Sildenafil Dosage: How Much Should You Take?

Brenda Ikeji

Medically reviewed by

Dr Brenda Ikeji

Last reviewed: 26 Mar 2025

Sildenafil is a prescription drug used to treat erectile dysfunction (ED) and pulmonary hypertension. When it’s used to treat ED, there are 3 sildenafil dosages available: 25, 50, and 100mg. It affects people in different ways, so your doctor will prescribe a higher or lower dosage of sildenafil depending on your situation.


In this guide, you’ll learn more about sildenafil dosage for ED, the reasons your doctor might prescribe different amounts, what to do if your dosage is not working, and other common issues.

Contents
Pack of Sildenafil 50mg dosage
 

What is sildenafil?

Sildenafil is a drug that belongs to a group of medicines called phosphodiesterase-5 (PDE-5) inhibitors. PDE-5 inhibitors work to improve blood flow to the penis by relaxing the blood vessels, helping blood to flow to the penis, and making it easier to get and maintain an erection.

Sildenafil is available both as a generic medication and under the brand name Viagra.

For sildenafil to work, you need to be aroused, and it may take a few attempts for it to work for you. This does not mean your sildenafil dosage is wrong. Other factors, such as having a heavy meal before taking the medication, could also stop it from working effectively. But if you have followed the instructions and it’s still not working after 8 attempts, speak with your doctor about getting a higher dose.

You may be prescribed a lower or higher dose if you have side effects or are not getting the benefits you want from the medication. You can also switch to another ED medication that works similarly to sildenafil.

You need a prescription to buy sildenafil. You can obtain a prescription by requesting sildenafil with ZAVA, all you need to do is fill in a brief online health questionnaire and one of our doctors will check to see if sildenafil is right for you.

Start an online consultation now to see if sildenafil is right for you
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What sildenafil dosages are available?

Sildenafil is available in 25, 50, and 100mg doses (the same doses as the original Viagra).

For most people, the typical starting sildenafil dose for erectile dysfunction is 50mg. This dose is prescribed to see how your body reacts to the medication and if you get any negative side effects. From here, your doctor can adjust your dose up or down as required.

The following table provides an overview of sildenafil dosage for erectile dysfunction:

Strength Dosage type (maximum of 1 dose per 24 hours)

25mg

Minimum

50mg

Standard

100mg

Maximum

You should always take sildenafil as instructed by your doctor or pharmacist for the best results, and you must never adjust your dose without medical guidance.

If you have been prescribed sildenafil for pulmonary hypertension, the dosage and frequency you take will be different than for people with ED. Refer to your prescription or ask your doctor if you are unsure.

Standard ED sildenafil dose: 50mg

The usual starting dose for sildenafil is 50mg.

Research has found that this is an effective amount for the majority of users. For example, in one study trialling over 500 men, 77% reported improved erections when taking 50mg doses.

Another study found that 71% of men got an erection within half an hour of taking 50mg of sildenafil, and 82% did within 45 minutes.

That being said, your doctor will decide your starting dose based on your health, age, and what they think is most suitable for you. If you start taking 50mg tablets and find that you’re unable to get a long-lasting erection, your doctor might need to increase your dose.

On the other hand, if you have persistent side effects, such as dizziness, your doctor may want to lower your sildenafil dose or try a different medication. In either situation, your doctor will be able to give you advice on what to do. You should not change your own dosage of sildenafil unless your doctor has instructed you to.

Maximum sildenafil dosage: 100mg

The highest dose of sildenafil available is 100mg. Your doctor may recommend it if the 50mg dose has little or no effect. 84% of men treated with a sildenafil dosage of 100mg found it gave them an erection hard enough to have sex.

If you still find that 100mg does not work for you, try the following:

  • try using it a few more times – we recommend trying sildenafil on up to 8 separate occasions before looking for alternatives (never taking more than 1 dose per day)
  • speak to your doctor about switching to another erectile dysfunction medication
  • a non medication option alongside your treatment, such as a penis pump

Lowest sildenafil dose for erectile dysfunction: 25mg

The lowest dose of sildenafil for ED is 25mg. Taking a lower dose is less effective than high doses but that does not mean it will not work for you. Research shows that it can still help over 50% of men get improved erections.

There are a couple of reasons your doctor might prescribe a lower sildenafil tablet dosage. For some men, the 50mg dose causes unwanted side effects – particularly in older men who metabolise the medication at a much slower rate than younger men. For others, certain medical conditions or existing drug prescriptions might also mean a lower sildenafil dose is preferable to reduce any interactions.

If 25mg of sildenafil is not effective and you lose your erection during sex, you may want to consider a smaller daily dose of a different erectile dysfunction medication, such as Cialis Daily.

What is the best dose of sildenafil for me?

