be managed by your veterinarian, often with a structured transition plan and close glucose monitoring. In one study, cats transitioning to a human recombinant PZI product were switched using a nadir-led protocol, and the change was linked to improved clinical signs and quality of life [8]. Your veterinarian will design a safe plan for your pet.

References

Diabetes Mellitus in Dogs and Cats - Endocrine System. Merck Veterinary Manual.
Efficacy of protamine zinc insulin for treatment of diabetes mellitus in cats. Journal of the American Veterinary Medical Association, 2001.
Managing canine diabetes. Cornell University College of Veterinary Medicine.
Feline Diabetes. Cornell University College of Veterinary Medicine.
Comparison of the pharmacodynamics of protamine zinc insulin and insulin degludec and validation of the continuous glucose monitoring system iPro2 in healthy cats. Research in veterinary science, 2018.
Owner experiences in treating dogs and cats diagnosed with diabetes mellitus in the United States. Journal of the American Animal Hospital Association, 2014.
Loose-control of diabetes mellitus with protamine zinc insulin in cats: 185 cases (2005-2015). The Canadian veterinary journal = La revue veterinaire canadienne, 2019.
Prospective evaluation of a protocol for transitioning porcine lente insulin-treated diabetic cats to human recombinant protamine zinc insulin. Journal of feline medicine and surgery, 2018.