Low blood sugar (hypoglycaemia)

Definition
Hypoglycaemia is a clinical condition characterized by abnormally low plasma glucose concentration, typically defined as blood glucose levels below 4.0 mmol/L (72 mg/dL) in diabetic patients and below 3.0 mmol/L (54 mg/dL) in non-diabetic individuals, accompanied by autonomic and/or neuroglycopenic symptoms.

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Causes

1. In People with Diabetes

• Excessive insulin administration.

• Sulfonylurea overdose (e.g., glibenclamide, gliclazide, glimepiride).

• Skipping or delaying meals after taking insulin or oral hypoglycaemic drugs.

• Increased physical activity without adequate carbohydrate intake.

• Alcohol consumption without food intake.

2. In People without Diabetes

• Severe liver disease (impaired gluconeogenesis).

• Sepsis.

• Hormonal deficiencies (e.g., adrenal insufficiency, hypopituitarism).

• Insulinoma (rare pancreatic β-cell tumor).

• Critical illness or prolonged fasting.

• Post–bariatric surgery hypoglycaemia.

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Pathophysiology

Glucose homeostasis is maintained through a balance between insulin secretion, counter-regulatory hormones (glucagon, adrenaline, cortisol, growth hormone), and hepatic glucose production. Hypoglycaemia occurs when:

• Glucose utilization exceeds supply.

• Hepatic glucose output is insufficient.

• Insulin or insulin-like activity is excessive.

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Clinical Features

Autonomic Symptoms (adrenergic activation)

• Sweating.

• Palpitations.

• Tremor.

• Anxiety.

• Hunger.

Neuroglycopenic Symptoms (glucose deprivation to the brain)

• Confusion.

• Drowsiness.

• Slurred speech.

• Visual disturbances.

• Seizures.

• Loss of consciousness.

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Diagnosis

Whipple’s Triad

1. Symptoms consistent with hypoglycaemia.

2. Low plasma glucose concentration.

3. Resolution of symptoms after raising blood glucose.

Investigations

• Capillary or plasma glucose measurement during symptoms.

• Serum insulin, C-peptide, proinsulin (if endogenous hyperinsulinism suspected).

• β-hydroxybutyrate (low in insulin-mediated hypoglycaemia).

• Cortisol and thyroid function tests if endocrine cause suspected.

• Imaging for insulinoma (CT, MRI, endoscopic ultrasound).

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Management

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Immediate Treatment

If the patient is conscious and able to swallow

• Give 15–20 g of fast-acting carbohydrate:

  • Glucose tablets.

  • Glucose gel.

  • Sugary drinks (non-diet).

• Recheck blood glucose in 10–15 minutes; repeat if still low.

• Follow with long-acting carbohydrate (e.g., bread, biscuits) once recovered.

If the patient is unconscious or unable to swallow

• Glucagon 1 mg IM/SC (adults and children >25 kg; 0.5 mg for smaller children).

• Glucose 10% IV, 100–200 mL over 10 minutes, or glucose 50% IV, 25–50 mL slowly (hospital setting).

• Monitor closely and treat underlying cause.

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Long-Term Management

1. For People with Diabetes

• Adjust insulin regimen or oral hypoglycaemic dose.

• Educate on timing of meals, carbohydrate counting, and hypoglycaemia recognition.

• Avoid skipping meals.

• Reduce alcohol consumption and always consume with food.

• Continuous glucose monitoring (CGM) for those with recurrent hypoglycaemia.

2. For Non-Diabetic Hypoglycaemia

• Treat underlying cause (e.g., surgery for insulinoma).

• Small frequent meals, complex carbohydrates, and avoidance of high-sugar foods in reactive hypoglycaemia.

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Pharmacological Details – Key Medications

Glucagon

• Generic name: glucagon.

• Dose (adults): 1 mg IM/SC; repeat if necessary after 15 minutes if IV glucose unavailable.

• Dose (children): <25 kg or <8 years, 0.5 mg IM/SC.

• Used for emergency treatment of severe hypoglycaemia when IV access is not available.

Glucose (Dextrose)

• Generic name: glucose monohydrate (dextrose).

• IV dosing:

  • 10% glucose: 100–200 mL IV over 10 minutes.

  • 50% glucose: 25–50 mL slow IV bolus, followed by infusion if needed.

Octreotide (for sulfonylurea-induced hypoglycaemia)

• Generic name: octreotide acetate.

• Dose: 50–100 mcg SC every 6–12 hours or continuous IV infusion 50–125 mcg/hour.

• Inhibits insulin secretion and prevents recurrent hypoglycaemia.

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Complications

• Seizures and coma.

• Cardiac arrhythmias.

• Neurological damage with prolonged severe hypoglycaemia.

• Hypoglycaemia unawareness (loss of warning symptoms).

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Prevention Strategies

• Individualized glycaemic targets for diabetic patients at risk of hypoglycaemia.

• Regular review of insulin therapy and oral hypoglycaemics.

• Patient education on recognition and early management of symptoms.

• CGM or flash glucose monitoring for high-risk individuals.