Viagra dosage for erectile dysfunction (ED) is usually 50 mg, taken about 1 hour before sex and no more than once a day. Depending on how well it works and how well you tolerate it, a doctor can lower the dose to 25 mg or raise it to the 100 mg maximum. Older men, men with liver or severe kidney problems and men on certain medicines often start at 25 mg. Viagra is one of several options in modern erectile dysfunction treatment.
Sources: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information; EAU Guidelines — Sexual and Reproductive Health — Management of Erectile Dysfunction
- Viagra (sildenafil) tablets come in 25 mg, 50 mg and 100 mg. The FDA label recommends 50 mg for most men, taken as needed about 1 hour before sex.
- The maximum Viagra dosage is 100 mg, and you should take no more than one dose a day. Taking more does not help and raises the risk of side effects.
- A 25 mg starting dose is advised for men over 65, men with liver impairment or severe kidney impairment, and men on alpha-blockers, ritonavir or strong CYP3A4 inhibitors.
- In the label’s trials, 63%, 74% and 82% of men on 25, 50 and 100 mg reported better erections, compared with 24% on placebo.
- Many apparent “failures” come from wrong use: too low a dose, a heavy meal, bad timing or no sexual stimulation.
- Viagra dosage at a glance: 25, 50 and 100 mg
- How to take your Viagra dose: timing, food and frequency
- Does a higher Viagra dosage work better?
- Who should start on a 25 mg Viagra dosage
- How a doctor adjusts your Viagra dosage
- Maximum Viagra dosage and taking too much
- Viagra dosage vs sildenafil for pulmonary hypertension
- Who should not take Viagra at any dose
- When to see a doctor
- FAQs about Viagra dosage
Viagra dosage at a glance: 25, 50 and 100 mg
Viagra is the brand name for sildenafil citrate, a phosphodiesterase type 5 (PDE5) inhibitor approved by the FDA to treat erectile dysfunction. Brand-name Viagra is a blue, rounded, diamond-shaped film-coated tablet. It comes in three strengths, stamped “VGR 25”, “VGR 50” or “VGR 100” on one side. Generic sildenafil tablets for ED come in the same strengths but may look different.
The Viagra dosage is not chosen by body weight. The label sets one usual starting point, 50 mg, and allows it to move up or down according to two things: how well it works for you and which side effects you get. The table below sums up the dosing rules in the FDA prescribing information.
| Situation | Viagra dose | Notes from the FDA label |
|---|---|---|
| Most men with ED | 50 mg | Taken as needed, about 1 hour before sex (range 30 minutes to 4 hours) |
| Not enough effect, well tolerated | Up to 100 mg | 100 mg is the maximum recommended dose |
| Bothersome side effects at 50 mg | 25 mg | Lowest tablet strength |
| Age over 65, liver impairment, severe kidney impairment | Consider starting at 25 mg | The body clears sildenafil more slowly |
| Taking an alpha-blocker | Start at 25 mg | Be stable on the alpha-blocker first |
| Taking ritonavir | 25 mg | No more than 25 mg in 48 hours |
| Strong CYP3A4 inhibitors or erythromycin | Consider starting at 25 mg | For example ketoconazole, itraconazole, saquinavir |
| Any situation | Once a day at most | Maximum recommended dosing frequency |
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
How to take your Viagra dose: timing, food and frequency
Viagra is an “as needed” medicine, not a daily one, and the Viagra dosage is taken only before sex. The FDA label says to take it about 1 hour before sexual activity, although it can be taken anywhere from 30 minutes to 4 hours beforehand. MedlinePlus gives the same advice and adds that sildenafil usually should not be taken more than once every 24 hours.
You can take Viagra with or without food. A heavy, high-fat meal, however, slows absorption of any Viagra dosage: in the label’s studies the time to peak blood level was delayed by about 60 minutes on average, and the peak level was about 29% lower. The NHS notes that a large meal may delay the erection and advises avoiding grapefruit juice and too much alcohol.
Sources: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information; NHS — How and when to take sildenafil; MedlinePlus — Sildenafil
Viagra does not cause an erection by itself. It strengthens the natural response to sexual stimulation, so you still need arousal and touch for it to work. The exact onset, peak and how long the effect lasts are covered in detail in our guide on how long Viagra lasts, so we only summarize them here.
