Viagra has been taken my millions of men worldwide to help them achieve a longer and harder erection during sexual intercourse. The results of taking the small blue pill vary per individual. However, Viagra tends to work as quickly as 30 minutes after taking the drug. When using in combination with sexual stimulation, the effects of Viagra can last as long as 5 hours, although 3-4 hours is more common. Most men find that the effects of the pill begin to wear off after a couple of hours. Certain factors will also affect how long Viagra lasts in your system, making the effects stronger. These include your age, as the pill will remain in your body longer if you are older than 65, having severe kidney or liver disease or certain other medications you are taking at the same time. Factors that will reduce the amount of time Viagra remains in the body are taking the pill right after eating a high-fat meal or taking it with certain medications such as rifampin that interact with Viagra. That is why you should always consult with your doctor before taking Viagra.