Cat Insulin Calculator
Veterinary review by Gabriel A. Sánchez Barreras, DVM — September 2026
Estimate a conservative starting insulin dose for a diabetic cat from its body weight, for educational reference alongside your veterinarian.
Cats are not small dogs, and feline diabetes departs from the canine version in ways that change dosing from the first injection.
The most consequential difference is that cats can go into remission. With early, effective glucose control and a low-carbohydrate diet, a meaningful proportion stop needing insulin altogether — something that essentially does not happen in dogs. That possibility rewards careful early management and makes overdosing costly in a way that goes beyond immediate risk.
Starting doses in cats are also strikingly small and often flat rather than weight-scaled: many protocols begin at one to two units twice daily almost regardless of body weight, because feline insulin sensitivity varies enormously and the consequences of starting too high are severe.
Then there is the syringe trap. Several veterinary insulins are U-40, not the U-100 used in human medicine. Drawing U-40 insulin into a U-100 syringe delivers roughly two and a half times the intended dose — a well-documented cause of fatal hypoglycemia in pets.
The calculator below gives a conservative starting estimate for discussion with your vet. Beneath it you will find a weight chart, the critical safety points, and how feline diabetes is monitored.
How to Use This Calculator
- Enter your cat's weight in kilograms or pounds (use the toggle).
- Choose a starting dose factor — 0.25 units/kg is the common conservative start.
- Read the estimate: the per-injection dose (given twice daily, every 12 hours) and the daily total.
Treat this as a ballpark for discussion. Many vets cap the initial dose near 1–2 units per injection and round down, then fine-tune from a glucose curve. Never start or change insulin without your veterinarian.
How Cat Insulin Dosing Works
Most diabetic cats are treated with a long-acting insulin — commonly glargine or PZI — given twice daily (every 12 hours) with food. A typical conservative starting point is about 0.25 units per kilogram per injection, but vets deliberately start low and increase slowly, because cats are small and a small absolute error is a large relative dose.
Example: a 5 kg cat → 5 × 0.25 = 1.25 units per injection, about 2.5 units total per day. Many clinicians round this down to 1 unit per injection to start.
The dose is then refined using a blood-glucose curve performed with your vet, not by formula. Some cats even achieve diabetic remission with early, careful insulin and diet changes.
🐾 Cat Insulin Starting-Dose Chart by Weight
Conservative starting estimates at 0.25 u/kg per injection, given twice daily. The last column shows the practical dose most vets actually start with — because many cap the initial dose at 1–2 units regardless of weight, then adjust from a glucose curve.
| Cat weight | Per injection (0.25 u/kg) | Daily total (×2) | Typical vet start (capped) |
|---|---|---|---|
| 2 kg / 4.4 lb | 0.5 u | 1.0 u | 0.5–1 u |
| 3 kg / 6.6 lb | 0.75 u | 1.5 u | 1 u |
| 4 kg / 8.8 lb | 1.0 u | 2.0 u | 1 u |
| 5 kg / 11 lb | 1.25 u | 2.5 u | 1–1.5 u |
| 6 kg / 13.2 lb | 1.5 u | 3.0 u | 1.5 u |
| 7 kg / 15.4 lb | 1.75 u | 3.5 u | 1.5–2 u |
| 8 kg / 17.6 lb | 2.0 u | 4.0 u | 2 u |
U-40 Units → mL (feline insulins like ProZinc & Vetsulin)
Many cat insulins are U-40 (40 units/mL), so 1 unit is a larger volume than with U-100. Always draw with a matching U-40 syringe.
Full conversion (U-40/U-100/U-500) on the Units to mL Calculator; how to read the barrel in the syringe guide. For dogs, see the Dog Insulin Calculator.
Critical Safety Points for Cat Owners
- Use the matching syringe. Many feline insulins are U-40, not U-100 — the wrong syringe causes a 2.5× dosing error. See our syringe guide.
- Feed with each dose. Insulin without food can cause dangerous hypoglycemia.
- Never "make up" a missed dose. Skip it and resume the normal schedule, per your vet.
- Keep corn syrup or honey on hand for signs of low blood sugar (weakness, wobbliness, seizures) and call your vet immediately.
Diabetes in Cats: Symptoms, Insulin Types & Diet
Common signs of feline diabetes
The classic signs are drinking and urinating much more, a big appetite with weight loss, and lethargy. A late sign is a flat-footed, "dropped-hock" hind-leg stance (plantigrade posture) from diabetic neuropathy. Any of these warrants a vet visit and a blood-glucose check.
Insulin types used in cats
The mainstays are PZI / protamine zinc insulin (ProZinc, a U-40 product licensed for cats) and glargine (Lantus, U-100); detemir is sometimes used. All are long-acting and given twice daily with meals. Match the syringe to the concentration — U-40 insulin needs a U-40 syringe.
Diet and the chance of remission
A low-carbohydrate, high-protein (typically canned) diet lowers insulin requirements. With early, careful insulin and diet changes, some cats reach diabetic remission and no longer need insulin — most likely in the first few months after diagnosis.
Frequently Asked Questions
How much insulin does a diabetic cat need?
A common conservative starting point is about 0.25 units per kg per injection, twice daily — so a 5 kg cat might start around 1–1.25 units per injection. Vets usually cap the initial dose near 1–2 units and then adjust using a glucose curve.
Which insulin is used for cats?
Long-acting insulins such as glargine or PZI (protamine zinc insulin) are most common for cats, given twice daily with food. Some feline insulins are U-40 concentration, so the correct U-40 syringe is essential.
Can I use human insulin doses for my cat?
No. Cat dosing, insulin type, and concentration differ from human therapy, and cats are far smaller. Only use the insulin, syringe, and dose your veterinarian prescribes.
How is the dose adjusted over time?
Through a blood-glucose curve done with your vet — measuring glucose across the day to see the lowest point (nadir) and duration. The dose is changed in small steps based on that curve, never by formula alone.
Can a diabetic cat stop needing insulin (go into remission)?
Yes. Some cats achieve diabetic remission and no longer need insulin, especially when good glucose control and a low-carbohydrate diet start soon after diagnosis. Remission is most likely in the first few months, but cats can relapse, so monitoring continues even after insulin stops.
What are the signs of low blood sugar in a cat?
Weakness, wobbliness or unsteady walking, disorientation, intense hunger, trembling, and in severe cases collapse or seizures. Rub honey or corn syrup on the gums and contact your vet or an emergency clinic immediately. Always feed with each insulin dose to reduce the risk.
Sources
- Behrend E, et al. "2018 AAHA Diabetes Management Guidelines for Dogs and Cats." J Am Anim Hosp Assoc. 2018.
- Insulin product labeling (glargine, PZI; U-40 / U-100 concentrations).
Written by Ryan Mitchell · Last updated: September 2026