Source: EAU Guidelines — Sexual and Reproductive Health — Management of Erectile Dysfunction
Does a higher Viagra dosage work better?
On average, yes, up to a point. In the Viagra dosage trials summarized in the FDA label, 63% of men on 25 mg, 74% on 50 mg and 82% on 100 mg reported better erections, compared with 24% on placebo. The label also notes that erection scores improved more at 50 mg and 100 mg than at 25 mg. The European Association of Urology (EAU) guideline cites similar figures: 56%, 77% and 84% of general ED patients on 25, 50 and 100 mg reported improved erections.
Sources: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information; EAU Guidelines — Sexual and Reproductive Health — Management of Erectile Dysfunction
The pivotal 1998 study in the New England Journal of Medicine showed the same pattern. In a 24-week trial of 532 men, erectile function rose as the dose increased. In a second, flexible-dose study of 329 men, doses could be raised to 100 mg based on effect and tolerance. During the last four weeks, 69% of attempts at intercourse succeeded on sildenafil, compared with 22% on placebo.
The trade-off: more side effects at higher doses
A higher Viagra dosage also brings more side effects. In the label’s fixed-dose studies, headache was reported by 16% of men on 25 mg, 21% on 50 mg and 28% on 100 mg (7% on placebo). Abnormal vision, such as a blue tinge or light sensitivity, rose from 1% at 25 mg and 2% at 50 mg to 11% at 100 mg. That is why the best dose is the lowest one that reliably works for you, not automatically the strongest. For the full list of reactions and the rare serious ones, see our article on sildenafil side effects.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
Who should start on a 25 mg Viagra dosage
Some men build up higher sildenafil levels in their blood from the same tablet. For them, the FDA label recommends starting with a low Viagra dosage, 25 mg, and increasing only if needed.
Men over 65
Healthy volunteers aged 65 or older cleared sildenafil more slowly, with blood exposure (AUC) about 84% to 107% higher than in younger men. A 25 mg starting Viagra dosage lets a doctor see how you respond before moving up.
Liver and kidney problems
A 25 mg starting dose should be considered in men with liver impairment such as cirrhosis. Mild and moderate kidney impairment did not change sildenafil levels after a single 50 mg dose. In severe kidney impairment (creatinine clearance below 30 mL/min), however, peak levels and total exposure roughly doubled, so the label also suggests a 25 mg Viagra dosage for this group.
Men taking alpha-blockers
Alpha-blockers such as doxazosin are used for high blood pressure or an enlarged prostate, and they also lower blood pressure. The label says you should be stable on your alpha-blocker before starting Viagra and that Viagra should begin at 25 mg, to limit the risk of dizziness or fainting from low blood pressure.
Men taking ritonavir or strong CYP3A4 inhibitors
Some medicines block CYP3A4, the liver enzyme that breaks down sildenafil. With ritonavir, an HIV medicine, the recommended Viagra dosage is 25 mg, and no more than 25 mg in 48 hours. With strong CYP3A4 inhibitors such as ketoconazole, itraconazole or saquinavir, or with the antibiotic erythromycin, a 25 mg starting dose should be considered.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
How a doctor adjusts your Viagra dosage
The EAU guideline recommends starting sildenafil at 50 mg and adapting the dose to each man’s response and side effects. In practice, a doctor reviews how the first few attempts on your Viagra dosage went. If erections were not firm enough and side effects were mild, the dose can go up to 100 mg. If headache, flushing or a stuffy nose were bothersome and erections were good, the dose can come down to 25 mg.
Sources: EAU Guidelines — Sexual and Reproductive Health — Management of Erectile Dysfunction; MedlinePlus — Sildenafil
Before you decide Viagra “doesn’t work”
Many men who think sildenafil has failed have never used it correctly. In a study of 100 men referred as non-responders, 56 had used it inappropriately. Forty-five had never tried the highest recommended dose of 100 mg, 32 had taken the pill on a full stomach right after a meal, 22 had taken it just before sex, and 12 did not know that sexual stimulation is needed. After proper dose titration and timing advice, 31 of the 100 men responded, 10 on 50 mg and 21 on 100 mg.
A second study looked at 253 non-responders referred from primary care. After 17 were excluded because of contraindications, simple re-education (a short video, personal instruction and written sheets) turned 41.5% of the rest into responders. Incorrect use explained 81% of the failures. The EAU guideline likewise states that patient education can salvage an apparent non-responder and that men may wait too short or too long after taking the pill.
