Hypoglycemia in Dogs: A Comprehensive Guide

What is Hypoglycemia?

Hypoglycemia is a medical condition where the blood sugar levels of an animal is outside the normal range. In dogs, normal levels of blood glucose fall within the range of 80-120 mg/dl. As such, hypoglycemic conditions are defined as any value under 80 mg/dl. Below this point, it becomes increasingly difficult for cells to perform the most basic, and often critical, functions. Severe symptoms, such as canine seizures, occur when glucose levels are reduced by more than half of the normal minimum. Any glucose level past 40 mg/dl is considered fatal.

Unlike a dog’s limited range of body temperature (101-102.5°F), glucose levels can fluctuate by up to 40 units throughout the day and still be considered normal. This is because dogs are constantly depleting or building glucose levels through intermittent spikes of physical exertion and food intake, followed by rest and regeneration. For instance, glucose levels are at a low when a dog is nearing the end of his sleep cycle, due to a prolonged period of inactivity. Conversely, glucose levels are at a high after a dog eats a meal or exercises. In healthy dogs, these fluctuations are not only normal, but temporary. This is because the body is constantly working to achieve chemical balance. In hypoglycemic states, however, the body struggles to increase glucose production to a normal, stable level, as there is not enough sugar or energy available to do so efficiently and effectively. Outwardly, this presents itself as overt canine lethargy.

Hypoglycemia can be thought of in two ways – primary and secondary. In primary cases, external factors cause hypoglycemia. In secondary cases, an underlying medical condition is the cause of hypoglycemia, a very serious side effect.

What Causes Primary Hypoglycemia in Dogs?

Hypoglycemia, in its primary form, is caused by a myriad of external factors.

  • Cold Weather: In cases of cold environments or drastic temperature changes, puppies are the most vulnerable. This makes sense given that internal organs are not fully developed, and therefore, less able to maintain self-regulation.
  • Extreme Exertion: More commonly associated with hunting dogs and high-performing sports dogs, extreme physical exertion can induce a state of incoordination, dizziness, or even unconsciousness. Here, the dog’s glucose reserves are depleted to a level that falls below the minimum range. The liver may be unable to independently produce glucose.
  • Extreme Dieting: The most common example of this is seen in overweight dogs. Rather than decreasing calorie intake or regulating meals, owners may opt for more drastic measures, that unfortunately, have the opposite effect. This quick weight loss tactic can negatively impact a dog’s ability to properly produce glucose. Fasting followed by intense physical exercise is an unhealthy and dangerous approach.
  • Insulin Intake: Generally, diabetic dogs are given insulin in order to reduce blood sugar levels. When treating diabetes, insulin dosing must be closely monitored, and reduced, as the dog loses weight. Failure to do so can result in an insulin surplus, causing the body to absorb too much glucose from the blood. At the same time, the liver will worsen the issue by releasing less glucose to the blood. Together, this results in fatally low levels of blood sugar.
  • Scarce Nutrition: Although all dogs are susceptible to hypoglycemia as a result of canine malnutrition, puppies are the most susceptible. This is attributed to underdeveloped teeth, smaller body fat stores, and weaker immune systems. It is most commonly diagnosed in cases of inadequate nutrition or starvation.

What Causes Secondary Hypoglycemia in Dogs?

In this situation, the dog is suffering from a more serious, primary medical condition, in which hypoglycemia is the secondary side effect. It is important to not only check for hypoglycemia, but dually, run additional tests that may be necessary to rule out associated medical conditions.

Internal Issues

  • Addison’s Disease: This disorder is caused when the adrenal glands fail to produce a sufficient number of associated hormones, which generally help to facilitate the transport of glucose into cells. In order to have the necessary power to initiate critical functions, cells require glucose-based energy.  
  • Diabetes Mellitus: This is the most common underlying health condition associated with hypoglycemia. Diabetes is the result of the liver and pancreas not being able to use or produce enough insulin. Consequently, blood sugar levels rise. When a diabetic dog is given excessive insulin, blood sugar levels quickly change from one extreme to another. For this reason, dogs with diabetes are more prone to hypoglycemia.
  • Insulinoma: This is a condition that causes tumors in the pancreas to secrete insulin, leading to an excess amount of insulin that cannot be used. Subsequently, glucose levels drop to a value defined as hypoglycemia.
  • Intestinal Parasites: Dogs may inadvertently consume parasite eggs or spores upon ingestion of infected soil, water, feces, or food. Parasites primarily feed off of sugar in the form of carbohydrates, such as glucose. Subsequently, this leads to decreased levels of blood sugar, and if too low, hypoglycemia.
  • Liver Disease: The liver is the organ responsible for regulating blood glucose through production, storage, and release. Naturally, it cannot do any part of its job as well while battling acute infection, resulting in lower overall levels of glucose.
  • Portosystemic Liver Shunts: This genetic condition causes a deformation of the liver. Similar to liver disease, a distorted liver cannot do its job as well as a healthy, normal-functioning liver. As a result, lower levels of glucose are manufactured, stored, and dispersed.
  • Sepsis: This is a widespread inflammatory response to an infection, which can result in a hyper or hypo reaction. In a hypo, or deficient response, not enough glucose is produced, triggering symptoms of hypoglycemia.

Signs & Symptoms of Canine Hypoglycemia

Hypoglycemia in dogs symptoms can range from mild to severe.


  • Appetite Loss: This is easiest to detect if feeding your dog measured amounts of food at regular, timed intervals. In more advanced cases, a dog may not have an appetite for normally craved foods, such as a treat or slice of turkey.
  • Lethargy: Be on the lookout for signs of canine weakness or extreme exhaustion. Although this seems simple, signs of hypoglycemia-induced lethargy can be difficult to spot due to a number of environmental variables, such as colder weather. Behaviorally, be aware of a decreased desire or ability to play. Try to monitor whether your dog is showing signs of excess fatigue from actions as simple as running, walking, or jumping on the couch. Excessive napping is also a potential indicator.
  • Muscle Twitches: Muscle