Type 1 diabetes

Quick Overview

Type 1 diabetes (T1DM) results from autoimmune destruction of pancreatic β-cells, causing absolute insulin deficiency. Typically presents in childhood/adolescence but can occur at any age. Requires lifelong insulin replacement with structured carbohydrate counting and sick day management to prevent acute complications (DKA, hypoglycaemia) and achieve glycaemic targets.

Core Facts & Concepts

Diagnostic Criteria

• Random glucose ≥11.1 mmol/L with symptoms OR fasting glucose ≥7.0 mmol/L OR HbA1c ≥48 mmol/mol (6.5%)
• Autoantibodies: GAD, IA-2, ZnT8 (positive in 85-90% at diagnosis)
• C-peptide: Low/undetectable (<200 pmol/L) confirms insulin deficiency

HbA1c Targets (NICE NG17)

• Adults: ≤48 mmol/mol (6.5%) if achievable without problematic hypoglycaemia
• Consider ≤53 mmol/mol (7.0%) if hypoglycaemia risk or reduced awareness
• Children/young people: <48 mmol/mol target

Insulin Regimens

• Basal-bolus (multiple daily injections): Long-acting (glargine/detemir) + rapid-acting (aspart/lispro) with meals
• Continuous subcutaneous insulin infusion (CSII/pump): NICE NG17 recommends if HbA1c ≥69 mmol/mol (8.5%) despite optimised MDI OR disabling hypoglycaemia

Carbohydrate Counting

• 10g carbohydrate = 1 portion
• Insulin:carbohydrate ratio typically 1 unit:10-15g (individualised)
• Structured education programmes: DAFNE (adults), BERTIE

Problem-Solving Approach

Sick Day Rules (🚩 Critical)

1. Never stop insulin - increase by 10-20% if unwell
2. Monitor glucose 4-hourly minimum
3. Check blood/urine ketones if glucose >15 mmol/L
4. Maintain hydration (200ml fluid/hour)
5. Take easily absorbed carbohydrate if unable to eat normally
6. Seek urgent help if: ketones ≥3.0 mmol/L, persistent vomiting, drowsiness

Hypoglycaemia Management

• Mild (glucose <4.0 mmol/L, alert): 15-20g fast-acting carbohydrate (4-5 glucose tablets, 150ml juice)
• Severe (unconscious/fitting): 1mg IM glucagon OR 150-200ml 10% glucose IV
• Recheck at 15 minutes; if still <4.0 mmol/L, repeat treatment
• Follow with long-acting carbohydrate once >4.0 mmol/L

⚠️ Warning: Impaired awareness of hypoglycaemia develops in 20-25% - avoid glucose <4.0 mmol/L strictly for 6 weeks to restore awareness

Analysis Framework

Visual Aid

Key Points Summary

✓ Diagnosis: Autoantibodies (GAD/IA-2/ZnT8) + low C-peptide (<200 pmol/L) confirm T1DM
✓ HbA1c target: ≤48 mmol/mol (6.5%) without problematic hypoglycaemia (NICE NG17)
✓ Insulin regimen: Basal-bolus standard; consider pump if HbA1c ≥69 mmol/mol despite MDI
✓ Hypoglycaemia: Treat <4.0 mmol/L with 15-20g fast-acting carbohydrate; severe = 1mg IM glucagon
✓ Sick day rules: Never stop insulin, increase by 10-20%, check ketones if glucose >15 mmol/L
✓ Carbohydrate counting: 1 unit rapid-acting per 10-15g carbohydrate (individualised ratio)
✓ Red flags: Ketones ≥3.0 mmol/L, persistent vomiting, drowsiness - urgent medical review required

📌 Remember: SICK - Stop never (insulin), Increase dose 10-20%, Check ketones 4-hourly, Keep hydrated