There are many precautions and warnings for Viagra to be aware of. For example, among the conditions you should let your healthcare provider know about before you take Viagra are leukemia, sickle cell anemia, high blood pressure, and liver disease or liver failure. Also, Viagra can interact with certain other medications (such as alpha blockers), and it does not provide any protection against sexually transmitted diseases. Be sure to talk with your healthcare provider about any Viagra precautions and warnings that may apply to you.

• Heart disease or blood vessel disease
• Liver disease or liver failure
• A history of a heart attack, stroke, or life-threatening arrhythmia within the past six months
• Retinitis pigmentosa, which is a rare eye problem
• Low blood pressure (hypotension)
• High blood pressure (hypertension)
• Sickle cell anemia
• Multiple myeloma
• Leukemia
• A history of priapism, which is a painful erection lasting longer than six hours
• Any condition that causes a penis deformation, such as angulation, Peyronie's disease, or cavernosal fibrosis
• Any allergies.