Diabetic cat: insulin, Bexacat or Senvelgo? Questions to ask

Let me guess. Your cat has been drinking out of every glass you leave on the nightstand, the litter box looks like someone's been hiding snowballs in it, and he's yelling for breakfast an hour early while somehow getting thinner. Then the bloodwork came back, and now you have a diabetic cat. And just when you were bracing yourself for needles, your vet mentioned there's also a once-a-day pill, or a liquid.

Take a breath. Let's walk through it the way I would if you were sitting across from me.

Being a diabetic cat's person used to mean one road: insulin shots. Now there are three: insulin, Bexacat and Senvelgo. They're not interchangeable, and the newer two come with real warnings. Here's how I'd lay them out.

Diabetes in cats, in plain words

Insulin is the hormone that lets the body's cells pull sugar out of the blood and use it for fuel. In a diabetic cat, that isn't working. Either the pancreas isn't making enough insulin, or the cells have stopped listening to it. Sugar piles up in the blood and spills into the urine, dragging water with it. That's the thirst, the big clumps and the hungry, thinning cat.

Here's the catch that shapes everything below. Both labels' owner sheets say it: there's no test that tells your vet whether your cat still makes enough of his own insulin. Some cats start out with cells that don't listen, then slowly lose their own insulin over time.

The three options at a glance

• Insulin shots. The classic. A shot under the skin, usually twice a day, about 12 hours apart. Two veterinary insulins are approved for cats, and human insulins such as glargine are commonly used too.
• Bexacat (bexagliflozin). A flavored tablet given once a day. For cats that weigh at least 6.6 pounds.
• Senvelgo (velagliflozin). A liquid given once a day, straight into the mouth or on a small amount of wet food.

Bexacat and Senvelgo belong to a newer group of drugs called SGLT2 inhibitors. They are not insulin. As the FDA explains, they lower blood sugar by having the kidneys pass more sugar out in the urine. They don't help the cells use sugar the way insulin does. That difference is why the rules for them are so strict.

Who can take Bexacat or Senvelgo

Both labels say these drugs are for otherwise healthy cats whose diabetes has never been treated with insulin. They should not be used in:

• A cat who's had insulin before, or is on it now. The labels tie this to a higher risk of ketoacidosis and death. In the Senvelgo study, 12 of the 38 cats who'd been on insulin before (32%) developed ketones or ketoacidosis in the first week.
• A cat who's sick at diagnosis. If he's not eating, dehydrated or lethargic when he's diagnosed, the labels say not to start.
• A cat whose own insulin has run out (insulin-dependent diabetes).
• A cat who hasn't been screened. Both labels call for testing first, and each has its own list of problems that rule it out. Bexacat's includes liver disease and reduced kidney function. Senvelgo's includes recent pancreatitis and certain kidney and liver values.

The 2025 iCatCare guidelines for cat diabetes put it in one phrase: these drugs are for the "happy diabetic," a cat who's diabetic but otherwise doing well.

The label warnings, in plain words

Both drugs carry a boxed warning, printed at the very top of the label. Here's what it says, without the jargon.

Ketoacidosis, sometimes with normal blood sugar. When the body can't use sugar, it burns fat instead and makes acids called ketones. Too many, and the blood turns acidic. That's diabetic ketoacidosis (DKA), and it can kill. With these drugs, it can happen while the blood sugar reading looks normal. The labels call that euglycemic DKA. It means a normal glucose number doesn't prove your cat is fine.

• In the Senvelgo study of 252 cats, 18 (7.1%) developed DKA or euglycemic DKA. All but 5 of those happened within the first 2 weeks.
• In the main Bexacat study of 84 cats, 3 developed DKA and 2 developed euglycemic DKA.
• The iCatCare guidelines estimate euglycemic DKA in about 1 in 15 newly diagnosed cats started on one of these drugs, and about 1 in 10 cats who'd had insulin before.

Deaths. Neither label hides this. In the Senvelgo study, 13 deaths or euthanasias were considered possibly related to the drug or to declining diabetes control. In the main Bexacat study, 3 of 84 cats died or were euthanized. In a longer Bexacat follow-up study of 125 cats, 20 had serious reactions that all ended in death or euthanasia, from ketoacidosis, fatty liver and other causes.

More on the Bexacat label. It also warns that long-term use may raise the risk of a bladder cancer called urothelial carcinoma (2 cats in that follow-up study), and that it can raise blood calcium, which can lead to calcium bladder stones. Bexacat's label also says it may raise the risk of urinary tract infections, and both labels have cats screened and watched for them.

