Tadalafil is mainly used for the treatment of erectile dysfunction and its proper usage includes both on-demand and regular daily dosage. 1. On-demand: Men suffering from erectile dysfunction can use tadalafil on-demand. That is to say, take tadalafil before sexual intercourse, so that the penis can be erected normally under the situation of sexual stimulation, so as to complete sexual intercourse successfully. 2. Regular daily use: Erectile dysfunction patients can also take tadalafil at the same time every day, without thinking about when to have sex, regular use of the drug can improve the erectile function of patients with different degrees of erectile dysfunction, and the drug is well tolerated. Common adverse reactions caused by tadalafil include headache, dyspepsia, nasal congestion, limb pain, back pain, and flushing. Tadalafil should not be used by people who are allergic to tadalafil, or who are taking nitrates or guanylate cyclase stimulators; if prolonged erection and other discomforts occur after using the medication, it is important to seek medical attention. Individuals need to follow the doctor’s instructions for the correct use of tadalafil and should not abuse the drug.