Tadalafil can lower blood pressure because it relaxes blood vessels. With 40 mg, the effect can be more noticeable, particularly if you already have low blood pressure or take medicines that lower BP. The prescribing information specifically warns about hypotension from tadalafil's vasodilating effects. D DailyMed +1 A few important points: 40 mg is a high dose for ED. For erectile dysfunction, tadalafil is generally dosed much lower; 40 mg once daily is the standard dose for pulmonary arterial hypertension, not routine ED treatment. D DailyMed Avoid tadalafil with nitrate medicines (e.g., nitroglycerin/isosorbide), as the combination can cause a potentially dangerous BP drop. D DailyMed Be particularly cautious with alpha-blockers, blood-pressure medicines, and substantial alcohol, which can add to the BP-lowering effect. If you develop severe dizziness, fainting, chest pain, or unusual weakness, seek urgent medical attention. If you tell me your usual BP (for example, 120/80) and what medicines you take for BP/heart problems, I can tell you how concerning 40 mg would be in your situation.