High blood sugar in dogs: what it means, the signs, and when it's an emergency

My dog's blood sugar seems high. What do I do?

First, look at him, not just a number. Is he eating, drinking his usual amount, alert and himself? Then a high spell usually isn't an emergency.

If he seems himself, give his meals and insulin as your vet has set them. Write down what you saw: any reading you took, how much he's drinking and peeing, and anything different about his day. Tell your vet at the next check, or sooner if it keeps happening. My meter shows a number. What should I do? covers single readings.

If he's vomiting, won't eat, is unusually tired or weak, is breathing fast or deep, or his breath smells sweet, call your vet now. These can be signs of diabetic ketoacidosis, a serious complication that needs hospital care. The emergency page has what to tell them.

Either way, don't give extra insulin and don't change his dose yourself. If you're not sure a shot went in, don't give another. What if we might have given the insulin twice? explains why.

Cooper's sugar runs high. What does high mean?

High blood sugar is what diabetes is. A diabetic dog's body doesn't make enough insulin, so the sugar from his food stays in his blood instead of being used. Insulin shots bring it down, but finding the dose that suits him takes time, and even then his sugar won't sit at one level all day.

Vets accept that a diabetic dog will have occasional high spells. What they look at is whether his signs are controlled: is he drinking, peeing and eating normally, and is his weight steady? That's why one glucose number on its own tells you little, and why thirst and energy matter as much as any reading.

Readings also move with his day. A change in routine, a stressful outing or a trip to the clinic can push a reading up for a while.

Signs of high blood sugar in dogs

The signs of high blood sugar are the same ones that usually lead to a diabetes diagnosis.

He drinks much more than usual and keeps asking for refills. Why is my diabetic dog drinking so much? goes into this.

He pees more, leaves bigger puddles, or has accidents indoors when he usually doesn't.

He's hungry all the time but still loses weight. See my diabetic dog is losing weight.

Over weeks and months, urine infections can keep coming back, and his eyes can turn cloudy from diabetic cataracts. Could a urine infection be part of this?

If these signs come back after his diabetes was under control, tell your vet. It usually means something has changed: the insulin, his food, or another illness.

Why a diabetic dog's sugar runs high

When a dog on insulin keeps running high, vets usually work through a few likely causes.

The insulin itself. Insulin that's been stored wrongly, is out of date or looks different from usual, the wrong syringe for that insulin, or a shot that didn't fully go in. Handling slips happen to everyone, so it's worth asking your vet to watch you give one. See storing insulin.

Food and treats. Extra food, a change of food, or treats he isn't used to. Steady meals, treats and walks at the same times each day make his insulin easier to get right. Treats for a diabetic dog has more.

Another illness. Infections, dental disease, pancreatitis, hormone problems such as Cushing's disease or an underactive thyroid, and some medicines, including steroids, can all make insulin work less well.

Stress. Fireworks, guests, a house move or a vet visit can raise his sugar for a while. Can fireworks, guests or a house move upset his diabetes?

A high after a low. Sometimes a dog's sugar swings high after it has dropped too low. When vets see this, they lower the dose, not raise it, which is another reason never to add insulin because of a high reading. What is the Somogyi rebound?

If his sugar stays high even on insulin, glucose stays high even on insulin goes through what your vet may check next.

When high blood sugar becomes an emergency

A diabetic dog whose sugar runs high but who is eating and himself is not usually in danger that day. The danger is diabetic ketoacidosis, often called DKA.

DKA happens when there isn't enough insulin working. His body starts breaking down fat for fuel instead, and acids called ketones build up in his blood. It's a life-threatening complication, and it needs treatment in hospital.

The signs: vomiting, not eating, being very tired, weak or low, breathing fast, deep or with effort, and breath that smells sweet, often alongside even more drinking and peeing than usual. They can be subtle at first. Vomiting, not eating, weakness, fast breathing or sweet breath in a diabetic dog is each a reason to call your vet now.

DKA is more likely when something else is going on, such as an infection, pancreatitis or another illness, or when he isn't getting enough insulin or isn't eating. A diabetic dog who stops eating is always a reason to call your vet. My diabetic dog ate only part of the meal covers smaller lapses.

If you have urine strips at home, a strip that shows ketones is a reason to call your vet straight away. But a dog who seems unwell needs the vet whatever the strip says.

How to lower a dog's blood sugar quickly

You don't, at home. There's no safe home trick for bringing a dog's sugar down fast, and trying it with extra insulin risks a dangerous low.

Extra insulin can drop his sugar too far, and a low can come on fast and become an emergency of its own. So don't give extra insulin or raise his dose on your own, even after a high reading. Low blood sugar in dogs explains why a dog whose sugar runs high can still go low.

What helps is being steady: the same meals at the same times, insulin given the way your vet showed you, his usual walks, and a note of what you see. If his sugar keeps running high, your vet may change his insulin, look for another illness, or ask for a glucose curve to see how his whole day goes.

If you're worried today, call your vet. If he seems unwell, go back to the steps at the top of this page.

What to tell your vet

Before you call or go in, jot down when he last ate and how much, when he last had insulin and whether you're sure it went in, how much he's drinking and peeing compared with usual, any vomiting or change in energy, and any readings you have.

Home testing, glucose curves and notes for your vet has a simple way to keep these notes, and questions about vet care helps you get ready for the visit.