Sildenafil (Viagra) Dosage: 25mg, 50mg or 100mg, and How Much to Take

Short answer: Sildenafil (Viagra) is usually started at 50mg, and the UK product information (Viagra SmPC, section 4.2) says the dose can then be lowered to 25mg or raised to 100mg depending on how well it works and any side effects, with 100mg the maximum. Take it about 1 hour before sex (anywhere from 30 minutes to 2 hours before). Never take more than one tablet in 24 hours. A GPhC-registered pharmacist reviews every consultation and decides the dose: a first order starts at 50mg, or at 25mg if you take an alpha-blocker, have a liver problem or take one of a few medicines that raise sildenafil levels, and when you reorder the dose can go up one strength if the last one did not work well enough and caused no side effects. Viagra Connect, supplied after a pharmacist consultation, comes in one strength, 50mg.

This guide sets out what the UK product information for Viagra and for generic sildenafil, the Viagra leaflet and the NHS say about the dose, as of October 2026, and how our consultation follows them: the strengths, the first dose, when 25mg and 100mg are used, how often, how much is too much, weight, older men, how much we can supply and the prices, and Viagra Connect. The pharmacist decides whether sildenafil and a dose are right for you.

What is the usual sildenafil dose, and which strengths are there?

The usual dose of sildenafil is 50mg, and it comes as 25mg, 50mg and 100mg tablets. The UK product information says the recommended dose is 50mg taken as needed about an hour before sex, that the dose can be raised to 100mg or lowered to 25mg depending on how well it works and how well you tolerate it, that 100mg is the maximum, and that it should be taken no more than once a day (Viagra SmPC 4.2).

The sildenafil we supply is a generic version. Generic sildenafil tablets contain the same active ingredient at the same strength and are licensed in the UK. The product information for a generic sildenafil (Amarox, emc 13550, revised August 2026) gives the same dose rules as Viagra's. We supply all three strengths, and the pharmacist decides which suits you.

How much Viagra should I take the first time?

Usually 50mg: it is the recommended starting dose in the Viagra leaflet, and the usual starting dose in our consultation unless your answers call for 25mg (see the next section). Take it about 1 hour before sex (anywhere from 30 minutes to 2 hours before). It takes about an hour to work. A heavy or high-fat meal can delay how quickly it works.

These tablets only work with sexual stimulation. Swallow the tablet whole with water, the leaflet says. The time it takes to work varies from person to person, so do not take a second tablet the same day if the first does not seem to work. This is how our consultation sets your dose and changes it:

If the effect feels too strong or too weak, the leaflet says to talk to your doctor or pharmacist: tell us, so the pharmacist can look at your dose before your next order.

When is 25mg of sildenafil used, and is it enough?

25mg is used as a lower starting dose when your body may clear sildenafil more slowly, or when low blood pressure is more likely, and as a dose to step down to if 50mg causes side effects; whether it is enough depends on the man. The UK product information suggests starting at 25mg if you take an alpha-blocker, once you are settled on it, if you have a liver problem or severe kidney problems, or if you take a medicine that slows how your body clears sildenafil, known as a CYP3A4 inhibitor, such as the antibiotic erythromycin (Viagra SmPC 4.2 and 4.5). With an alpha-blocker, a few men get dizzy from low blood pressure, most often within 4 hours of the tablet (SmPC 4.4).

Our consultation asks three questions that decide this. A yes to any one of them means sildenafil starts at 25mg:

• Do you take an alpha-blocker (tamsulosin, alfuzosin, doxazosin, terazosin, prazosin, silodosin or indoramin)? These are often used for prostate symptoms or blood pressure.
• Do you have any liver disease or reduced liver function?
• Do you take erythromycin, aprepitant, diltiazem, fluconazole or verapamil?

If you take an alpha-blocker, it also asks: "Has your alpha-blocker dose stayed the same recently, without dizziness or fainting?" We can only supply erectile dysfunction treatment once your alpha-blocker dose has stayed the same, without dizziness or fainting.

Some medicines of this kind have a stronger effect: the product information expects ketoconazole and itraconazole to raise sildenafil levels more, and advises against taking sildenafil with ritonavir, an HIV medicine (SmPC 4.2 and 4.5). Our consultation does not supply sildenafil to anyone taking any of these:

• An HIV protease inhibitor (atazanavir, darunavir, ritonavir, fosamprenavir, lopinavir, saquinavir or tipranavir)
• Ketoconazole, itraconazole, voriconazole or clarithromycin

We also do not supply it to anyone with severe liver impairment, which its product information rules out too (SmPC 4.3), or with severe kidney failure (an eGFR under 30) or on dialysis, although its product information gives a 25mg dose for severe kidney problems.

25mg is also where the dose can go if 50mg gives you side effects: the product information says the dose can be lowered depending on how well you tolerate it (SmPC 4.2), and when you reorder you can choose the same dose or, where there is one, a lower strength. If 25mg does not work well enough and causes no side effects, the pharmacist can consider 50mg at your next order.

Is it OK to take 100mg of sildenafil?

Yes, if it is the dose agreed for you by your pharmacist or doctor: 100mg is the maximum dose in the UK product information, which says the dose can be raised from 50mg to 100mg depending on how well it works and how well you tolerate it (Viagra SmPC 4.2). Even at 100mg, never take more than one tablet in 24 hours. The Viagra leaflet says doses above 100mg do not work any better, and taking more than you should can bring more side effects, and more severe ones.

In our consultation, 100mg is reached step by step. When you reorder, we ask how your last tablets worked and whether you had any side effects. If your dose did not work well enough and caused no side effects, the pharmacist can consider the next strength up. That means one strength at a time: from 25mg to 50mg, or from 50mg to 100mg. If you take an alpha-blocker, a step up is flagged for the pharmacist to confirm before supply. Either way, the pharmacist checks your answers before anything is sent.

