How Viagra Works and When to Take It
Sildenafil (the active ingredient in Viagra) works by relaxing blood vessels in the penis, which increases blood flow when you are sexually aroused. The tablet does not create an erection on its own — sexual stimulation is still required. Most men take one tablet 30 minutes to one hour before sexual activity, though it can work anywhere from 15 minutes to four hours after you swallow it.
The standard starting dose is 50 mg. Your doctor may adjust this up to 100 mg or down to 25 mg depending on how your body responds and whether you have other health conditions or take other medications. Take the tablet with water, with or without food, though a heavy meal can delay how quickly it works.
Key Takeaways
- Sildenafil tablets work best when taken 30 minutes to one hour before sexual activity, though timing varies by individual and can range from 15 minutes to four hours.
- Your doctor will prescribe a specific dose (usually 25 mg, 50 mg, or 100 mg), and you should never change the dose without talking to them first.
- The tablet requires sexual arousal to work — it does not produce an erection without stimulation.
- Common side effects include headache, flushing, and indigestion, and most fade within a few hours.
- Do not take sildenafil if you use nitrate medications for chest pain, as the combination can dangerously lower blood pressure.
Standard Dosing and How to Adjust It
Sildenafil comes in three standard doses: 25 mg, 50 mg, and 100 mg tablets. Your doctor will prescribe the dose that is right for you based on your age, overall health, other medications, and how well your body responds. Most men start with 50 mg.
If 50 mg works well and you have no side effects, there is no reason to increase it. If it does not produce the result you want, your doctor may increase you to 100 mg. If you experience bothersome side effects at 50 mg, your doctor may lower you to 25 mg. Never adjust your dose on your own — always talk to your doctor before changing how much you take.
You can take sildenafil as needed (before sexual activity) rather than every day. Do not take more than one dose in a 24-hour period. If you forget to take it before sexual activity, you cannot make up for it later — straightforward wait until the next time you plan to be intimate.
Timing: When to Take Your Tablet
Take your sildenafil tablet 30 minutes to one hour before you expect to have sexual activity. This is the window when most men experience the strongest effect. However, the tablet can start working as early as 15 minutes after you swallow it, and it can remain effective for up to four hours.
If you take it with a heavy or fatty meal, absorption slows down — it may take closer to two hours to feel the full effect. Taking it on an empty stomach or with a light meal speeds up absorption. Alcohol can also delay how quickly the tablet works and may reduce how well it works overall, so limit alcohol if possible.
Do not take the tablet more than once per day. If you are planning sexual activity at an unpredictable time, you can take it a few hours in advance — it will still be in your system and ready to work when you need it.
What Happens After You Take It
Within 15 to 30 minutes of taking the tablet, you may notice mild warmth or flushing in your face and neck. This is normal and usually fades. When you become sexually aroused, the medication allows blood to flow into the penis more easily, producing an erection that typically lasts as long as you remain aroused and stimulated.
The erection goes away naturally after orgasm or when sexual stimulation stops — the tablet does not force an erection to stay. Most men report that the erection is firmer and lasts longer than it would without the medication, but the experience feels natural and responsive to what is happening in the moment.
The tablet is still in your bloodstream for several hours after you take it, so you may be able to have another erection during that window if you become aroused again. There is no need to take another dose — one tablet per day is the limit.
Common Side Effects and How Long They Last
The most common side effects are headache, facial flushing (redness and warmth), and indigestion or heartburn. These occur in roughly 10 to 20 percent of men who take sildenafil and are usually mild. They typically fade within a few hours as the medication leaves your system.
Other side effects that some men report include nasal congestion, back pain, muscle aches, and blurred vision or sensitivity to light. These are less common and also tend to be temporary. Taking the tablet with food or lowering your dose may reduce side effects.
If you experience chest pain, sudden vision loss, sudden hearing loss, or an erection that lasts longer than four hours (priapism), stop sexual activity and seek medical attention right away. These are rare but serious and require when ready care.
Medications and Conditions That Interact With Sildenafil
Do not take sildenafil if you use any medication containing nitrates — these are prescribed for chest pain and angina and include nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate. The combination can cause a dangerous drop in blood pressure. Tell your doctor about all your medications before you start sildenafil.
Sildenafil can lower blood pressure, so use caution if you take blood pressure medications. Your doctor may need to adjust your dose or monitor you more closely. Certain other medications — including some antifungals, antibiotics, and HIV medications — can increase the level of sildenafil in your blood, so your doctor may recommend a lower dose.
If you have heart disease, low blood pressure, liver or kidney problems, or a history of stroke or heart attack, tell your doctor before taking sildenafil. These conditions do not necessarily mean you cannot take it, but your doctor needs to know to prescribe the right dose and monitor your safety.
Storage and Handling
Store sildenafil tablets at room temperature (68 to 77 degrees Fahrenheit) in a dry place away from moisture, heat, and light. Keep them in their original container with the label intact so you know the dose and expiration date. Do not store them in a bathroom medicine cabinet, where humidity can damage them.
Check the expiration date before you take a tablet. Do not use sildenafil after the date printed on the bottle. If you have leftover tablets you no longer need, ask your pharmacist how to dispose of them safely — do not flush them down the toilet or throw them in the trash unless the label says it is safe to do so.
Frequently Asked Questions
Can I take sildenafil every day?
Sildenafil is designed to be taken as needed before sexual activity, not every day. Taking one dose per day is the maximum. If you need help with erectile function on a regular basis, talk to your doctor — they may recommend a different treatment plan or a different medication.
What if I take it and nothing happens?
If sildenafil does not work the first time, it does not mean it will never work. Make sure you waited at least 30 minutes after taking it, that you were sexually aroused, and that you did not take it with a heavy meal or large amounts of alcohol. If it still does not work after a few tries, talk to your doctor — they may increase your dose or explore other causes.
Can I drink alcohol while taking sildenafil?
Small amounts of alcohol are generally safe, but larger amounts can reduce how well sildenafil works and increase side effects like headache and dizziness. Limit alcohol or avoid it on days you plan to take the tablet.
How long does one tablet last?
One tablet typically remains effective for three to four hours, though some men feel effects for up to six hours. The exact duration varies by dose, individual metabolism, and whether you ate before taking it. You do not need to take another dose during this window if you become aroused again.
Is sildenafil safe if I have diabetes or high blood pressure?
Many men with diabetes and high blood pressure take sildenafil safely. However, tell your doctor about these conditions before you start — they may affect which dose is right for you or require closer monitoring. Your doctor will help you decide whether it is safe in your specific situation.