Diabetes mellitus, sometimes called DM or just diabetes, is not just something people can get. Unfortunately, our dogs and cats can become diabetic as well.
What Is Diabetes?
When your dog eats a meal, their gastrointestinal tract works to break down their food into compounds it can use within the body. Proteins get broken down into amino acids and carbohydrates and starches get broken down into sugars, such as glucose. Some glucose circulating within the plasma of your dog's blood is normal, but there is a narrow window of normal blood glucose levels.
Your dog needs to be able to both store glucose within cells and tissues and then take glucose out to be used for energy. Specialized cells within your dog's pancreas create and excrete a hormone called insulin, which has the main function to decrease blood glucose levels by transporting them into cells for storage. Insulin excretion is directly related to blood glucose levels, so when a dog's blood glucose levels rise, more insulin is excreted by the pancreas.
Diabetes results from a problem with the body’s secretion or use of insulin; an untreated diabetic will have high blood glucose levels. Just like in people, there are two primary types of diabetes in dogs. Type I diabetes, sometimes referred to as insulin-dependent diabetes, results when the specialized cells within the pancreas that create insulin are destroyed and, as a result, the body produces less insulin. Type II diabetes, sometimes referred to as non–insulin-dependent diabetes, results from a combination of lowered insulin production and decreased sensitivity of cells to the insulin that is produced. In veterinary medicine, Type I seems to be more common in dogs, while Type II seems to be more common in cats.
The problem with unregulated blood glucose levels can be numerous. Chronically high blood glucose levels can lead to chronic inflammation, which can lead to increased tissue damage, especially in the blood vessels. This can result in kidney damage, blindness, and weakness or numbness in the limbs that can then lead to injuries. Extensive damage to the blood vessels can also damage the heart, the brain, and even the gastrointestinal tract.
One of the complications of uncontrolled diabetes is a life-threatening scenario called diabetic ketoacidosis (DKA). If a diabetic, especially an uncontrolled diabetic, is subjected to stressors, such as an infection, inflammation, or heart disease, this can cause an excess of ketones. Ketones are alternative fuel sources that are created by the liver but a buildup of them can have detrimental effects your dog's organ function and pH balance. A dog in DKA will have all the classic symptoms of diabetes listed below but they will also be lethargic, and they may start to pant more or breathe more heavily as a way to compensate for the extra acids in their blood.
What are the Symptoms of Diabetes?
Diabetic dogs will have the same symptoms, whether the diabetes results from a lack of insulin or a resistance to it. They will have an increased thirst, which coincides with an increase in urination. Your dog's kidneys will work to try and filter the glucose out to then recirculate it back into the blood stream, but once a certain level of glucose in the blood is reached they just can't filter it out anymore. Once this happens, your dog's kidneys will begin dumping the excess glucose into their urine. Glucose is also called an osmotic diuretic, meaning it holds onto water. The more glucose that your dog's kidneys are dumping into their urine, the more water they are losing as well. This can lead to the increase in urination.
This increase in urination then leads to the increased thirst and increased drinking. Diabetic dogs can also begin to lose weight despite having a great or even increased appetite. Although a diabetic dog may have a good appetite and has more than enough glucose in their blood stream, because they can't store it they can't utilize the it for energy later. So a diabetic dog's body goes into catabolic metabolism. This is a type of metabolism in which a dog's body breaks down fat and muscle tissue for energy. This explains why a diabetic dog will lose weight and even muscle mass despite having a great appetite.
Causes of Diabetes
The true causes of diabetes are not yet well understood, but there are different factors that can predispose dogs to becoming diabetic. There can be genetic predispositions as well as infectious agents, toxins, and inflammatory changes, especially within the pancreas. There are also other endocrine diseases such as hypothyroidism and hyperadrenocorticism (Cushing's Disease) that can make a dog more prone to developing diabetes. Most diabetic dogs are diagnosed between 7 and 11 years of age, although they can be as young as 4 or 5. Some breeds are more likely to become diabetic. This includes terriers like the Yorkshire terrier, Tibetan terrier, Cairn terrier, and Fox terrier, Samoyeds, Siberian Huskies, Pugs, and Toy poodles. Female dogs, especially unspayed females, are twice as likely to develop diabetes as males dogs.
Treatment of Diabetes
Diabetes in dogs is not curable or generally reversible, but the symptoms can be managed. The treatment of choice for diabetes in dogs is long-acting insulin. There are prescription diets that can help management from a nutritional standpoint, but diabetes in dogs has no hope of being well controlled without the use of insulin. A newly diagnosed dog will be prescribed a standard, weight based dose of a long-acting insulin to be administered subcutaneously twice daily in association with meals. The term 'long-acting' means that, while it can take longer to lower blood glucose, the insulin stays in your dog's system for several hours. You don't have to check a blood glucose before each dose, like you may in people, but after your dog has been on this regimen for at least a week your veterinarian will want to check something called a glucose curve. This is where a dog is fed and given insulin as normal in the morning and evening but serial blood glucose levels are obtained throughout the day to trend the dog's response to the insulin. Their dosage of insulin may be adjusted based on their glucose readings on that curve. In years past, dogs would either need to stay at the vet for the day or come back multiple times in one day for multiple blood draws, but within the past few years a new monitoring system originally intended for use in people has been utilized in dogs. The Freestyle Libre system allows pet owners to monitor glucose readings at home with no needles and no test strips! It can be a good alternative for pets that have intense anxiety at the vet or if driving to and from the vet multiple times in one day is just not feasible.
If your dog is in DKA, they will need more aggressive therapies. This can include intravenous fluids to replenish their hydration status and electrolyte balance as well as more frequent blood glucose monitoring and insulin administration.
Preventing Diabetes in Dogs
Because don't quite understand what causes diabetes in dogs, there's no conclusive way to prevent it. There are things that can be done to make a dog less prone to getting it, though. Since insulin is excreted by the pancreas, preventing inflammation of the pancreas (pancreatitis) may help. Pancreatitis can be caused by the feeding of fatty or inflammatory foods, such as processed hot dogs, bacon, and ham. Obesity in people can increase the risk of insulin resistance and, although not proven to be a direct cause of diabetes in dogs, it can also put your dog at risk. Keeping your dog fit and trim may help prevent a diagnosis of diabetes. If you aren't planning on breeding your female dog, have her spayed to lower her risk of developing diabetes later in life.
If your dog has another endocrine condition, such as hypothyroidism or Cushing's disease, ensure to keep all their follow up appointments with your vet to make sure those diseases are well controlled as this may help prevent diabetes.
Diabetes in dogs can be a scary diagnosis. Managing it can require diligence on your part. Dogs that become well controlled with their diagnosis, though, can live several years past their initial diagnosis. If you have concerns or questions about your dog's risk for diabetes, speak to your veterinarian.
Diabetic ketoacidosis in dogs. VCA Animal Hosptials.
Diabetes in pets. American Veterinary Medical Association.
Diabetes in pets. American Veterinary Medical Association.
Paul Pion DVM, Spadafori G. Veterinary partner. VIN.com. Published online August 8, 2017.