It is your doctor who decides what is the dose of Viagra that suits you best. For most men, it is 50 mg. But for some, the doctor will prescribe a lower dose or higher. Never take a higher dose than you were prescribed. Viagra is taken when needed, about an hour before intercourse. The tablet should be swallowed whole shot with a little water. Do not use Viagra more than once per day. Viagra promote the erection if you are sexually stimulated. In the absence of sexual stimulation, it produces no erection. The time required for viagra to act varies from one man to another, it usually takes half an hour to an hour. You may find it takes a little longer if you take the medication during a meal. Alcohol can temporarily prevent you from having an erection. To get the best possible effect of your medicine, you should be careful not to drink large amounts of alcohol before taking Viagra. Viagra does not help if your erection or if your erection does not last long enough to allow you to have full sexual intercourse, make it to your doctor. Do not change the prescribed dose or duration of treatment. If you think the effect of the drug is insufficient or too strong, talk to your doctor or pharmacist. Special considerations for patients older than 65 years. If you belong to this age, your initial dose of Viagra will be adjusted (typically 25 mg). Special considerations for patients with kidney or liver disease If you have a disorder of hepatic or renal function, inform your doctor. He will decide if it is necessary that you take a dose of Viagra lowest. What happens if you take too many tablets? A dose of more than 100 mg does not increase efficacy, resulting in only a frequency and greater severity of adverse effects. Do not take a dose of Viagra than your doctor has prescribed If you take more tablets than prescribed by your doctor, tell him.