What comprehensive bloodwork is recommended for a 67-year-old male with erectile dysfunction (ED) who has tried Cialis (tadalafil) and Viagra (sildenafil)?

Comprehensive Bloodwork for ED After Failed PDE5i Therapy

Order morning serum total testosterone as the essential test, then add fasting glucose or HbA1c and a lipid panel to screen for cardiovascular disease and diabetes—the two most critical underlying conditions affecting both ED treatment response and long-term mortality. 1, 2

Core Laboratory Tests

Mandatory Testing

• Morning serum total testosterone is the only laboratory test with a moderate-strength recommendation from the American Urological Association for all men presenting with ED 1
  • Must be drawn in the morning when testosterone levels are highest 1
  • Low testosterone may explain poor response to PDE5 inhibitors and requires separate management 2

Strongly Recommended Additional Tests

• Fasting glucose or HbA1c should be ordered because diabetes significantly reduces PDE5i efficacy—men with diabetes respond less robustly to sildenafil, tadalafil, and vardenafil compared to the general ED population 1

  • Diabetic men have more severe ED at baseline and require more aggressive management 1

• Lipid profile (total cholesterol, LDL, HDL, triglycerides) is critical because ED serves as a risk marker for cardiovascular disease as strong as cigarette smoking or family history of myocardial infarction 1, 2

  • The Princeton Consensus Conference identified ED as a substantial independent predictor of future cardiac events 1
  • This represents a pivotal opportunity to prevent cardiovascular morbidity and mortality 1

Clinical Reasoning

The AUA guidelines explicitly state that "selective laboratory testing" should be performed, with only testosterone receiving a specific moderate recommendation 1. However, the guidelines emphasize that ED is a cardiovascular risk marker requiring evaluation of underlying conditions 1, 2.

Common pitfall: Ordering testosterone alone misses the opportunity to identify life-threatening cardiovascular disease and diabetes that directly impact both ED treatment success and patient survival 1, 2.

Additional Considerations Based on History

• Renal function (creatinine, eGFR) if there is any history suggesting kidney disease, as PDE5 inhibitors require dose adjustment in moderate-to-severe renal impairment 1

• Liver function tests (AST, ALT) if there is suspicion of hepatic disease, as severe liver disease contraindicates PDE5i use 1

• Thyroid function (TSH) if clinical signs of thyroid dysfunction are present, though this is not routinely recommended 1

Why This Matters for Treatment

At age 67 with failed trials of both tadalafil and sildenafil, identifying underlying conditions is essential because:

• Low testosterone may require replacement therapy for PDE5i to work effectively 2
• Uncontrolled diabetes reduces PDE5i efficacy by approximately 20-30% 1
• Cardiovascular disease may require risk stratification before continuing sexual activity 1
• These conditions affect quality of life and mortality far beyond sexual function 1, 2