Levitra 20mg (vardenafil) is a medication used to treat erectile dysfunction (ED). It works by increasing blood flow to the penis to help achieve and maintain an erection. Levitra typically comes in 2.5 mg, 5 mg, 10 mg, and 20 mg doses. The 20 mg dose is often prescribed for those who need a higher dosage, but it's essential to follow the prescribed amount. Common side effects include headaches, flushing, nasal congestion, upset stomach, and dizziness. Severe side effects are rare but can include vision or hearing loss, an erection lasting more than 4 hours (priapism), or an allergic reaction.