The exception: if you have already taken a higher dose from your GP or another pharmacy, and it worked for you without side effects, you can ask for it in your consultation. Our pharmacist will check this with you. This does not apply if you take an alpha-blocker.

If a medicine has not worked after 4 to 8 tries at the highest dose that suits you, your pharmacist may suggest trying a different one. For what to do next, see Viagra not working; for the other tablets, see sildenafil vs tadalafil and tadalafil dosage.

How many Viagra can you take in a day, and can you take 50mg twice?

One, so you cannot take 50mg twice in a day. Never take more than one tablet in 24 hours. The UK product information's limit is once a day (Viagra SmPC 4.2), and the Viagra leaflet and the NHS say the same. That holds even if the first tablet did not seem to work.

Do not take two 50mg tablets together to make a stronger dose either. If 50mg is not working well enough, tell us: if it caused no side effects, the pharmacist can consider 100mg when you reorder, and you would then take one 100mg tablet, still no more than once in 24 hours.

Do not take sildenafil with any other medicine that contains it, including Viagra Connect, or with another erectile dysfunction treatment. Do not use unlicensed herbal remedies for erections, and do not stop any prescribed medicine unless your doctor tells you to. For timing and food, see how long sildenafil lasts, and for alcohol, Viagra and alcohol.

How much sildenafil is too much?

More than 100mg in 24 hours is too much. 100mg is the maximum dose (Viagra SmPC 4.2), and in single-dose studies in volunteers, doses above it did not work any better but caused the same side effects as lower doses, more often and more severely, among them headache, flushing, dizziness, indigestion, a blocked nose and changes to vision (SmPC 4.9; Viagra leaflet section 3).

If you have taken more sildenafil than your prescription, packet or leaflet says, the NHS says to call NHS 111. If you are told to go to A and E, do not drive yourself: ask someone to drive you or call 999 for an ambulance, and take the sildenafil packet or its leaflet with you, with any tablets left and any other medicines you take. Get help straight away for either of these:

• Prolonged erection. Seek emergency treatment for an erection lasting longer than 4 hours. This is a medical emergency.
• Cardiovascular symptoms. Stop and call 999 if you get chest pain, dizziness or fainting during or after sexual activity. Do not take another dose.

For urgent medical concerns, call NHS 111 or 999. For every side effect and how often each one happens, see Viagra side effects.

Is Viagra dosage based on your weight?

No. The UK product information sets the dose of sildenafil by how well it works and how well you tolerate it, not by body weight: section 4.2 gives no dose by weight, and the men it doses differently are those taking an alpha-blocker or certain other medicines and those with liver or severe kidney problems, while men aged 65 or over need no change (Viagra SmPC 4.2). So weight alone is not a reason for a heavier man to take 100mg, or for a lighter man to take 25mg. The usual start is 50mg whatever you weigh.

Our consultation does not ask your weight. Weight comes into the safety checks instead: obesity is one of the risk factors for heart disease it asks about, and with three or more of them we cannot supply treatment, and ask you to see your GP so your heart health can be assessed. Losing weight, stopping smoking, drinking less alcohol and exercising can all help. If you cycle more than 3 hours a week, try a break from cycling.

What is the right Viagra dosage for a 60 or 70 year old?

The same as for a younger man: the usual start is 50mg, because age alone does not change the dose. The UK product information says: "Dose adjustments are not required in elderly patients (≥ 65 years old)." (Viagra SmPC 4.2). The product information for generic sildenafil says the same.

Healthy men aged 65 or over do clear sildenafil more slowly, so it reaches higher levels in their blood than in younger men (SmPC 5.2), but the product information does not ask for a lower dose for age alone. What can lower the starting dose at any age is an alpha-blocker, a liver problem or one of the medicines above, and the checks on your heart, blood pressure and other medicines apply at every age. At 60, the usual adult dose applies; the product information's note on older men starts at 65.

Our consultation for prescription sildenafil is for men aged 18 and over, with no upper age limit, and a GPhC-registered pharmacist decides the dose. We supply Viagra Connect to men aged 18 to 64.

How much sildenafil can you get, and what does it cost?

We supply 4 or 8 sildenafil tablets an order, at 25mg, 50mg or 100mg. There is a limit on how much we can supply: maximum 8 tablets per 2 weeks. Our prices are:

Viagra Connect 50mg: 2 tablets £11.99, 4 tablets £22.99, 8 tablets £34.99. Delivery is free. The consultation is free. Supplied only if your pharmacist decides it is suitable for you.

Your order comes in plain packaging, with no medicine names on it. Is the packaging discreet?

What dose is Viagra Connect?

Viagra Connect comes in one strength, 50mg: take one tablet about 1 hour before sex, and no more than one tablet a day (Viagra Connect SmPC 4.2 and leaflet section 3). Its product information allows the dose to go down to 25mg or up to 100mg for prescription sildenafil, not for Viagra Connect, so a man who needs 25mg or 100mg needs prescription sildenafil.

It also says that men who take an alpha-blocker or a medicine that raises sildenafil levels, or who have liver problems or severe kidney problems, should speak to a doctor before taking Viagra Connect, because a 25mg tablet may suit them better (Viagra Connect SmPC 4.2). Erection problems can be an early sign of heart disease, diabetes or high blood pressure. If you use Viagra Connect, book a check-up with your GP as soon as you can, within 6 months of starting it.

We supply Viagra Connect after a pharmacist consultation, to men aged 18 to 64, in one pack of 2, 4 or 8 tablets an order. Less common side effects are listed in the leaflet in your pack. Please read it before your first dose. For what else differs, see Viagra Connect vs prescription sildenafil, or all our erectile dysfunction treatments.