HBA1c

Reference Ranges for HbA1c

• Normal: < 42 mmol/mol
• Non-diabetic hyperglycaemia: 42-47 mmol/mol
• Diabetes diagnostic: ≥ 48 mmol/mol (confirm on a second sample if asymptomatic)
• Good diabetic control: target often around 48-53 mmol/mol (individualised)

Primary Care Approach

Step 1: Interpreting the Result

• Check if HbA1c is being used for diagnosis or monitoring
• Consider factors that can make HbA1c unreliable: anaemia, haemoglobinopathies, recent blood loss or transfusion, advanced kidney disease, pregnancy
• Always assess in clinical context: weight, symptoms (e.g. thirst, polyuria), medications (e.g. steroids)

Step 2: Non-diabetic Hyperglycaemia (42-47 mmol/mol)

• Offer lifestyle advice: diet, physical activity, weight loss support, smoking cessation
• Consider metformin if high risk (e.g. BMI ≥ 35, strong family history, high-risk ethnicity, worsening HbA1c)
• Repeat HbA1c in 6-12 months (earlier e.g. 3-6 months if close to 48 mmol/mol or symptoms develop)

Step 3: Diabetes Diagnosis (≥ 48 mmol/mol)

• If HbA1c ≥ 48 mmol/mol and patient symptomatic (polyuria, polydipsia, weight loss) → diagnosis can be made from a single sample and treatment can be started immediately
• If HbA1c ≥ 48 mmol/mol and patient asymptomatic → repeat HbA1c to confirm diagnosis
• Second sample should be repeated as soon as practical (usually within 2 weeks)
• If second HbA1c is also ≥ 48 mmol/mol → confirm diagnosis of diabetes
• If second HbA1c is < 48 mmol/mol → consider pre-diabetes or repeat testing depending on clinical context
• If HbA1c may be unreliable (e.g. anaemia, haemoglobinopathy) → use fasting plasma glucose or oral glucose tolerance Test (OGTT)
• Once diagnosis confirmed (or symptomatic diagnosis made):
  • Arrange foot check
  • Refer for retinal screening
  • Check BP and lipids
  • Screen for CKD (U&E and urine ACR)
  • Discuss lifestyle changes and try medication if appropriate

Step 4: Monitoring in Known Diabetes

• Check HbA1c every 3-6 months if adjusting treatment or if not at target
• Check HbA1c about every 6 months if stable and at/near target
• Assess trends: rising levels may indicate adherence issues, intercurrent illness, steroid use, or need to escalate treatment

Example: Type 2 Diabetes Escalation Pathway in Primary Care (Before Secondary Care Referral)

• Step 1: Try metformin (if tolerated and egfr appropriate), titrated gradually to maximum tolerated dose (up to 1g twice daily)
• Step 2: If HbA1c above target (usually > 53 mmol/mol), add second agent based on comorbidities (e.g. sglt2 inhibitor if CVD/CKD/HF risk, or dpp4 inhibitor (gliptin) / sulfonylurea if appropriate)
• Step 3: If still above target, move to triple therapy (e.g. metformin + sglt2 inhibitor + dpp4 inhibitor or sulfonylurea)
• Step 4: Consider glp-1 receptor agonist if BMI ≥ 35 with specific psychological or medical problems associated with obesity, or if insulin would have significant occupational implications
• Step 5: If HbA1c remains markedly elevated (e.g. persistently > 69-75 mmol/mol despite optimised triple therapy) consider insulin initiation in primary care if within local pathway, or refer to secondary care for insulin assessment and structured education

When to Refer to Secondary Care

• HbA1c > 86 mmol/mol (or symptomatic hyperglycaemia) despite escalation in primary care
• Recurrent hypoglycaemia or uncertainty about diagnosis
• Type 1 diabetes, suspicion of type 1 diabetes, or ketosis
• Need for complex insulin regimens or pump therapy
• Complications requiring specialist input (e.g. progressive nephropathy, sight-threatening retinopathy)

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