Hypoglycemia in Rabbits: Does It Occur, and Should Glucose Be Administered?

Hypoglycemia in Rabbits: Does It Occur, and Should Glucose Be Administered?
Questions regarding low blood glucose (hypoglycemia) frequently arise in clinical practice, often leading to inappropriate management. Many veterinarians become anxious when encountering low glucose readings and rush to administer oral glucose to prevent adverse effects. But is this the correct approach? To evaluate whether hypoglycemia is a pathology requiring intervention—and how to treat it without relying on oral glucose—we must first understand normal blood values and the unique physiology of these animals. Methods used for dogs and cats cannot always be applied to rabbits and other herbivores.

Understanding Blood Glucose in Herbivores
Reported normal blood glucose ranges for rabbits are quite broad, typically between 4.2 to 8.2 mmol/L (Gillett 1994, Campbell 2004, Jenkins 2006). In contrast, dogs have a narrower range of 3.3 to 6.2 mmol/L. This difference is believed to stem from the herbivore’s continuous cycle of glucose synthesis, storage, breakdown, and utilization, supplemented by volatile fatty acids (VFAs) derived from plant fermentation. For comparison, cows range from 1.89 to 6.05 mmol/L and horses from 4.4 to 9 mmol/L.

In healthy herbivores, fluctuations in blood glucose are rarely a cause for concern. These animals primarily utilize free fatty acids as their main energy source. Stress-induced cortisol release can trigger gluconeogenesis, where glucose is rapidly produced and then broken down into pyruvate and lactate. While lactate levels may rise temporarily, it is usually short-lived. Furthermore, high-fiber diets have been shown to naturally lower blood glucose.

Hyperglycemia vs. Hypoglycemia
In a study of 907 rabbits by Harcourt-Brown & Harcourt-Brown (2012), not a single case of diabetes mellitus was found. However, severe hyperglycemia (> 20 mmol/L) was observed and is considered dangerous. High glucose levels are often linked to intestinal obstruction; it is believed that during periods of anorexia, the body mobilizes fat and glycogen stores from the liver, causing an initial spike in glucose followed by a rapid drop. In such cases, clinicians should be more concerned about ketosis than the glucose reading itself. The same study noted that true hypoglycemia is also typically induced by anorexia.

Clinical Management: Why Oral Glucose is Not the Answer
I frequently emphasize to veterinarians and students that hypoglycemia in rabbits is usually "anorexia-induced hypoglycemia." The primary treatment should focus on the underlying cause rather than simply feeding sugar. Management involves monitoring symptoms, treating the root pathology, and providing appropriate recovery diets designed for herbivores.

True hypoglycemia is rare in herbivores, occurring in only about 1.76% of cases, usually due to starvation or a lack of fermentation. This is closely tied to gastrointestinal (GI) disorders such as GI stasis and obstructions, which cause pain and anorexia in 100% of cases (Butsurin, 2014). Other rare causes include:

Insulinoma: Extremely rare (only 1 out of 16 hypoglycemic cases in the 2012 study), presenting with weakness, ataxia, and seizures (Foxx et al., 2022).
Hepatic Lipidosis: Fatty liver changes can lead to hypoglycemia once glycogen stores are exhausted due to stress or adrenaline.
The Dangers of Oral Sugar
While oral glucose is a standard emergency fix for other species, it should be avoided in rabbits for several reasons:

Alternative Energy: Rabbits quickly switch to using fatty acids or recycling lactate via the Cori cycle (converting lactate to pyruvate for gluconeogenesis).
Addressing the Cause: Once pain is managed and assisted feeding with recovery diets begins, the glucose levels usually stabilize. If urgent glucose is required, intravenous (IV) administration is preferred.
Microbial Imbalance: Feeding glucose (including fruit, juice, or honey) can trigger the rapid overgrowth of lactic acid bacteria in a stagnant gut. This shifts the pH, leading to enteritis and severe dysbiosis (microbial imbalance).

Brief Insights: The Strepsirrhines (Slow Lorises and Bushbabies)
Slow lorises and bushbabies share many similarities with lemurs as they all belong to the suborder Strepsirrhini (prosimians), though they diverge at the infraorder level.

The term Strepsirrhini means "wet-nosed," distinguishing them from the Haplorhini ("dry-nosed"), which includes monkeys and apes. Formerly known as "prosimians" or "pre-monkeys," they are often considered more evolutionarily primitive than simians. Key characteristics include:

Small Stature: Generally much smaller than monkeys or apes.
Grooming Claw: While most digits have flat nails and pads like monkeys, the second toe has a sharp claw used for grooming.
Opposable Thumbs: Separated from the palm to aid in gripping.
Dental Comb: The lower incisors and canines form a comb-like structure used for grooming and scraping tree bark to feed on sap and gum.
Protruding Snout: They have a keen sense of smell, a large olfactory lobe, and a highly functional vomeronasal organ for detecting pheromones.
Nocturnal Vision: Large, forward-facing eyes equipped with a Tapetum lucidum—a reflective layer behind the retina that enhances night vision.
Smaller Brain: Relative to body size, their brains are smaller than those of simians.
Brush-like Tail: Usually long and bushy.
Agility: Excellent at climbing and leaping.
Vitamin C Synthesis: Unlike monkeys, apes, and humans—who must ingest Vitamin C—this group can synthesize their own.
Despite these unique traits, their diet remains diverse (omnivorous), consisting of plants, sap, nectar, fruits, leaves, insects, and small animals, much like other primates.