Hi welcome to healthcare magic A successful erection involves the central nervous system ( brain and spinal cord), hormonal systems, peripheral nervous system ( nerves outside the brain and spinal cord) and the blood vessels and blood supply to the penis Erectile dysfuntion is associated with diabetes, hypertension, high cholesterol, damage to the blood vessels and nerves due to trama from activities such as long distance cycling, kidney disease,liver disease, stroke, abnormal thyroid function, anxiety, stress, depression, relationship discord, poor nutrition. It can also be a side effect of some medications such : some antihypertensives, antidepressants, some medications for gastric ulcers Some patients may require laboratory testing, a doctor will determine that based on the history. Part of the treatment actually involves lifestyle modification ( exercise, healthy diet, weight loss) because ED can be associated with heart disease. Viagra and the other medications like it, can be used if there are no contraindications which would be the use of nitrates ( if you are taking any nitrate medication then you cannot use it because it would cause an extreme drop in blood pressure.) You should speak to your doctor first to find out if you are a good candidate for viagra I hope this helps you