Tadalafil (Cialis): Uses, Dosage, and Safety

Want to know why people call tadalafil the “weekend pill”? A single dose can help erections for up to 36 hours, which makes timing easier than some other ED drugs. But that long effect also means you should know how to use it safely.

How tadalafil works and who it helps

Tadalafil is a PDE5 inhibitor. That means it relaxes blood vessels to increase blood flow to the penis during sexual arousal. Doctors prescribe it mainly for erectile dysfunction (ED). It’s also approved for pulmonary arterial hypertension (PAH) under a different brand and can help relieve urinary symptoms from an enlarged prostate (BPH).

For ED, tadalafil works when you’re sexually stimulated — it won’t cause an erection on its own. For PAH or daily ED treatment, the effect is steady because of daily dosing.

How to take tadalafil

There are two common ways to use tadalafil: as-needed and daily. The typical as-needed dose is 10 mg taken at least 30 minutes before sex; some people use 20 mg. If side effects are a problem or you need regular readiness, daily dosing at 2.5–5 mg once a day is common. For PAH, doctors usually prescribe 40 mg once daily (brand name Adcirca).

You can take tadalafil with or without food. Alcohol can increase side effects like dizziness and low blood pressure, so keep drinking moderate. If you’re older or have other health issues, your doctor may start at a lower dose.

Never mix tadalafil with nitrates (nitroglycerin or similar). That combo can cause dangerously low blood pressure. Also be careful with alpha-blockers, strong CYP3A4 inhibitors (like ritonavir or ketoconazole), and certain antibiotics — they can raise tadalafil levels and the risk of side effects.

Side effects & safety

Common side effects are headache, flushing, indigestion, stuffy nose, back pain, and muscle aches. These usually go away within a day or two. Serious reactions are rare but need immediate attention: sudden vision loss, sudden hearing loss, chest pain, fainting, or an erection lasting more than 4 hours (priapism).

If you have heart disease, recent stroke, low blood pressure, or take nitrates, don’t use tadalafil without talking to your doctor. If you have liver or kidney problems, dose adjustments might be needed.

Thinking of buying tadalafil online? Use a licensed pharmacy that asks for a prescription and has a real pharmacist contact. Avoid sites that sell without a prescription, offer suspiciously low prices, or use vague addresses. Scams sell fake pills that can be dangerous.

Quick checklist: get a medical check-up first, start at the lowest effective dose, avoid nitrates and heavy drinking, watch for serious side effects, and only buy from reputable sources. When used correctly, tadalafil is a convenient and effective option for many people with ED or PAH.