The average dose of Viagra (sildenafil) is 50 mg, taken as needed about one hour before sexual activity. This is the standard starting dose for most men and the one prescribed unless there’s a specific reason to go higher or lower. From there, the dose can be adjusted up to 100 mg or down to 25 mg depending on how well it works and how your body handles it.
The Three Available Doses
Viagra comes in three tablet strengths: 25 mg, 50 mg, and 100 mg. Nearly everyone starts at 50 mg. If that provides a reliable erection without bothersome side effects, there’s no reason to change it. If 50 mg isn’t quite enough, the dose can be increased to 100 mg, which is the maximum. If 50 mg works but causes headaches, flushing, or other side effects, dropping to 25 mg often helps while still being effective.
The maximum recommended dose is 100 mg in a single day, and you should not take it more than once in 24 hours regardless of the strength.
How and When to Take It
The standard guidance is to take Viagra roughly one hour before sexual activity, but the actual timing window is flexible. It can be taken anywhere from 30 minutes to 4 hours beforehand. Most men find that taking it about an hour ahead gives the best results.
Food matters more than most people realize. A high-fat meal significantly slows absorption, which means the pill takes longer to kick in and may feel less effective. Taking it on an empty stomach, or after a light meal, gives the fastest and most reliable response.
How Long the Effects Last
Viagra is often described as lasting about four to six hours, but research suggests the window is wider than that. In a study published in European Urology, 97% of men achieved erections sufficient for intercourse at one hour after taking sildenafil, and 74% still could at the 12-hour mark. That doesn’t mean you’ll have an erection for 12 hours. It means the medication remains active in your system long enough to respond to arousal well beyond the commonly cited window.
Peak effects typically occur between 30 and 120 minutes after taking the tablet. After that, the effect gradually tapers rather than cutting off abruptly.
How Viagra Works in the Body
An erection depends on blood flow. When you’re aroused, your body releases a chemical signal that relaxes the smooth muscle in the blood vessels of the penis, allowing them to widen and fill with blood. An enzyme called PDE5 naturally breaks down that signal, which is part of why erections don’t last indefinitely.
Viagra blocks PDE5, which lets the relaxation signal build up and persist. The result is stronger blood flow to the penis and a firmer erection. Importantly, Viagra doesn’t create arousal on its own. It amplifies the body’s natural response to sexual stimulation. Without arousal, the pill won’t produce an erection.
When a Lower Dose Is Recommended
Certain medications and health conditions change how your body processes sildenafil, which can effectively make a standard dose much stronger than intended. The most notable example involves certain HIV medications: men taking ritonavir are advised to use only 25 mg, and no more than 25 mg within a 48-hour period. Ritonavir slows the breakdown of sildenafil so dramatically that blood levels can rise to 11 times what they’d normally be.
Older adults and men with liver or kidney problems also tend to process the drug more slowly, which means it stays in the bloodstream longer and at higher concentrations. Starting at 25 mg is common in these situations, with the option to increase if needed. Other blood pressure medications and certain antibiotics or antifungals can have similar interactions, so your prescriber will factor in everything you’re currently taking before choosing a dose.
Why More Isn’t Better
Some men assume that if 50 mg works, 100 mg will work even better. That’s not always the case. Higher doses increase the likelihood and intensity of side effects like headaches, nasal congestion, facial flushing, and visual changes (a blue-green tint to vision is a known effect at higher doses). For many men, 50 mg produces a full therapeutic response, and doubling it just adds side effects without meaningful improvement.
Going above 100 mg is not recommended under any circumstances. The drug was tested extensively at these three dose levels, and 100 mg represents the ceiling where the benefit-to-risk balance still holds. Taking more does not produce proportionally better results but does increase the chance of a dangerous drop in blood pressure or prolonged erection requiring emergency treatment.