The brain has virtually no glucose storage capacity and depends entirely on continuous blood glucose supply. When blood glucose drops below 40-60 mg/dL, neuronal function deteriorates rapidly, progressing from weakness to seizures to coma. A properly prepared dextrose bolus can reverse life-threatening neuroglycopenia within 1-2 minutes. Use the Dextrose Calculator to ensure accurate bolus and CRI preparation, and the Drug Formulary for concentration references.
Identifying the underlying cause of hypoglycemia is essential for long-term management after the acute emergency is resolved.
Insulinoma: Insulin-secreting pancreatic beta cell tumors are the most common cause of persistent hypoglycemia in middle-aged to older dogs. Diagnosis requires demonstrating inappropriately elevated insulin levels during a hypoglycemic episode (insulin:glucose ratio).
Sepsis: Severe sepsis causes hypoglycemia through increased peripheral glucose utilization by inflammatory cells, impaired hepatic gluconeogenesis, and cytokine-mediated insulin resistance paradoxically combined with enhanced glucose uptake.
Hepatic failure: The liver is the primary site of gluconeogenesis and glycogen storage. Severe hepatic dysfunction (portosystemic shunts in puppies, acute liver failure, end-stage cirrhosis) impairs glucose homeostasis.
Neonatal and toy breed hypoglycemia: Neonates and toy breed puppies have limited glycogen reserves, high metabolic rates, and immature gluconeogenic enzymes. Hypoglycemia can develop within hours of missed meals.
Xylitol toxicity: Xylitol causes massive insulin release in dogs, leading to profound hypoglycemia within 30-60 minutes of ingestion. Doses as low as 0.1 g/kg can cause hypoglycemia.
Iatrogenic insulin overdose: Accidental or intentional administration of excessive insulin in diabetic patients. Common with owner dosing errors or during DKA management.
Hypoglycemia clinical signs correlate with the blood glucose level and the rate of decline:
Mild (50-60 mg/dL): Lethargy, weakness, trembling, increased appetite (polyphagia). These early signs are often intermittent and may be missed by owners.
Moderate (30-50 mg/dL): Ataxia, disorientation, muscle fasciculations, visual disturbances, behavioral changes (aggression or anxiety).
Severe (<30 mg/dL): Seizures, opisthotonus, coma, and death. Prolonged severe hypoglycemia causes irreversible neuronal necrosis, particularly in the cerebral cortex, hippocampus, and caudate nucleus.
Warning: Chronic insulinoma patients may tolerate remarkably low glucose levels (20-30 mg/dL) without obvious signs due to cerebral adaptation. Conversely, patients with acute-onset hypoglycemia (xylitol, insulin overdose) may seize at 40-50 mg/dL. The rate of glucose decline is as important as the absolute level.
The emergency treatment for symptomatic hypoglycemia is an IV dextrose bolus:
Step 1: Draw up 50% dextrose at a dose of 0.5-1.0 mL/kg.
Step 2: Dilute 1:2 to 1:4 with sterile saline or sterile water to reduce osmolarity. Undiluted 50% dextrose (2,525 mOsm/L) is extremely hyperosmolar and can cause phlebitis, thrombophlebitis, and perivascular tissue necrosis if extravasation occurs.
Step 3: Administer slowly IV over 2-5 minutes. Rapid bolus administration can cause a transient hyperglycemia that triggers excessive insulin release, resulting in rebound hypoglycemia.
Step 4: Recheck blood glucose within 5-10 minutes. If still hypoglycemic, repeat the bolus at 50% of the initial dose.
Step 5: Once glucose is above 80 mg/dL, transition immediately to a dextrose CRI to prevent recurrence.
If IV access is not available, 50% dextrose can be applied to the buccal mucosa (sugar water on the gums) for transmucosal absorption. This is less effective than IV administration but can be life-saving as a first-aid measure for owners at home. Dose: 1-2 mL of 50% dextrose or corn syrup rubbed on the gums.
After the initial bolus, a continuous rate infusion of dextrose maintains blood glucose stability. The target CRI concentration is typically 2.5-5% dextrose added to maintenance crystalloid fluids.
| Desired Concentration | Volume of 50% Dextrose to Add | Fluid Bag Size | Preparation Method |
|---|---|---|---|
| 2.5% dextrose | 50 mL | 1 liter bag | Remove 50 mL from bag, add 50 mL of 50% dextrose |
| 5% dextrose | 100 mL | 1 liter bag | Remove 100 mL from bag, add 100 mL of 50% dextrose |
| 2.5% dextrose | 25 mL | 500 mL bag | Remove 25 mL from bag, add 25 mL of 50% dextrose |
| 5% dextrose | 50 mL | 500 mL bag | Remove 50 mL from bag, add 50 mL of 50% dextrose |
The math: To make X% dextrose from 50% stock, the volume to add = (desired % ÷ 50%) × final volume. The Dextrose Calculator automates these calculations for any bag size and desired concentration.
After initiating dextrose CRI, monitor blood glucose every 1-2 hours for the first 6-8 hours, then every 4-6 hours once stable. Target blood glucose is 80-150 mg/dL. If glucose drops below 80 mg/dL, increase the dextrose concentration (e.g., from 2.5% to 5%). If glucose exceeds 200 mg/dL, decrease the concentration or switch to non-supplemented fluids.
For insulinoma patients, consider concurrent medical management with prednisone (0.5-1 mg/kg PO BID) to promote gluconeogenesis and frequent small meals. For xylitol toxicity, monitor liver enzymes at 24 and 72 hours post-ingestion, as hepatic necrosis can develop even after glucose stabilization.
- Hypoglycemia is a neurologic emergency; the brain depends entirely on continuous glucose supply with no significant storage capacity.
- Dextrose 50% bolus at 0.5-1 mL/kg IV diluted 1:2-1:4, given slowly over 2-5 minutes, is the emergency treatment.
- Always dilute 50% dextrose before IV administration to prevent phlebitis and tissue necrosis.
- Transition immediately to a dextrose CRI (2.5-5%) after the initial bolus to prevent rebound hypoglycemia.
- Monitor blood glucose every 1-2 hours initially; adjust CRI concentration based on response.
- Identify the underlying cause (insulinoma, sepsis, hepatic failure, xylitol, insulin overdose) for definitive management.