Common side effects. In the field studies, Senvelgo's most common were diarrhea or loose stool (about half the cats), weight loss and vomiting. Among the signs an owner would see, vomiting, diarrhea and loss of appetite led Bexacat's list.

The stop-and-call rule. This is the one to tape to the fridge. Both owner sheets say to stop the drug and contact your vet right away if your cat shows less interest in food or stops eating, has less energy or a change in normal activity (like hiding or grooming less), vomits or has diarrhea, or is weak or has trouble walking or standing.

Here's the thing: none of that means these drugs are bad. In the field studies, Bexacat counted as a success in about 83% of cats at 8 weeks, and Senvelgo in about 88% at 30 days. The iCatCare guidelines call them effective in around 80 to 90% of cats, and a real option that can spare a cat the shots. It means the right cat, close watching, and a fast phone call.

Bexacat vs Senvelgo: how the two differ

They work the same way and carry the same boxed warning. The differences are mostly practical:

• Form. Bexacat is a flavored tablet. Senvelgo is a liquid with a measuring syringe, and it can go on a small amount of wet food.
• Size. Bexacat is for cats who weigh at least 6.6 pounds. Senvelgo is measured by your cat's weight.
• The first checkups. Senvelgo's owner sheet asks for two vet visits in the first week, around day 2 or 3 and again around day 7, even if your cat seems fine, to check for ketones. Bexacat's label sets rechecks at 2, 4 and 8 weeks. The iCatCare guidelines suggest checks at the end of weeks 1, 2 and 4 for either drug.
• The screening lists differ a little, as above.

Which is better? There's no head-to-head answer in the labels. The better one is the one your cat will actually take, that fits his health and your vet's screening, and that you can monitor closely in those first weeks.

Insulin for cats

Insulin is still the standard, and for many cats it's the right choice: any cat who's sick at diagnosis, who's had insulin before, or who isn't a good fit for the pills.

• Most cats get it twice a day, about 12 hours apart. The iCatCare guidelines say most insulins used in cats need at least two shots a day to work best.
• Low blood sugar is the risk to know. The iCatCare guidelines list wobbling, trembling, unusual tiredness, vomiting and seizures as the usual signs. Keep corn syrup or honey next to the insulin, and ask your vet exactly what to do with it.
• Food and the shot. I always make sure they eat first, before the insulin. You want to know whether they're going to eat the full meal before that shot goes in. The newest cat guidelines say that for some cats, such as grazers or cats on low-carbohydrate food, the shot doesn't have to wait for the meal. Every vet's a little different, so ask yours how they want you to do it.
• Remission is possible. Some cats stop needing insulin, at least for a while. The iCatCare guidelines link a better chance of it to getting good control early, weight loss in overweight cats, and a low-carbohydrate wet food. Studies comparing two insulins often used in cats, PZI and glargine, found similar remission rates. Remission on the SGLT2 drugs isn't well studied yet.

Given the choice, I'd go with a stick-on glucose sensor for monitoring. I use the FreeStyle Libre. Your cat is at home and more comfortable, and isn't getting stuck every two hours for a glucose curve. The catch: in cats, sensors can be a little more difficult and finicky. The iCatCare guidelines say they often last only about 5½ to 10 days on a cat.

Which is right for my cat?

It depends on your cat, his health on the day he's diagnosed, and what's going on in your household. A twice-a-day shot schedule works beautifully for some families and not at all for others. A once-a-day pill or liquid can be easier to fit into the day, but it comes with stricter screening and closer watching in the first weeks.

For an otherwise healthy cat who's newly diagnosed, there are three options: Bexacat, Senvelgo and insulin. Your vet can go over the positives and negatives of each with you.

Whatever you choose, ask your vet about planned procedures too. Both pill labels suggest your vet may pause them around surgery or any time your cat is eating less, so mention any dental or surgery that's coming up. And if you're ever unsure about a dose, a late dose or a double one, call.

Between daily doses, appetite checks, the early rechecks and the lab results, there's a lot to keep straight. Honestly, that's why I built WagNote (full disclosure: it's my app). I kept seeing owners struggle to keep track of everything with conditions like this, so I put it all in one place.

If you do one thing this week: write down your cat's normal. How much he eats, how much he drinks, how he greets you at the door. On any of these treatments, a change from normal is your early warning. Your cat will pretend not to notice you watching. He'll notice.