Sources: J Urol (PubMed) — Salvage of sildenafil failures referred from primary care physicians (Atiemo et al., 2003); EAU Guidelines — Sexual and Reproductive Health — Management of Erectile Dysfunction
If the tablet still does not work at the right Viagra dosage and timing, other options include a different PDE5 inhibitor, penile injections or, for severe ED, a penile implant. Some men also prefer a long-acting alternative such as a tadalafil daily dose.
Maximum Viagra dosage and taking too much
The maximum recommended Viagra dosage is 100 mg, and the maximum dosing frequency is once a day. Taking two tablets, or a second dose later the same day, is not recommended. In studies of healthy volunteers given single doses up to 800 mg, side effects were similar to those at lower doses but more frequent and more severe.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
MedlinePlus advises taking sildenafil exactly as prescribed, never more or more often. Sildenafil is also sold under other brand names, such as Revatio and Liqrev, for lung conditions, and you should use only one sildenafil product at a time. The FDA label adds that combining Viagra with Revatio or with other PDE5 inhibitors such as tadalafil has not been studied and is not recommended.
Sources: MedlinePlus — Sildenafil; DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
If you think you have taken too much, the NHS advises calling NHS 111, or 999 for an ambulance in an emergency, and not driving yourself to hospital. In the US, MedlinePlus lists the poison control helpline (1-800-222-1222) and 911 for collapse, seizures or trouble breathing. Wherever you are, contact your local emergency services and take the medicine packet with you.
Sources: NHS — How and when to take sildenafil; MedlinePlus — Sildenafil
Pills bought online without a prescription
Doses printed on unlicensed products cannot be trusted. The FDA warns that many products sold for sexual enhancement are likely to contain hidden drug ingredients, so you may not know what dose, or what drug, you are actually taking. This risk is one more reason to get sildenafil through a doctor and a licensed pharmacy.
Source: FDA — Sexual Enhancement and Energy Product Notifications
Viagra dosage vs sildenafil for pulmonary hypertension
The same active ingredient is used at a different dose for a different disease, so the Viagra dosage does not apply to it. Revatio contains sildenafil and is approved for pulmonary arterial hypertension (PAH), high blood pressure in the arteries of the lungs. It is a scheduled, regular treatment rather than an as-needed tablet. Do not swap one for the other without a doctor’s advice.
| Feature | Viagra (ED) | Revatio (PAH) |
|---|---|---|
| Tablet strengths | 25, 50, 100 mg | 20 mg |
| Usual adult dose | 50 mg as needed | 20 mg three times a day |
| How often | At most once a day | Every day, at regular times |
| Tablet look | Blue, rounded diamond shape | White to off-white, round |
Sources: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information; DailyMed (FDA label) — REVATIO (sildenafil) prescribing information
Who should not take Viagra at any dose
No Viagra dosage is safe for some men. The FDA label lists three contraindications:
- Nitrates and nitric oxide donors, such as nitroglycerin for chest pain, used regularly or now and then. The label also includes organic nitrites in any form, such as amyl nitrite “poppers”. The combination can cause a dangerous drop in blood pressure.
- Guanylate cyclase stimulators such as riociguat, used for some forms of pulmonary hypertension.
- Known allergy to sildenafil.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
Men with heart disease need a check before starting, because the label notes a potential cardiac risk of sexual activity in men with existing cardiovascular disease. Our article on erectile dysfunction and heart disease explains why ED can be an early warning sign. Viagra is not indicated for women or for children.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
When to see a doctor
Talk to a doctor before you start Viagra or change your dose, especially if you are over 65, have liver or kidney disease, or take medicines for blood pressure, the prostate, HIV or fungal infections. Ask for a review if 50 mg is not working after several correct attempts, or if side effects are hard to tolerate. These are reasons to seek urgent medical help:
- An erection that lasts more than 4 hours, painful or not (priapism), which can permanently damage the penis.
- Sudden loss or decrease of vision in one or both eyes.
- Sudden loss or decrease of hearing, sometimes with ringing or dizziness.
- Chest pain, fainting or severe dizziness during or after sex.
- Taking more than the prescribed dose, or taking Viagra after using a nitrate.
