Talk to your doctor about which dosing schedule is right for you. Do not take a double dose to make up for a missed one. It works to treat erectile dysfunction by increasing blood flow to the penis during sexual stimulation. If you drink a large amount of alcohol more than five glasses of wine or five shots of whiskey while you are taking tadalafil you are more likely to experience certain side effects of tadalafil such as dizziness, headache, fast heartbeat, and low blood pressure. BPH occurs when the prostate and the surrounding tissues become enlarged. Do not divide the 40 mg dose. Tadalafil is sometimes taken as needed, usually at least 30 minutes before sexual activity and not more often than once every 24 hours. · Taking higher dosages of Cialis than this, such as 40 mg per day, raises your risk for serious side effects. Examples of these side effects include very low blood .  · Adults—5 milligrams (mg) once a day, taken at the same time each day, without regard for the timing of sexual activity. Children—Use is not recommended. For . Is a mg dose of Cialis safe to take? No, 40 milligrams (mg) is not a safe dose of Cialis to take. The maximum recommended dosage of Cialis is 20 mg once per .