The maximum recommended dose of sildenafil for erectile dysfunction is 100 mg, taken no more than once per day. For pulmonary hypertension, the maximum is 20 mg three times daily. These limits exist because higher doses don’t improve effectiveness but do increase the risk of side effects.
Maximum Dose for Erectile Dysfunction
Sildenafil for ED (sold as Viagra and generics) comes in 25 mg, 50 mg, and 100 mg tablets. Most people start at 50 mg, taken roughly an hour before sexual activity. From there, the dose can be adjusted up to 100 mg or down to 25 mg based on how well it works and how well you tolerate it. The 100 mg ceiling is a hard limit: clinical trials showed no additional benefit beyond that dose, only more side effects.
You should not take more than one dose in a 24-hour period, regardless of the strength.
Maximum Dose for Pulmonary Hypertension
When sildenafil is prescribed for pulmonary arterial hypertension (sold as Revatio), the dosing schedule is completely different. The recommended dose is 20 mg taken three times a day, spaced 4 to 6 hours apart. That works out to a total daily maximum of 60 mg. Clinical trials found that going higher than 20 mg three times daily did not produce greater benefit, so doses above that are not recommended.
Lower Maximums for Some People
Several groups of people end up with significantly higher levels of the drug in their bloodstream from the same dose, which means their effective maximum is lower even though the absolute cap remains 100 mg.
Adults over 65: The body clears sildenafil more slowly with age. In studies, healthy volunteers aged 65 and older had roughly 84% higher blood levels of the drug compared to younger adults taking the same dose. The recommended starting dose for this group is 25 mg.
Liver impairment: Conditions like cirrhosis reduce the liver’s ability to break down sildenafil, leading to higher and longer-lasting blood levels. A 25 mg starting dose is recommended here as well.
Severe kidney impairment: People with significantly reduced kidney function also clear the drug more slowly. A 25 mg starting dose is recommended, though based on how well it works and is tolerated, the dose can still be increased stepwise to 50 mg or up to 100 mg. People with mild to moderate kidney impairment don’t need a dose adjustment.
In all three groups, the higher drug levels aren’t just a technicality. They translate directly into a greater chance of side effects like headache, flushing, visual changes, and drops in blood pressure.
Why the 100 mg Limit Matters
Sildenafil works by relaxing blood vessels, which is why it helps with both erections and lung blood pressure. But that same mechanism affects blood vessels throughout the body. At higher doses, the blood pressure drop becomes more pronounced, and certain risks increase.
Blood Pressure and Nitrate Interactions
The most dangerous interaction is with nitrate medications, commonly prescribed for chest pain. Sildenafil amplifies the blood-pressure-lowering effect of nitrates dramatically. In one study, combining the two produced a four-fold greater drop in systolic blood pressure compared to taking a nitrate alone. This can cause dangerously low blood pressure, fainting, or worse. Taking sildenafil in any form is contraindicated if you use nitrates, whether regularly or occasionally.
Vision Risks
Sildenafil has been linked to a rare but serious eye condition called nonarteritic anterior ischemic optic neuropathy (NAION), which involves sudden vision loss in one eye due to reduced blood flow to the optic nerve. In a case series from the American Academy of Ophthalmology, 10 patients who used sildenafil at least two to three times per week developed NAION in one eye, then continued using the medication and went on to develop it in the other eye as well. The current consensus is that anyone who experiences vision loss in one eye while using sildenafil should stop taking it, because the risk of the same thing happening to the other eye is elevated.
Priapism
Sildenafil can, in rare cases, cause an erection lasting four hours or more. This is a medical emergency because prolonged erection can permanently damage tissue. The risk increases with higher blood levels of the drug, which is one reason the dose ceiling exists and why certain populations are started at 25 mg.
What Happens if You Take More Than 100 mg
Taking more than the recommended maximum doesn’t make the medication work better. What it does is increase the severity and likelihood of side effects: more intense headaches, significant drops in blood pressure, visual disturbances (including a blue tint to vision), nasal congestion, and dizziness. At very high doses, the risk of the serious complications described above climbs as well. If you’ve taken more than 100 mg and are experiencing symptoms like chest pain, vision changes, or an erection that won’t subside, that warrants emergency medical attention.