Can Sildenafil Cause Blood in Urine?
Sildenafil does not cause hematuria (blood in urine) based on extensive clinical trial data and guideline evidence. The documented side effects of sildenafil are primarily vasodilatory in nature—headache, flushing, dyspepsia, and epistaxis (nosebleeds)—but hematuria is not among them 1.
Evidence from Major Clinical Trials
The SUPER-1 trial, which studied 278 patients with pulmonary arterial hypertension taking sildenafil at doses of 20-80 mg three times daily for 12 weeks, specifically documented side effects as headache, flushing, dyspepsia, and epistaxis—with no mention of hematuria 1. This represents the highest quality evidence for sildenafil's adverse effect profile, as it was the pivotal FDA approval trial.
Multiple large randomized controlled trials evaluating sildenafil in men with erectile dysfunction, including those with cardiovascular disease, diabetes, and hypertension, consistently report the same vasodilatory side effects without documenting hematuria as an adverse event 2, 3, 4.
Why Epistaxis But Not Hematuria?
The documented occurrence of epistaxis (nosebleeds) with sildenafil reflects its vasodilatory mechanism affecting superficial mucosal vessels in the nasal passages 1. However, this vasodilatory effect does not translate to urinary tract bleeding. The urinary system lacks the same superficial vascular bed susceptible to the mild vasodilation caused by PDE5 inhibition.
Important Clinical Caveat
If a patient on sildenafil presents with hematuria, investigate alternative causes rather than attributing it to the medication 1. The differential diagnosis should include:
- Urinary tract infection or inflammation
- Kidney stones
- Bladder pathology (including malignancy, especially in older men with risk factors)
- Prostate disease (benign prostatic hyperplasia or prostate cancer)
- Glomerular disease
- Anticoagulant use or bleeding disorders
The JNC 7 guidelines emphasize that urinary outflow obstruction symptoms should be elicited as part of the hypertension workup, and many men with erectile dysfunction have concurrent lower urinary tract symptoms that may independently cause hematuria 1.
Safety Profile in High-Risk Populations
Sildenafil has been extensively studied in men with multiple comorbidities—including hypertension, diabetes, cardiovascular disease, and chronic kidney disease—without hematuria emerging as a safety concern 2, 3, 5, 6, 4. A retrospective analysis of 357 patients with ischemic heart disease taking sildenafil showed adverse event profiles similar to those without heart disease, with no mention of urinary bleeding 2.
Bottom Line
Hematuria in a patient taking sildenafil warrants standard urological evaluation, not medication discontinuation based on presumed drug causation. The extensive clinical trial database and guideline literature do not support sildenafil as a cause of blood in urine 1, 2, 3.