What Is Tadalafil? A Complete Guide

What Is Tadalafil?

Tadalafil is a prescription medication used to treat erectile dysfunction (ED). It belongs to a class of drugs called PDE5 inhibitors, which work by increasing blood flow to the penis during sexual arousal. It is the generic version of Cialis, one of the most prescribed ED medications in the US.

Tadalafil is sometimes called "the weekend pill" because a single dose remains effective for up to 36 hours — far longer than sildenafil (Viagra's generic), which lasts 4–6 hours. This extended window means you can take it the night before or in the morning without needing to time sex to a specific hour.

Beyond ED, tadalafil is also FDA-approved for benign prostatic hyperplasia (BPH, or enlarged prostate) and pulmonary arterial hypertension. For ED, it's available in two formats: as-needed doses (10mg or 20mg) or a daily low dose (2.5mg or 5mg).

Since Eli Lilly's US patent on Cialis expired in 2018, generic tadalafil has been available from multiple manufacturers. Generic prices are typically $2–5 per dose, compared to $50–70 for branded Cialis at retail.

How Tadalafil Works

Tadalafil works by inhibiting an enzyme called phosphodiesterase type 5 (PDE5). Here's the simplified version of what that means:

When you're sexually aroused, your nervous system releases nitric oxide in the blood vessels of the penis. Nitric oxide triggers the production of a molecule called cGMP, which relaxes smooth muscle and allows blood to flow in, causing an erection. PDE5 is the enzyme that breaks down cGMP — so by inhibiting PDE5, tadalafil allows cGMP to accumulate and blood flow to increase.

The key point: tadalafil does not cause an erection on its own. It requires sexual stimulation to work. Without arousal, there's no nitric oxide release and the drug has no effect. This is true of all PDE5 inhibitors, including sildenafil.

Tadalafil takes 1–2 hours to reach full effect after dosing. Its longer duration compared to sildenafil is due to its longer half-life — approximately 17.5 hours, meaning it stays in your system long after the initial dose. For a more detailed look at the mechanism, see our how does Cialis work guide.

Tadalafil Dosage Guide

Tadalafil comes in four doses: 2.5mg, 5mg, 10mg, and 20mg. Which dose you use depends on whether you're taking it on demand or daily.

Most men starting tadalafil are prescribed 10mg as-needed. If 10mg doesn't work well, the dose can be increased to 20mg. If side effects are an issue, it can be reduced to 5mg. Your prescribing physician will recommend the right starting dose based on your health history.

Daily dosing (2.5–5mg) maintains a steady level of tadalafil in your system. You take one pill at the same time each day, regardless of sexual activity. This eliminates any planning — you're always ready. Some men also find that daily low-dose use produces milder side effects than higher as-needed doses, because the drug level stays lower and more constant.

You should not take more than one dose within 24 hours, and no more than 20mg in any 24-hour period. Tadalafil is not affected by food — you can take it with or without a meal.

Side Effects

Tadalafil is well-tolerated by most men. Side effects are typically mild and temporary, peaking as the drug reaches maximum concentration and fading as it clears your system.

The back pain and muscle aches are more characteristic of tadalafil than sildenafil, and are related to tadalafil's longer half-life. They typically appear 12–24 hours after dosing and resolve within 48 hours. At lower doses (5mg daily), this side effect is less common.

Do not take tadalafil if you use nitrates (nitroglycerin, isosorbide) for heart conditions. The combination can cause a dangerous, potentially fatal drop in blood pressure. Always disclose all medications during your consultation.

Generic Tadalafil vs Branded Cialis

Generic tadalafil contains the exact same active ingredient at the same dose as branded Cialis. The FDA requires generics to be bioequivalent — meaning the drug is absorbed and acts in the same way. There is no meaningful clinical difference between generic tadalafil and Cialis.

The difference is cost. Branded Cialis retails for $50–70 per pill without insurance. Generic tadalafil from online telehealth platforms costs $2–5 per dose — or ~$39–45/month for daily dosing. The savings are significant with no trade-off in effectiveness.

All major telehealth platforms — Roman, Hims, Ro, and Rex MD — prescribe generic tadalafil, not branded Cialis. If a platform is advertising "Cialis," verify whether they mean the brand or the generic.

How to Get Tadalafil Online

Tadalafil requires a prescription, but you don't need to visit a doctor's office or schedule a video call. Licensed US telehealth platforms let you complete an online medical questionnaire — covering your health history, current medications, and symptoms — which a licensed physician reviews and either approves or follows up on. The whole process typically takes a few hours.

Once prescribed, your medication ships directly to you in discreet packaging. Platforms like Roman offer free 2-day shipping. Rex MD is the cheapest option for generic tadalafil.

See our full platform comparisons:

Frequently Asked Questions