Please understand that ED can be an early indicator of cardiovascular disease or diabetes and that, if not done so already, it is strongly advised that you consult your GP within 6 months for a clinical review of potential underlying conditions and risk factors associated with ED. Erectile dysfunction (ED), is the inability to achieve or obtain or sustain an erection long or hard enough for sexual intercourse. SIldenafil works for men with ED by helping to relax the blood vessels in the penis, allowing blood to flow into the penis when sexually stimulated.