Viagra (sildenafil) is a great help for people diagnosed with ED. ED is a condition when the patient is unable to achieve a satisfactory erection and is therefore unable to have sex. Take Viagra exactly as prescribed by your health care provider. This medicine is supposed to be taken on the «when needed» basis, so you do not have to worry about missing a dose. Taking two doses at once will not improve your sexual ability. If you take Viagra it doesn’t mean you will be able to get an erection without any sexual stimulation. Sexual stimulation is required to obtain an erection and have sex. Discuss your diet with your health care provider, as you may be advised not to drink grapefruit juice or any food that contains grapefruit. If you think you need a dose adjustment talk to your health care provider before changing your dose of Viagra.