It's mostly based on history of symptoms such as trouble getting an erection, trouble keeping an erection and reduced sexual desire. Tests are done to know the presence of any organic causes.

Supplements with DHEA, L-arginine, Ginseng and Propionyl-L-carnitine are studied to have some positive results and also generally safe.

It depends on the cause of erection issue. In general; good balanced diet, regular exercise, normal BMI, no smoking or alcohol, adequate sleep and control of mental stress will help.