To work out the best sildenafil dosage for you, your doctor will likely need to know about your:

  • current health
  • blood pressure
  • cholesterol levels
  • level of fitness
  • history of medical conditions, such as heart problems or diabetes
  • any previous erectile dysfunction treatments you’ve tried

Using this information, your doctor will be able to start putting together a treatment plan for you. Depending on your experience with the initial dosage of 50mg, your doctor will be able to adjust your dose amount to your needs.

Once you find a treatment that works for you, always take it as directed by your doctor.

Is 100mg sildenafil too strong?

Sildenafil’s maximum dosage is 100mg and is approved at this strength in the UK. However, higher doses of sildenafil can lead to an increased risk of side effects, so doctors typically prescribe a standard dose of 50mg to begin with.

Is sildenafil 50mg or 100mg better?

It’s not possible to say that 50mg or 100mg of sildenafil is ‘better’ than the other. Everyone responds to sildenafil treatment differently. Some people find they can get and keep an erection on 50mg, so this would be the right dose for them. Other men find that 50mg does not give them the results they want, so their doctor may increase their sildenafil dose to 100mg.

Is it safe to take 200mg of sildenafil?

No, it is not considered safe to take 200mg of sildenafil at one time as this can increase your chances of serious side effects. It’s also not likely to improve your chances of getting an erection. You should only take sildenafil as your doctor prescribes. If you feel that sildenafil is no longer working for you and you are taking the maximum 100mg dosage, you should speak to your doctor and they may advise a suitable alternative.

My current sildenafil dosage doesn’t seem strong enough. Can I get a higher dose?

If your current sildenafil dose isn’t having the desired effects, speak with your doctor. Sometimes, a stronger dose might be the right choice. We generally recommend trying sildenafil on 8 different occasions (at least 24 hours apart) before moving to a higher dose. Sometimes it just takes a few tries to work. It’s also worth double checking if you’re doing anything that might reduce its effectiveness – such as eating large meals before taking the medication.

Dr Brenda Ikeji, medical editor and GP

When I’m prescribing sildenafil to a patient, there are several factors that I think about when deciding on the right sildenafil citrate dosage. These include the underlying causes of the patient’s erectile dysfunction, their age, weight and other health conditions they may have. For many men, a standard sildenafil dose of 50mg is highly effective. But it’s not fixed, and we adjust depending upon the patient’s experience and feedback.” – Dr Brenda Ikeji, Medical Editor.

How to take sildenafil to get the best results

To get the best results when taking sildenafil you should:

  • take the medicine as directed by your doctor or pharmacist
  • make sure you’re sexually aroused
  • avoid fatty foods or heavy meals before taking it
  • avoid drinking too much alcohol while taking it

There may be other factors affecting your sexual performance including:

  • stress
  • tiredness
  • emotional factors
  • lack of sleep

Speak to your doctor if you notice anything different about your health, start any new medications, or if you want an alternative. They will be able to work with you to find the best medication for your situation.

I have taken too much sildenafil. What should I do?

If you take more than the maximum dose of sildenafil in 24 hours (100mg), you should speak to a doctor or pharmacist.

Taking too much sildenafil can cause serious side effects and may mean you need to seek medical assistance.

Call 999 or go to A&E if:

  • you experience chest pain
  • you have a seizure or ‘fit’
  • you have a painful erection that lasts more than 2 hours

Call 111 if:

  • you experience a sudden loss or decrease in vision

Do other erectile dysfunction medications have a higher dosage than sildenafil?

Other erectile dysfunction medications are available in different doses. But a higher dose of one medication does not mean it’s better or will work faster than another medication. Some medications may work better for some people than others.

Alternative medications for erectile dysfunction include:

  1. Viagra – contains the same active ingredient as sildenafil and works in the exact same way, it is just the branded version so it has a different name, price, and packaging.
  2. Spedra – the fastest-acting ED medication that usually starts to work in 15 minutes and lasts 4 hours.
  3. Levitra – tends to work in just over 30 minutes and lasts up to 12 hours.
  4. Cialis – tends to work in 15 to 30 minutes and lasts up to 36 hours.
  5. Cialis Daily – can be taken every single day, so you’re always ready for sex when you want to be without worrying about taking a pill beforehand.
  6. Vitaros cream – applied as a cream instead of taking an oral pill, it contains 3mg per gram of alprostadil and works in 5 to 15 minutes.

Non medication options include:

  • penis vacuum pump – device uses suction to achieve erections
  • therapies – such as CBT can address any emotional factors
  • pelvic floor exercises – improves the ability to maintain erections

➤ More information on alternative ED treatment options can be found on our treatment page.

If you’re currently taking sildenafil and need any guidance on side effects, or choosing an alternative that is right for you, check out our guides:

Side Effects of Sildenafil & How to Reduce Them

What are the Best Alternatives to Viagra?

You can also fill out an online questionnaire with ZAVA and find what could work best for you today.

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Medically reviewed by:
Dr Brenda Ikeji Medical Editor

Brenda studied medicine at St Georges University of London and has most recently worked in John Radcliffe Oxford University Hospitals, covering acute and general medicine.

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Last reviewed: 26 Mar 2025






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