Some people buy tadalafil online without a prescription. That’s not to say there aren’t just as many illegitimate sites. It depends on the platform and insurance provider. Payment options: Consider how you’d like to pay. Never purchase ED medications from a site or service that doesn’t require a prescription and medical documentation.CIALIS for Use as Needed. Creatinine clearance 30 to 50 mL/min: A starting dose of 5 mg not more than once per day is recommended, and the maximum dose is 10 mg not more than once in every 48 hours. Creatinine clearance less than 30 mL/min or on hemodialysis: The maximum dose is 5 mg not more than once in every 72 hours [see . The normal dosage of Cialis for occasional use in treating ED is 10 mg taken before sexual activity. If you have side effects with the mg dose, your doctor may prescribe a 5-mg dose. If the Tadalafil 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). It is sometimes known by its generic name tadalafil, and sometimes known by its trade name, Cialis. There are also other brands of this medicine available.