Screening for Diabetes Mellitus

Diabetes can be screened using an HbA1C level, fasting plasma glucose, or an Oral Glucose Tolerance Test (OGTT).

If fasting plasma glucose is used alone for screening, ≥ 2 abnormal readings are required to make the diagnosis. An HbA1C level should be obtained after making the diagnosis to establish the level of glycemic control over the past 3 months. The HbA1C will also be used to dictate therapy.

Diagnosis	HbA1C	Fasting glucose (mmol/L)	Glucose Tolerance (mmol/L)
No diabetes	< 5.7%	≤ 5.6	≤ 7.8
Pre-diabetes (IGR)	5.7 – 6.5	5.6 – 6.9 (IFG)	7.8 – 11.0 (IGT)
Diabetes	≥ 6.5%	≥ 7.0	≥ 11.1

• Situations where HbA1C cannot be used for diagnosis (conditions that affect red cell survival)
  • Hemoglobinopathies
  • Haemolytic anaemia
  • Untreated iron deficiency anaemia
  • Suspected gestational diabetes
  • Children
  • HIV
  • Chronic kidney disease
  • Medication that can cause hyperglycaemia e.g., corticosteroids