Sildenafil dosage: what dose works and how to use it

One pill can change a night — but dose, timing, and interactions decide the result. This quick guide tells you the usual sildenafil doses, when to take each one, and the safety points most people miss.

Typical doses and when they’re used

For erectile dysfunction (ED): the common starting dose is 50 mg taken as needed about 30–60 minutes before sex. Doctors may lower it to 25 mg if you’re older, have certain health problems, or take interacting drugs. They may raise it to 100 mg if 50 mg doesn’t work and you tolerate it well. You should not take more than 100 mg in 24 hours.

For pulmonary arterial hypertension (PAH): sildenafil is given in much smaller, regular doses (often 20 mg three times a day under the brand name Revatio). That schedule is different because PAH needs steady blood levels, not single higher doses.

How to take sildenafil the right way

Take sildenafil by mouth with water. It works faster on an empty stomach. A heavy, high-fat meal can delay how quickly it starts—sometimes by an hour or more. Alcohol in large amounts can reduce effectiveness and increase side effects like low blood pressure or dizziness.

Do not take sildenafil more than once a day for ED. For PAH, follow your doctor’s exact timing (usually three times daily). If you miss a dose for PAH, skip it and resume your normal schedule—don’t double up.

What to watch for: common side effects include headache, flushing, nasal congestion, upset stomach, and vision changes (blue tint or blurred vision). These often go away on their own. If you get sudden chest pain, severe dizziness, fainting, or an erection lasting longer than 4 hours, seek emergency help immediately.

Adjustments you should know about: people with moderate-to-severe liver or kidney problems usually need a lower starting dose. Older adults may also start lower. If you take certain medicines that affect liver enzymes (like some HIV drugs, antibiotics, or antifungals), your doctor might lower your dose or recommend a different plan.

Big interaction to avoid: nitrates. If you use any nitrate medicine (nitroglycerin, isosorbide), do NOT take sildenafil — the combo can cause a dangerous drop in blood pressure. Be careful with alpha-blockers too; your doctor may adjust timings to reduce lightheadedness.

Final practical tips: start at 50 mg for ED unless your doctor says otherwise; try it a few times—one dose may not be enough to judge; keep a simple log of dose and effects to discuss with your prescriber. Always get sildenafil from a licensed pharmacy and talk to your doctor about other meds and health conditions before starting.