Repeat the Fasting Blood Sugar Test to Confirm Diagnosis
The first next step is to repeat the fasting blood sugar test (Option A) to confirm whether this patient has diabetes or prediabetes, as a single elevated FBS of 7.2 mmol/L (approximately 130 mg/dL) requires confirmation on a separate day before making a definitive diagnosis. 1
Why Confirmation Testing is Required
A single FBS measurement of 7.2 mmol/L (130 mg/dL) exceeds the diagnostic threshold for diabetes (≥7.0 mmol/L or 126 mg/dL), but in the absence of unequivocal hyperglycemia with acute metabolic decompensation, diagnostic criteria must be confirmed by repeat testing on a different day 1
This patient has only occasional fatigue and thirst—not the classic severe symptoms of uncontrolled diabetes (polyuria, polydipsia, unexplained weight loss)—so confirmation is mandatory before labeling him with a chronic disease diagnosis 1
The repeat test will definitively classify him into one of three categories: normal glucose tolerance (FBS <5.6 mmol/L or 100 mg/dL), prediabetes (FBS 5.6-6.9 mmol/L or 100-125 mg/dL), or diabetes (FBS ≥7.0 mmol/L or ≥126 mg/dL) 1
Alternative Diagnostic Tests to Consider
While repeating FBS is the most straightforward approach, you could alternatively use HbA1c ≥6.5% or a 2-hour 75-g oral glucose tolerance test (OGTT) ≥11.1 mmol/L (200 mg/dL) to confirm the diagnosis 1
HbA1c testing may be particularly useful in this patient as it reflects average glucose control over the preceding 2-3 months and doesn't require fasting 1
Why the Other Options Are Incorrect
Option B (Tell him to tolerate symptoms and return if worse) is dangerous and inappropriate:
- This dismisses a potentially serious metabolic condition in a high-risk patient (family history, obesity, symptomatic) 1
- Delaying diagnosis and treatment of diabetes leads to prolonged hyperglycemia exposure, which increases the risk of microvascular and macrovascular complications 1
- Even if he has prediabetes rather than diabetes, early intervention with lifestyle modification can prevent or delay progression to overt diabetes 1, 2
Option C (Start metformin immediately) is premature:
- You cannot initiate pharmacologic therapy without first confirming the diagnosis through repeat testing 1
- If the repeat test shows prediabetes (FBS 100-125 mg/dL), metformin may be considered for diabetes prevention, particularly given his BMI >30 kg/m², but this is a secondary consideration after diagnosis confirmation 1, 3
- If confirmed diabetes, metformin would indeed be first-line therapy, but the diagnosis must be established first 3, 4
What Happens After Confirmation Testing
If Repeat Testing Confirms Diabetes (FBS ≥126 mg/dL):
- Start metformin immediately as first-line pharmacologic therapy unless contraindicated, as it reduces hepatic glucose production and has cardiovascular benefits 3, 4
- Initiate comprehensive lifestyle modification including medical nutrition therapy, weight loss targeting 7% body weight reduction, and at least 150 minutes weekly of moderate-intensity physical activity 1
- Consider adding an SGLT2 inhibitor as dual therapy given the severity of hyperglycemia, which provides additional cardiovascular and renal protection 3
If Testing Shows Prediabetes (FBS 100-125 mg/dL):
- Refer to an intensive lifestyle modification program targeting 7% weight loss and 150 minutes weekly of moderate physical activity, which reduces diabetes risk by 58% 1
- Consider metformin for diabetes prevention given his BMI >30 kg/m², family history of diabetes, and symptomatic presentation, as metformin reduces diabetes incidence by 31% in high-risk individuals 1, 2
- Recheck FBS or HbA1c at least annually to monitor for progression to diabetes 1
Critical Pitfalls to Avoid
Never diagnose diabetes based on a single glucose measurement in the absence of severe hyperglycemic symptoms—this violates established diagnostic criteria and could lead to inappropriate lifelong disease labeling 1
Never dismiss symptoms in a high-risk patient (family history, obesity, elevated FBS)—even mild symptoms warrant thorough evaluation 1, 5
Never delay confirmation testing by weeks or months—repeat the test within days to establish the diagnosis promptly and initiate appropriate management 1
Ensure renal function (eGFR) is checked before starting metformin, as it is contraindicated when eGFR <30 mL/min/1.73 m² and requires dose reduction when eGFR is 30-45 mL/min/1.73 m² 6, 4