This can happen if you are sick with fever, diarrhea, or vomiting; sweat a lot; or do not drink enough liquids. What should I do if I forget a dose? If you are taking sildenafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. Do not take more or less of it or take it more often than prescribed by your doctor. If you become pregnant while taking sildenafil, call your doctor. This increased blood flow can cause an erection.Before taking sildenafil, tell your doctor and pharmacist if you are allergic to sildenafil, any other medications, or any of the ingredients in sildenafil tablet or suspension. Ask your . What to consider Cost Overdose Ask your doctor Q&A Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a . You should not take Viagra more than once daily. And you should only take it as needed. Long-term use.