If you need emergency medical care for a heart problem, it will be important for your health care provider to know when you last took Cialis. Talk to your doctor about which dosing schedule is right for you. Do not take more or less of it or take it more often than prescribed by your doctor. Ask your doctor if you are not sure whether any of your medications contain nitrates. What special dietary instructions should I follow? After taking a single tablet, some of the active ingredient of Cialis remains in your body for more than 2 days.Tadalafil (Cialis) is a medicine used to treat erectile dysfunction (ED, also called impotence) and problems with urination caused by an enlarged prostate (benign prostatic hypertrophy or BPH). Tadalafil works by helping to relax the blood vessels in the penis, allowing blood to flow into the penis, and causing an erection. Dosage range: mg to 5 mg. Frequency: once daily, regardless of the timing of sexual activity. Cialis’s recommended dosage when it’s taken as needed for ED is as follows. Dosage range: 5 mg to 20 mg. Frequency: one dose at least 30 minutes before sexual activity, with a maximum of one dose per day*. Roman is a telehealth prescription service and online pharmacy that provides prescription Cialis for ED and a host of other conditions, like hair loss, cold sores, and premature ejaculation. When.