In an obese 58-year-old patient with mild fatigue, normal hematocrit, normal thyroid‑stimulating hormone, fasting glucose of 128 mg/dL, and cholesterol of 289 mg/dL, what is the most likely diagnosis?

Type 2 Diabetes Mellitus

The most likely diagnosis is type 2 diabetes mellitus (option d), as this obese 58-year-old patient has a fasting glucose of 128 mg/dL, which meets diagnostic criteria for diabetes when confirmed on a subsequent day. 1, 2

Diagnostic Reasoning

Why Type 2 Diabetes is the Answer

• The fasting glucose of 128 mg/dL exceeds the diagnostic threshold of ≥126 mg/dL (7.0 mmol/L) for diabetes mellitus. 1, 2 According to American Diabetes Association guidelines, a fasting plasma glucose ≥126 mg/dL on two separate occasions is diagnostic for diabetes. 1

• The patient's clinical profile strongly supports type 2 diabetes: obesity (a major risk factor), age 58 years (type 2 diabetes typically develops after middle age), and the combination of elevated fasting glucose with hyperlipidemia (cholesterol 289 mg/dL). 1, 3

• Type 2 diabetes accounts for 90-95% of all diabetes cases in adults and is characterized by insulin resistance combined with beta-cell failure, strongly associated with obesity and sedentary lifestyle. 1, 3

Why the Other Options are Incorrect

Hypothyroidism (option a) is ruled out:

• The TSH of 3.2 is within normal range (typically 0.4-4.0 mIU/L), excluding thyroid dysfunction as the cause of fatigue. 1

Anemia (option b) is ruled out:

• The hematocrit of 49% is normal (normal range for men: 41-50%, women: 36-44%), excluding anemia as a cause of fatigue. 1

Depression (option c) is less likely:

• While depression can cause fatigue, the objective laboratory finding of elevated fasting glucose provides a clear metabolic explanation for the symptoms. 1
• The presence of multiple metabolic abnormalities (hyperglycemia and hyperlipidemia) in an obese patient points toward a metabolic syndrome/diabetes diagnosis rather than a primary psychiatric condition. 1

Critical Next Steps

Confirmation testing is required before making a definitive diagnosis. The American Diabetes Association recommends that all positive results must be confirmed on a subsequent day with repeat testing, unless the patient presents with unequivocal hyperglycemia (≥200 mg/dL with classic symptoms). 2, 1

The patient should be screened for cardiovascular risk factors, as patients with hypertension or hyperlipidemia should be screened for diabetes, and this patient already has hyperlipidemia. 1

Lifestyle counseling should begin immediately, as patients at increased risk of diabetes should be counseled on effective strategies to lower their risk, such as weight loss and exercise. 1