A few of the conditions you should let your healthcare provider know about before you take sildenafil citrate include sickle cell anemia, multiple myeloma, leukemia, and high blood pressure. Among the people who should not take sildenafil citrate at all are those who are taking a nitrate for angina and those who are allergic to any component of sildenafil citrate. Some other precautions and warnings for sildenafil citrate include potential drug interactions and the risk of serious side effects such as a heart attack, stroke, or sudden death in some people taking this medicine.

• 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.