ProZinc vs NPH insulin: what's the difference?
How ProZinc and NPH insulin compare: what each is for, how it works, side effects and cost, side by side.
Last updated: October 2026 · 4 sources · see sources
Side by side
| ProZinc | NPH insulin | |
|---|---|---|
| Generic name | Protamine zinc insulin | NPH insulin |
| Brand names | ProZinc | Humulin N, Novolin N |
| For | Dogs and cats | Dogs and cats |
| Prescription | Prescription | Prescription |
| Used for | An injectable insulin approved for diabetic cats and dogs. [1] | An intermediate-acting human insulin used mostly in diabetic dogs. [2] |
| How it works | It replaces insulin so the body can move sugar out of the blood. The added protamine and zinc make it last longer. [1] | Protamine is added so it acts longer than regular insulin. [2] |
| Common side effects | Lumps at injection sites. The main risk is low blood sugar. [1] | Skin lumps; low blood sugar is the main risk. [2] |
| Use with care | Signs of low blood sugar include weakness, wobbliness, trembling and seizures; call your vet right away. Don't inject if your pet isn't eating unless your vet says to. [1] | Use only the syringe type your vet prescribes (U-100). Signs of low blood sugar need urgent care. [2] |
| Typical price | Insulin for a dog (any type): $30–$150 a month [3] Insulin for a cat (any type): $50–$150 a month [4] | Insulin for a dog (any type): $30–$150 a month [3] Insulin for a cat (any type): $50–$150 a month [4] |
| Full guide | ProZinc (PZI insulin) guide | NPH insulin (Humulin N, Novolin N) guide |
Key differences
On the basics they are alike: same kind of animal, same way to get them. The differences are in how they work and what else they cover, shown in the table above.
Which one is right for my pet?
That is a call for your vet. They weigh your pet's age, weight, other health problems, other medicines and what you can realistically give at home.
Switching from ProZinc to NPH insulin is common, but do it only with your vet's plan.
Common questions
What is the difference between ProZinc and NPH insulin?
Both are insulins. NPH is a human insulin used mostly in dogs; ProZinc is approved for cats and dogs.
Is ProZinc better than NPH insulin?
Neither is better for every pet. Your vet chooses based on your pet's species, age, health history, other medicines and what you can manage at home.
Can my pet take ProZinc and NPH insulin together?
Only if your vet says so. Some medicines in the same family should not be combined, and others are often used together. Always check before adding or switching.
Do ProZinc and NPH insulin need a prescription?
ProZinc: Yes. It needs a prescription from a veterinarian. NPH insulin: Yes. It needs a prescription from a veterinarian.
How much do ProZinc and NPH insulin cost?
ProZinc: Insulin for a dog (any type) $30–$150 a month. NPH insulin: Insulin for a dog (any type) $30–$150 a month. Prices vary by pet size, pharmacy and clinic.
Related
This page is general information for planning, not veterinary advice. Talk to your vet about your own pet.