What are the steps to diagnose and manage hypoglycaemia (low blood sugar)?

Hypoglycemia Differential Diagnosis and Management

Immediate Diagnostic Approach

When hypoglycemia is suspected, confirm with immediate blood glucose measurement, but if testing is unavailable, treat first and confirm retrospectively. 1, 2

Key Diagnostic Thresholds

• Alert value: Blood glucose ≤70 mg/dL (3.9 mmol/L) - this triggers neuroendocrine responses and requires action regardless of symptom severity 3, 1
• Clinically significant: Blood glucose <54 mg/dL (3.0 mmol/L) - neuroglycopenic symptoms begin, requiring immediate treatment 3, 1
• Severe hypoglycemia: Altered mental/physical status requiring external assistance for recovery, with no specific glucose threshold 3, 1

Clinical Presentation to Document

Autonomic symptoms: Shakiness, sweating, tachycardia, palpitations, anxiety, tremor, hunger 1, 2, 4

Neuroglycopenic symptoms: Confusion, irritability, blurred vision, drowsiness, slurred speech, inability to concentrate, personality changes, seizures, unconsciousness 4, 5

Differential Diagnosis Framework

In Diabetic Patients (Most Common)

Medication-related causes (prioritize these first):

• Insulin: Excessive dosing, timing mismatch with meals, or dose not adjusted for activity 3, 6
• Sulfonylureas/insulin secretagogues: Highest risk oral agents for hypoglycemia 3, 7
• Combination therapy: Insulin or secretagogues combined with other agents 3, 7

Precipitating factors to identify:

• Delayed or skipped meals 3, 2
• Increased physical activity without dose adjustment 3, 2
• Alcohol consumption (especially without food) 3, 2
• Fasting for procedures 2
• Sleep (nocturnal hypoglycemia) 6, 7
• Declining renal function (reduced insulin clearance) 3

High-risk patient characteristics:

• Advanced age (>60 years) 3
• African American race 3
• History of hypoglycemia unawareness 3, 2
• Prior severe hypoglycemia episodes 3
• Type 1 diabetes with impaired counterregulatory responses 3, 6

In Non-Diabetic Patients

Consider these causes when diabetes medications are excluded:

• Critical illness or organ failure 5
• Insulinoma or other endocrine disorders 5
• Medication effects (non-diabetes drugs) 5
• Alcohol-induced hypoglycemia 5
• Post-gastric surgery (dumping syndrome) 5
• Sepsis or severe infection 5

Immediate Management Protocol

For Conscious Patients

Administer 15-20g oral glucose (preferred) or any glucose-containing carbohydrate 1, 2

• Recheck blood glucose after 15 minutes 1, 2
• If hypoglycemia persists (<70 mg/dL), repeat treatment 1, 2
• Once normalized (>70 mg/dL), provide starchy or protein-rich food if next meal is >1 hour away 1

Critical caveat: For patients on α-glucosidase inhibitors, use only monosaccharides (glucose tablets) as the drug blocks polysaccharide digestion 3

For Unconscious or Severely Impaired Patients

Administer glucagon 0.5-1.0 mg IM or 20-40 mL of 50% glucose solution IV 1, 4, 8

• Dosing: Adults receive 1 mg; children <44 lbs (20 kg) receive 0.5 mg 4
• Turn patient on side to prevent aspiration if vomiting occurs 4
• Call emergency services immediately 4
• If no response within 15 minutes, give second glucagon dose and notify emergency services 4
• Once awake and able to swallow, provide fast-acting sugar (juice) followed by long-acting carbohydrate (crackers, sandwich) 4

All patients at risk for severe hypoglycemia should have glucagon prescribed, with caregivers trained in administration 2, 4

Post-Event Investigation and Prevention

Mandatory Reassessment Triggers

Any episode of level 2 hypoglycemia (<54 mg/dL) or level 3 (severe) hypoglycemia requires immediate reevaluation of the treatment regimen 3, 2

For Hypoglycemia Unawareness

Raise glycemic targets strictly for at least several weeks to partially reverse unawareness and reduce future risk 3, 1, 2

• This is a Grade A recommendation from the American Diabetes Association 3
• Avoid hypoglycemia completely during this period 3

Medication Adjustments

Insulin-treated patients: Review and reduce doses, especially if hypoglycemia occurred with physical activity within 1-2 hours of injection 3

Sulfonylurea patients: Consider switching to agents with lower hypoglycemia risk (DPP-4 inhibitors, GLP-1 agonists, SGLT2 inhibitors) 3, 7

Metformin patients: Can continue with dose reduction if GFR 30-45 mL/min 3

Monitoring Strategies

Implement continuous glucose monitoring (CGM) for high-risk patients: Those with hypoglycemia unawareness, frequent nocturnal hypoglycemia, or history of severe episodes 7

• CGM with automated low glucose suspend reduces hypoglycemia in type 1 diabetes 3
• Real-time CGM particularly benefits those with impaired awareness 7

Common Pitfalls to Avoid

Never delay treatment waiting for glucose confirmation - treat suspected hypoglycemia immediately if testing unavailable 1, 2

Never use sliding scale insulin as sole regimen - strongly discouraged by the American Diabetes Association 2

Never aggressively pursue near-normal A1C in patients with recurrent hypoglycemia - severe or frequent hypoglycemia is an absolute indication for treatment modification 3

Never fail to coordinate meal timing with medication administration - particularly critical for insulin secretagogues and premixed insulin regimens 3

Never overlook alcohol consumption - advise patients to consume alcohol only with food to reduce hypoglycemia risk 3, 2

Institutional/Hospital Settings

Implement standardized hypoglycemia treatment protocols 1, 2

• Train all staff in recognition and treatment 3, 2
• Ensure immediate access to glucose tablets or equivalent 3, 2
• Notify physician for all glucose values <50 mg/dL or >350 mg/dL 3, 2
• Have glucagon available for IM injection without requiring patient transport 3
• Consider housing high-risk patients closer to medical units 3