Viagra is a very common medication taken my men of all ages to help treat erectile dysfunction. This condition makes it difficult for men to achieve or sustain an erection. Viagra has remained a very popular choice ever since it first appeared in 1998 because it works quickly. Most men notice results within 30 minutes of taking a pill, although some find it works as fast as 15 minutes later. The oral tablets should be taken 2 hours after eating. However, this varies according to each individual and can be affected by various factors. For example, if you take the tablet right after eating a high-fat meal or you take it in combination with other medications, you may find that it does not work the same. Viagra continues to work for approximately 2 hours for most men, and as long as 3 or 4 hours for others.