Viagra (sildenafil) is used by males of any age to treat impotence no matter what it was caused by. This drug is supposed to be taken exactly as recommended without exceeding the dose prescribed. Viagra should be taken only if you do not have contraindications and the benefits of the treatment outweigh potential risks. You may want to discuss with your health care provider any medical conditions you have, such as bleeding disorder, chest pain, high cholesterol, stomach ulcer, blood cell problems, diabetes, pulmonary veno-occlusive disease, stroke, heart, kidney, or liver disease, high or low blood pressure, heart attack, conditions affecting the shape of the penis, irregular heartbeat, or blood circulation problems, as they can affect the dose you are prescribed. Please make sure you take Viagra not more often than every 24 hours, as otherwise it may cause overdose symptoms Mild side effects that do not need to be reported to your doctor include diarrhea, muscle aches, flushing, insomnia, headache, nosebleeds, changes in color vision, numbness, burning, or tingling, light sensitivity, and heartburn.