Viagra typically starts to work between 30 and 60 minutes after you take a dose of the drug. But Viagra itself doesn't give you an erection. Instead, you'll need to be sexually aroused in order for the drug to work.

Do not consume grapefruit or grapefruit products while taking Viagra, and consider Taking Viagra with marijuana /?amp=1

Viagra keeps working in your body for up to 5 hours. This means that if you’re aroused, you should be able to achieve an erection for up to 4 hours after taking a dose of Viagra.

Even though Viagra keeps working in your body for several hours, your erection shouldn't last this long. In fact, rarely, Viagra can cause priapism. With this condition, you have a long-lasting and sometimes painful erection.