Before one is given Viagra, the doctor takes some history to give you the right prescription. Tell the doctor if you are allergic to any medication, if you smoke, have ever had an erection that lasted for several hours, stomach ulcer, heart, kidney, or liver disease, heart attack, irregular heartbeat, a stroke, chest pain, high or low blood pressure, sickle cell anaemia, leukaemia, diabetes, or conditions affecting the shape of the penis. Having any of these can make taking Viagra dangerous.
Attribution: Straight Talk Foundation