Yes, 8 units of insulin per dose is a lot for a cat. Most diabetic cats need between 0.5 and 3 units per dose given twice daily, and veterinary guidelines define insulin resistance as any dose exceeding 6 units per injection. At 8 units, a cat is well into that resistant range, which usually signals either an underlying medical condition or a problem with how the insulin is being absorbed or administered.
What a Normal Dose Looks Like
Regardless of insulin type, cats typically start at 1 to 2 units per injection, given twice a day. Very small cats under about 4.5 pounds may start at just half a unit. Larger cats, even those over 9 pounds, rarely begin at more than 2 units. The dose is then adjusted upward gradually, usually by 1 unit at a time every two to four weeks, based on blood glucose monitoring and how the cat is doing at home.
The starting range in clinical guidelines is 0.25 to 0.5 units per kilogram of body weight. For context, a typical 10-pound cat (about 4.5 kg) would start somewhere between 1 and 2.25 units per dose. Even after weeks or months of adjustment, the vast majority of diabetic cats stabilize on doses in the 0.5 to 3 unit range. Reaching 8 units is uncommon and warrants investigation.
Why 6 Units Is the Red Flag
Veterinary endocrinologists generally consider a cat insulin-resistant when it needs more than 1.5 units per kilogram of body weight, or more than 6 units per dose, whichever comes first. At 8 units, a cat has clearly crossed that threshold. This doesn’t mean the insulin is harming the cat, but it does mean the insulin isn’t working as efficiently as it should, and there’s likely a reason why.
Insulin resistance means the cat’s body is fighting the effect of the insulin. The hormone is getting in, but something is blocking it from lowering blood sugar the way it normally would. Rather than simply increasing the dose further, your veterinarian will typically look for what’s causing the resistance in the first place.
Conditions That Drive Up Insulin Needs
Two conditions are especially common culprits when a cat’s insulin dose keeps climbing without adequate blood sugar control.
Acromegaly is a hormonal disorder caused by a growth hormone-producing tumor in the pituitary gland. It’s more common in cats than many owners realize, and it makes the body increasingly resistant to insulin. Cats with acromegaly often stay thirsty, hungry, and urinate excessively despite receiving doses that would normally be more than enough. Some of these cats eventually need 15 or even 20 units before the condition is identified.
Hyperadrenocorticism (Cushing’s disease) causes the body to overproduce cortisol, which directly counteracts insulin. In most cats, this condition is actually discovered because the diabetes proves difficult to control. Once the excess cortisol is addressed, insulin needs often drop dramatically, and some cats can stop insulin entirely.
Other factors that can push doses higher include chronic infections, inflammatory conditions, obesity, and certain medications like corticosteroids. Even something as simple as using expired insulin or storing it improperly can make it less effective, creating the appearance of resistance when the real problem is the insulin itself.
The Risk of Rebound Hyperglycemia
One important trap with high insulin doses is a phenomenon called rebound hyperglycemia, sometimes called the Somogyi effect. Here’s what happens: a large dose of insulin drives blood sugar dangerously low, often while the cat is sleeping or when you aren’t watching closely. The body then panics and dumps stored sugar into the bloodstream, causing blood glucose to spike far above normal levels. When you check the cat’s blood sugar later, it looks sky-high, which can make it seem like the dose needs to go even higher.
This creates a vicious cycle. The dose goes up, the crash gets worse, the rebound gets bigger, and blood sugar readings keep looking terrible. In the original research describing this in cats, blood sugar would drop below 70 mg/dL within hours of an injection, then shoot above 370 mg/dL and stay elevated for up to 24 hours. The only way to catch it is with a blood glucose curve, where levels are checked every few hours across an entire dosing cycle, rather than relying on a single reading.
Signs of Too Much Insulin
Hypoglycemia, or dangerously low blood sugar, happens when glucose drops to 60 mg/dL or below. The signs progress in severity and can move quickly:
- Early signs: unusual hunger, restlessness, shivering, or simply becoming very quiet and refusing food
- Moderate signs: wobbling, poor coordination, disorientation
- Severe signs: seizures, convulsions, loss of consciousness
Early signs can be subtle. Some cats don’t show the classic shaking or wobbling. They just become unusually still and stop eating. If your cat is on a high dose like 8 units, keeping corn syrup or honey on hand is a practical safety measure. Rubbing a small amount on the gums can buy time during a hypoglycemic episode while you contact your vet.
How Diet Can Lower Insulin Needs
Switching to a low-carbohydrate diet is one of the most effective ways to reduce a cat’s insulin requirements, and the research behind it is striking. In one study, every single cat on a low-carb canned diet needed its insulin dose reduced, and a third were able to stop insulin completely. A larger study of 63 diabetic cats found that 68% of those eating a low-carbohydrate, low-fiber diet could discontinue insulin over four months, compared to 41% on a moderate-carb, high-fiber diet.
Many commercial cat foods, especially dry kibble, are very high in carbohydrates. For a diabetic cat on 8 units of insulin, diet is one of the first things worth examining. A switch to a high-protein, low-carbohydrate wet food can sometimes make a dramatic difference in how much insulin the cat actually needs. This kind of change should be coordinated with your vet, because as insulin needs drop, the existing dose can suddenly become too high.
What to Discuss With Your Vet
If your cat is on 8 units per dose and blood sugar still isn’t well controlled, a few specific questions are worth raising. Has the cat been screened for acromegaly or Cushing’s disease? Has a full blood glucose curve been done to rule out rebound hyperglycemia? Is the insulin being stored and administered correctly, with properly mixed suspensions and fresh cartridges? And has diet been optimized for low carbohydrate content?
Some cats on high doses are actually reasonably well controlled, with blood glucose consistently between 200 and 400 mg/dL and minimal symptoms at home. In those cases, the dose may be appropriate for that individual cat, even if it’s above the typical range. The concern isn’t the number itself so much as whether the number is working, and whether something treatable is driving it higher than it needs to be.