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Hypoglycemia in dogs: A vet's guide

Sick Bulldog on table at vet
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Hypoglycemia is a condition characterized by low blood sugar. Although not considered a disease itself, it can be an indication of an underlying health issue. It is commonly seen in diabetic dogs, but it can occur with a wide range of disease processes. Read on to learn more about hypoglycemia and what to do if your dog shows any signs of it.

What is hypoglycemia in dogs?

“Hypoglycemia” means that there are low levels of glucose in the blood. Glucose is required for life, as it is the predominant energy source used by the brain. The brain has a high and continuous requirement for glucose, and it cannot create or store glucose, so hypoglycemia causes many neurological symptoms and can be life-threatening if left untreated.

In healthy animals, blood glucose levels are kept within a normal range by the actions of the glucose-lowering hormone insulin and glucose-elevating hormones such as glucagon, cortisol, epinephrine, norepinephrine, and growth hormone. Hypoglycemia can result when there is insufficient dietary glucose, an increased demand for glucose, dysfunction of glucose-producing pathways in the liver, or abnormal levels of glucose-regulating hormones.

Symptoms of hypoglycemia in dogs

Although hypoglycemia can have effects throughout the entire body, most symptoms are neurological in nature because of the brain’s sensitivity to low glucose levels. Symptoms commonly seen in hypoglycemia include:

  • Anxiety or change in behavior
  • Inappetence
  • Muscle tremors
  • Incoordination
  • Weakness
  • Lethargy
  • Collapse
  • Convulsions or seizures
  • Coma
  • Death in severe cases

These symptoms vary depending on the severity of hypoglycemia and how quickly it comes about. If you suspect that your dog is hypoglycemic, you should rub a sugary substance such as honey on their gums and take them straight to the vet.

What causes hypoglycemia in dogs?

Dog at vet

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There are numerous causes of hypoglycemia in dogs, including but not limited to:

  • Insulin overdose: Hypoglycemia is the most serious side effect of insulin treatment in dogs with diabetes mellitus, as well as the most common complication. It occurs when too much insulin is given to a diabetic dog or when they eat too little or exercise too much, subsequently lowering blood glucose levels.
  • Insulinoma: Insulinomas are functional tumors of the beta cells of the pancreas, which secrete insulin. These tumors secrete excessive amounts of insulin, resulting in hypoglycemia. The resulting high insulin levels also inhibit glucose-producing pathways, further contributing to low blood sugar. Insulinomas are more common in middle-aged, large-breed dogs.
  • Other cancers: Cancers in other areas of the body can also cause hypoglycemia due to tumors consuming glucose and sometimes stimulating the release of insulin or insulin analogs. The most common tumors outside the pancreas associated with hypoglycemia are located in the liver and muscles.
  • Toxins: Several toxins have been reported to cause hypoglycemia in dogs, the most common being xylitol, a sugar substitute used in many sugar-free candies, chewing gums, and peanut butters. Other toxic causes include some human prescription medications, human non-steroidal anti-inflammatory drugs like ibuprofen, illicit drugs, pesticides, and plants.
  • Breed/size/age: Hunting dog hypoglycemia occurs because of their lean build and high energy requirements for work. Toy-breed dogs and young puppies are predisposed to hypoglycemia due to insufficient glycogen stores (a source of glucose) and limited fat and muscle mass to break down and convert into glucose. Additionally, neonatal puppies have immature livers, which may affect their ability to regulate blood glucose.
  • Liver disease: Severe liver diseases can result in decreased glucose production via reduced glycogen stores and decreased conversion of broken-down fats and proteins into glucose. Some liver diseases that can cause hypoglycemia include hepatitis, liver cancers, hepatic lipidosis (“fatty liver”), cirrhosis, and congenital portosystemic shunt.
  • Addison's disease: Addison’s disease is characterized by insufficient cortisol production by the adrenal glands. Because cortisol is a hormone that counteracts insulin and helps regulate blood glucose, a lack of cortisol can result in high levels of insulin in some Addisonian dogs.
  • Infection: Infections such as parvovirus, babesiosis, and sepsis can cause hypoglycemia due to excessive glucose consumption in these disease processes.

How is hypoglycemia diagnosed in dogs?

Hypoglycemia is diagnosed in dogs using a simple blood test to check the concentration of glucose in the blood. If it is under a certain level, the dog is considered hypoglycemic.

The veterinarian may wish to perform further diagnostic tests to determine the underlying cause of hypoglycemia, which include additional blood tests, urinalysis, and imaging.

It should be noted that human glucometers may underestimate canine blood glucose levels, resulting in readings consistent with hypoglycemia despite normal glucose levels. For this reason, only veterinary glucometers should be used to monitor diabetic dogs receiving insulin therapy.

How to treat hypoglycemia in dogs

Female veterinarian with a pup at the office

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Hypoglycemia can be life-threatening in dogs if left untreated, and it can cause permanent brain damage if treatment is delayed. It is imperative to seek immediate veterinary attention if a dog is showing signs of hypoglycemia to reestablish normal glucose levels.

In the case of a hypoglycemic episode, a sugary substance such as honey, syrup, or glucose solution can be rubbed onto oral mucous membranes like the gums, cheek, and tongue. If the dog is unconscious, care should be taken with liquids due to the risk of aspiration. Oral glucose is not as effective as intravenous glucose, however, so dogs should be taken directly to the vet for treatment and possible hospitalization.

Hypoglycemic dogs are generally given dextrose (a concentrated glucose solution) intravenously to increase blood glucose levels. They may also receive a steroid like prednisone to counteract insulin in the circulation. In cases that don’t respond to intravenous dextrose, glucagon infusions may be used.

What is the prognosis of hypoglycemia in dogs?

The prognosis of dogs with hypoglycemia depends on the underlying cause of low blood sugar. While some dogs have one-off cases that resolve quickly and don’t recur, others may have repeated episodes with more severe symptoms. In these cases, veterinarians can work with owners to investigate the reason for hypoglycemia, and complicated cases may require referral to a specialist to determine the underlying cause.

Dr. Diana Hasler graduated with distinction from the University of Edinburgh Royal (Dick) School of Veterinary Studies in 2018. She has experience working as a small animal veterinarian in general practice, where she has treated many dogs, cats, rabbits, and rodents. She has also recently branched out into the field of medical communications, doing freelance work as a medical editor and writer. Dr. Hasler currently lives in Edinburgh where she enjoys spending time with her husband Gavin and playing with their feisty tabby cat Poppy.