Sources: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information; MedlinePlus — Sildenafil
If you want a personal answer about the right Viagra dosage, you can arrange a free, confidential consultation with our urologist-andrologist on WhatsApp. We review your health and medicines and, if tablets are not enough, discuss every erectile dysfunction treatment option.
FAQs about Viagra dosage
What is the normal Viagra dosage?
The normal starting Viagra dosage for most men is 50 mg, taken about 1 hour before sex. Depending on results and side effects, the dose can be increased to 100 mg or decreased to 25 mg. You should not take more than one dose in a day. Your doctor may start lower if you are older or take certain medicines.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
Is 100 mg of Viagra too much?
No, 100 mg is the maximum recommended Viagra dosage, and it is appropriate for men who tolerate sildenafil but need a stronger effect. It does carry more side effects: in fixed-dose trials, headache and vision changes were more common at 100 mg than at 25 or 50 mg. Men over 65 or on interacting medicines usually start lower.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
Is 25 mg of Viagra enough?
For some men, yes. In the label’s trials, 63% of men on 25 mg reported improved erections, compared with 24% on placebo, although 50 and 100 mg worked better on average. A 25 mg Viagra dosage is often chosen for older men, men with liver or severe kidney problems, and men taking alpha-blockers or ritonavir.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
Can I take two 50 mg Viagra tablets?
Only if your doctor has prescribed a 100 mg Viagra dosage and told you to take it this way. Never take extra tablets on your own, and never take more than one dose a day. Raising the dose above 100 mg does not add benefit, and higher doses increase how often and how severely side effects occur.
Sources: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information; MedlinePlus — Sildenafil
Should I take Viagra on an empty stomach?
You can take Viagra with or without food, but a heavy, high-fat meal delays its peak level by about an hour and lowers it by about 29%. If it seems to work slowly, try taking it on a lighter stomach. In one study of non-responders, 32 of 100 men had taken it right after a full meal.
Sources: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information; Eur Urol (PubMed) — Sildenafil failures may be due to inadequate patient instructions and follow-up (Hatzichristou et al., 2005)
Does the Viagra dosage change with age?
Yes, it can. Men aged 65 and older clear sildenafil more slowly, and their blood levels were about 84% to 107% higher in studies. The FDA label therefore suggests considering a 25 mg starting dose in men over 65. The dose can then be increased if erections are not good enough and side effects are acceptable.
Source: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information
Can I take Viagra every day?
Viagra is approved for use as needed, with a maximum Viagra dosage of one tablet per day. It is not designed as a scheduled daily treatment for ED. Men who want a daily option usually discuss low-dose tadalafil with their doctor. Sildenafil is taken three times a day only for pulmonary hypertension, as Revatio, under specialist care.
Sources: DailyMed (FDA label) — VIAGRA (sildenafil citrate) prescribing information; DailyMed (FDA label) — REVATIO (sildenafil) prescribing information
What should I do if 100 mg of Viagra doesn’t work?
First check how you are taking it: wait about an hour, avoid a heavy meal and make sure there is sexual stimulation. Studies show many non-responders improve after correct instructions. If it still fails after several attempts, see a doctor to look for the cause of ED and discuss other treatments.
Sources: J Urol (PubMed) — Salvage of sildenafil failures referred from primary care physicians (Atiemo et al., 2003); EAU Guidelines — Sexual and Reproductive Health — Management of Erectile Dysfunction
Medically reviewed by Assoc. Prof. Dr. Zülfü Sertkaya, urologist and andrologist (FEBU), Istanbul. Last reviewed: October 2026.
This article is for general information and does not replace an individual consultation with a qualified doctor.
- DailyMed (FDA label) — VIAGRA (sildenafil citrate) tablets — prescribing information
- DailyMed (FDA label) — REVATIO (sildenafil) — prescribing information
- EAU Guidelines — Sexual and Reproductive Health — Management of Erectile Dysfunction
- NHS — How and when to take sildenafil
- MedlinePlus — Sildenafil
- N Engl J Med (PubMed) — Oral sildenafil in the treatment of erectile dysfunction (Goldstein et al., 1998)
- Eur Urol (PubMed) — Sildenafil failures may be due to inadequate patient instructions and follow-up (Hatzichristou et al., 2005)
- J Urol (PubMed) — Salvage of sildenafil failures referred from primary care physicians (Atiemo et al., 2003)
- FDA — Sexual Enhancement and Energy Product Notifications
