Diabetic Comas in Dogs

Diabetes mellitus is a type of endocrine disease that affects the pancreas. The pancreas is responsible for the production of a hormone called insulin, which helps to bring blood sugar or glucose into the body’s cells for nutrition. When there are insufficient levels of insulin in the blood, or if the body becomes resistant to insulin, too much glucose is left in the bloodstream and diabetes occurs.

When dogs develop diabetes, they need to have insulin provided to them via a needle and syringe. Most insulin treatments are given on a twice daily basis to help maintain adequate levels of glucose in the blood and to help bring glucose into cells. Without insulin, the cells become starved, and the body receives a signal to eat and drink more. It is important to seek to control glucose levels as quick as possible. Otherwise, dogs can become severely dehydrated, lose weight, and in severe cases, can develop seizures or fall into a coma.

What is a diabetic coma?

A diabetic coma is when a diabetic dog’s mentation (aka sense of self and awareness of surroundings) is greatly diminished due to the presence of high levels of glucose in the blood stream. Most patients with diabetes mellitus will have clinical signs that are noticeable, that would prompt a trip to the vet’s office for an exam and diagnostics. Dogs with diabetes tend to drink a lot, but this is because they lose a lot of water through their urine due to the presence of too much glucose in the blood.

At high levels, glucose spills over into the urinary bladder from the kidneys. Glucose attracts a lot of water which is why pets with diabetes urinate more than normal. If there are other signs of illness like vomiting and diarrhea, untreated diabetic dogs can get very dehydrated, especially if they stop drinking due to tummy upset. This creates a hyperosmolar hyperglycemic state, which basically means that the concentration of sugar in the blood is extremely high. When the brain becomes affected by this, it can alter a dog’s state of consciousness. Coma is extremely rare, but it is possible when there is insufficient insulin in the body.

Symptoms of diabetes in dogs

Dogs with diabetes can have a combination of different clinical signs. Increased thirst, increased urination, and increased appetite are the most common symptoms. When cells become starved of glucose, the body may start to break down fat and muscles for energy, resulting in weight loss.

Diabetic dogs may also appear lethargic at times because their body isn’t getting enough energy. The glucose that is normally picked up by cells for energy will remain in the blood stream and won’t make it to the tissues that need it. This can also lead to problems with important internal organs like the liver and the brain. Vomiting and diarrhea can occur, especially if there are illnesses secondary to the diabetes like pancreatitis. Cataract formation in the eyes can also occur.  

Signs that can indicate the onset of a diabetic coma

If your diabetic dog was only recently diagnosed, it can take a few weeks for the diabetes to be well-controlled with treatment. During this time, you will need to look for signs that your dog’s blood sugar is too low. This can happen if too much insulin has been given. These overdosed pups may appear very lethargic and minimally responsive.

With severely low sugars, dogs can develop tremors and seizures. This is why it is important to get your dog to the vet if you see this. If you are comfortable checking your dog’s blood sugar at home with a glucometer, you can check his blood when he’s lethargic. More vets are using continuous-monitoring systems like the FreeStyle Libre. The sensors last up to two weeks and can be scanned with a reader or with a special app on your phone. It can detect sugar levels without having to poke your pup with a needle to obtain a blood sample!

Alternatively, prolonged hyperglycemia (aka very high glucose levels) can lead to lethargy, fatigue, restlessness, and depression. It can also cause neurologic problems such as hind limb weakness and twitching. Seizures are possible when your dog is in a hyperosmolar hyperglycemic state. The occasional high sugar reading is okay, but persistent high readings are problematic and can lead to this state.

Causes of diabetic comas

Diabetic comas are possible when diabetes is poorly controlled. Some pets can develop insulin resistance, even if they’ve been taking a certain insulin type for a long period of time. Infections and inflammatory diseases like pancreatitis can decrease the effectiveness of insulin. If too much insulin is given, it can cause a sharp drop in the amount of glucose in the blood stream. When the brain is starved of its main energy source, it can lead to seizures and a coma.

Fat is one of the tissues that are broken down for energy when there isn’t enough glucose entering the body’s cells. When the body breaks down fat too quickly, the liver converts the fat into a type of fuel that leaves behind ketone bodies as waste products. These are very acidic, and when they build up in the blood stream, they can lead to dehydration and harm the internal organs.

In situations where there is some insulin in the body but not enough to get diabetes under control, dogs can develop non-ketotic hyperosmolar diabetes mellitus. This means that there are no ketones present but the conditions are still suboptimal for the body. In this particular situation, diabetic comas are more likely to occur.

Treating diabetic comas

In a situation where a dog’s consciousness is altered, it is important to check his blood glucose. If you can do this at home and the sugar is very low, most vets recommend applying Karo syrup or corn syrup to the dog’s gums. This can help bring up blood sugar, and it can buy you some time while driving to your vet’s office or an emergency hospital.

If a sugar value is very high but your dog is acting normal, you can all your vet and ask about the next steps. If the glucose is very high but your dog is lethargic or non-responsive, he needs to head to the hospital or an emergency room right away!

Dogs with poorly controlled diabetes and diabetic ketoacidosis are typically hospitalized for fluid therapy, supportive care, and sometimes antibiotics. If there are neurologic signs like tremors or seizures, your vet will intervene with anti-seizure medications. They may run other tests to look for an underlying cause of why the diabetes is poorly controlled. Intact female dogs are difficult to control, and so your vet may recommend spaying if the dog is diabetic.


Diabetes can be difficult to control, especially in its early stages. It is important to follow your vet’s directions when giving food and insulin. Avoiding treats and snacks can help with better control. If control cannot be achieved, the risk of diabetes ketoacidosis and non-ketotic hyperosmolar diabetes mellitus will increase. If your diabetic dog is ever lethargic or non-responsive, contact your veterinarian or an emergency clinic immediately!  

Dr. Erica Irish author of Diabetic Comas in Dogs