Do not mix the liquid with other medications or add anything to flavor the medication. This medicine comes with a patient information leaflet. Do not take a double dose to make up for a missed one. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. What should I do if I forget a dose? This increased blood flow can cause an erection.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 prescription drug that’s used in. Viagra is available in three strengths: 25 milligrams (mg), 50 mg, and mg. Note: Sex and gender exist on spectrums. Use of the term “male” in this article refers to sex assigned at birth.  · For oral dosage forms (suspension or tablets): Adults—20 milligrams (mg) 3 times a day. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 80 mg 3 times a day. Children 1 year of age and older weighing 45 kilograms (kg) or more—20 mg 3 times a day.