Tadalafil: What It Is and How to Use It Safely

A single 5 mg pill of tadalafil can work for up to 36 hours — that’s why many people call it the "weekend" erectile dysfunction drug. But duration is only one part of the story. This short guide gives clear, useful facts about what tadalafil treats, how it works, dosing options, safety issues, and smart tips if you plan to buy it online.

Tadalafil treats erectile dysfunction (ED) and symptoms of benign prostatic hyperplasia (BPH). Another formulation and dose treat pulmonary arterial hypertension (PAH). For ED you can use tadalafil as needed before sex or as a daily low-dose tablet. Doctors pick the plan based on how often you are sexually active, your health, and other medicines you take.

How it works and typical doses

The way tadalafil works is straightforward: it blocks an enzyme called PDE5, which helps relax blood vessels and improves blood flow to the penis during arousal. For ED, common doses are 10 mg or 20 mg taken before sex. If you want to be ready more often, a daily dose of 2.5 mg or 5 mg may be prescribed. For BPH the usual dose is 5 mg once daily. PAH uses a different dosing schedule under specialist care. Never mix dosing strategies without talking to your prescriber.

Side effects, risks, and buying tips

Side effects are usually mild but real. You may get headache, indigestion, back or muscle pain, flushed skin, or a stuffy nose. These often pass in a day or two. Serious signs that need immediate care include chest pain, sudden vision loss, sudden hearing loss, fainting, or an erection lasting more than four hours. The biggest drug interaction to avoid is nitrates for chest pain — combining nitrates and tadalafil can cause a dangerous drop in blood pressure. Other interactions to watch for include alpha-blockers, some antibiotics, HIV and antifungal drugs, and certain heart medicines. Tell your doctor about all prescriptions, over-the-counter meds, and supplements you use.

If you have heart disease, low blood pressure, recent stroke, severe liver or kidney problems, or use recreational drugs that affect circulation, discuss risks before starting tadalafil. Pregnant or breastfeeding women don’t use tadalafil; it’s for men or people assigned male at birth for ED and some PAH cases.

Buying tadalafil online is common, but safety varies. Prefer online pharmacies that require a prescription, show clear contact information, and list proper licensing. Avoid sites that promise no prescription needed, sell at prices that seem too good to be true, or hide shipping and return policies. Read reviews, check for pharmacy accreditation, and save a copy of your prescription.

Practical tips: start with the lowest dose your doctor suggests, avoid heavy alcohol before sex, and take note of side effects during the first few tries. Keep a medication list for your provider and don’t mix tadalafil with nitrates. If side effects are persistent or you don’t get the expected result, talk to your doctor about changing dose or trying another medication.

See our buyer guides and detailed pharmacy drug comparisons.