Clerking diabetes (type 2) in adults

History Taking

Type 2 diabetes is most often diagnosed on routine screening. In clerking diabetes, the following approach may be used:

Establish a firm diagnosis using either of the following tests (verified by repeat testing, preferably with the same diagnostic test):

  • Fasting plasma glucose (FPG) >6.9 mmol/L (>125 mg/dL) (most commonly used)
  • Random plasma glucose ≥11.1 mmol/L (≥200 mg/dL) with diabetes symptoms such as polyuria, polydipsia, fatigue, or weight loss
  • 2-hour post-prandial glucose ≥11.1 mmol/L (≥200 mg/dL) on a 75 g oral glucose tolerance test
  • HbA1c ≥48 mmol/mol (≥6.5%).

Evaluate the presence of risk factors for type 2 diabetes.

  • Older age;
  • overweight/obesity;
  • black, Hispanic, or Native American ancestry;
  • family history of type 2 diabetes;
  • history of gestational diabetes;
  • physical inactivity;
  • hypertension;
  • dyslipidaemia;
  • known cardiovascular disease.

Exclude type 1 diabetes, because prompt initiation of insulin treatment is mandatory for this condition. Type 1 diabetes can occur at any age, but usually is diagnosed in younger (age <35 years), thinner patients and has a more rapid onset and often more severe symptoms.

Ask for other diagnostic factors and complications of type 2 diabetes:

  • candidal infections; most commonly vaginal, penile, or in skin folds
  • skin infections; cellulites or abscesses
  • urinary tract infections; cystitis or pyelonephritis
  • fatigue
  • blurring of vision
  • paraesthesias
  • polydipsia
  • polyphagia
  • polyuria
  • nocturia
  • frothiness of urine
  • erectile dysfunction
  • unintentional weight loss

Physical examination

General examination

  • Check for fever: from recurrent infections due to immunosuppression.
  • Examine for pallor which may be due to diabetic nephropathy.
  • Assess for dehydration due to excessive fluid loss from polyuria.
  • Check for limb edema from nephropathy or heart failure secondary to diabetes.

Systemic examination

Nervous system examination should include assessment of ankle reflexes, pulses, vibratory sensation, and monofilament touch sensation, and a dilated retinal examination.

Cardiovascular system examination should check for pulse rate, raised blood pressure and displaced apex beat (all suggestive of concomitant cardiovascular disease).

Skin examination may show acanthosis nigricans (a velvety, light brown-to-black marking, usually on the neck, under the arms, or in the groin, usually associated with obesity).


1st line: 

  • HbA1c: 48 mmol/mol (6.5%) or greater is diagnostic.
  • Fasting Blood Glucose: >6.9 mmol/L (>125 mg/dL) is diagnostic.
  • Random Blood Glucose: ≥11.1 mmol/L (≥200 mg/dL) is diagnostic.
  • 2 hours post-prandial glucoseafter 75 g oral glucose: ≥11.1 mmol/L (≥200 mg/dL) is diagnostic.

Other investigations:

  • Fasting lipid profile: may show high LDL, low HDL, and/or high triglycerides
  • Urine ketones: negative in type 2 DM.
  • Urinary albumin excretion: may be increased.
  • Serum creatinine and estimated GFR: may show renal insufficiency
  • ECG: may indicate prior ischaemia. A normal ECG does not however, rule out coronary artery disease.