Viagra is the medication which is prescribed for treating impotence or erectile dysfunction, the inability to get or maintain erection for the sexual intercourse. Viagra can be available only by prescription. At the same time, there are a lot of pharmacological website nowadays where you can buy Viagra online. You should remember that you are not alone in your problem. Erectile dysfunction is popular disorder in men and from time to time it can happen even with the healthy men. That is why, for your own safety you should better consult your doctor and find out if you are able to take it too and in what dosage. If you still want to manage without the doctor's recommendations and buy Viagra without prescription, you must be aware at least of the following warnings: 1. You may need lower dose or may be not allowed to take Viagra if you have problems with the blood pressure and heart and take alpha blockers to treat them. 2. You are not allowed to take Viagra with other medicines which cause erection or contain the same main component. 3. You may need lower dose if you are older than 65 years. 4. You may need lower dose if you have problems with kidney or liver. 5. You may need lower dose if you take nitrates. To order Viagra online, search for it on special pharmacological websites. Talk to your doctor about your health firstly, in order to have safe and effective treatment.