Authored: 19/03/2023
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Sildenafil
Overview
Sildenafil is a medication used to treat erectile dysfunction (ED) in men. It helps to achieve and maintain an erection when sexually aroused. Sildenafil works by increasing blood flow to the penis.
- Works within 30-60 minutes
- Generic version of Viagra
- Best value ED treatment
- Trial from £1
Overview
Buy Sildenafil Tablets Online
You can buy Sildenafil tablets to treat erectile dysfunction online from our registered online service.
After completing an online assessment, our UK registered and trained GP's will review your assessment. If approved, a prescription will be issued which is passed on to our UK registered online pharmacy. The pharmacy team will dispense your order, and dispatch the medication to your chosen delivery address.
Summary
| What is it? | A treatment for erectile dysfunction in men |
| Dose | Take one Sildenafil tablet about one hour before sex. For optimum performance, take on an empty stomach. The effects of Sildenafil can last between 4-6 hours. 50mg is the typical starting dose. |
| How does Sildenafil work | Increases blood flow to the penis when sexually aroused. |
| Effectiveness | ~84% of men will notice a firmer and longer-lasting erection |
| Common Side effects | Nasal congestion, headaches, facial flushing, dizziness |
| Price | Starting from £3.75 |
| Strengths | Available strengths of Sildenafil tablet are
|
What Are Sildenafil Tablets?
Sildenafil tablets are a treatment for erectile dysfunction in men. They are the most widely prescribed treatment for erectile dysfunction in the UK.
Sildenafil is the generic form of the well-known drug, Viagra .
Sildenafil is significantly cheaper and is the version that is usually prescribed by the NHS. They are a popular choice of treatment for erectile dysfunction, as medically there is no difference between Sildenafil and its branded alternative.
You can also read more about Sildenafil, other ED treatments and condition information at the NHS Choices website.
Effectiveness
The effectiveness of Sildenafil is proven in clinical trials against placebo. In men who suffered from erectile dysfunction, ~80% of those who took Sildenafil managed to achieve an erection, compared to around 17% of the group who were given water pills.
You can find out more about experiences with Sildenafil, from our UK patient Sildenafil reviews.
How It Works
Sildenafil is from a class of drug called PDE inhibitors and when taken causes blood vessels to relax. Men who suffer from ED are unable to pump enough blood into the penis to achieve a hard enough erection. Sildenafil works by stimulating blood flow to the penis when a man is sexually aroused. This helps men with ED to achieve firmer and longer-lasting erections.
How to Take Sildenafil
The typical starting dose for Sildenafil is ONE 50mg tablet 30 minutes before sexual activity. Most men will find this dose effective, however, if 50mg is too strong, you may wish to half the tablet the next time you are taking the medication. If successful, a 25mg tablet may be more suitable for your next prescription .
If the 50mg does not achieve the desired result, you should try the same dose 2-3 more times, to see if you can achieve a satisfactory erection. If this is not successful, you can increase your dosage to 100mg.
If a 100mg dose is also ineffective, speak to us about the next steps. It is advised to try it at least 5 times before giving up. However, Sildenafil should not be taken more than once in 24 hours.
If you have already used a few erectile pills without success, a face to face referral may be required .
If you have not yet tried one of the other ED medications, you may find that Tadalafil or Vardenafil is effective for you.
Patients will find different drugs more effective. This does not necessarily mean one drug is more effective than another. It can be that your body responds slightly differently to a particular medication.
Sildenafil Dosage
Sildenafil is available in 3 strengths; Sildenafil 25mg, Sildenafil 50mg and Sildenafil 100mg. The strength required, will depend on the severity of your ED, and it may require a couple of trials to find the right strength for you. Below is a dosage table to describe which strength is typically used and when.
| Strength | Use |
|---|---|
| Sildenafil 25mg Tablet | Typically used for men who have found that 50mg is too strong. |
| Sildenafil 50mg Tablet | Usually, the recommended starting dosage. Most men will find this delivers the desired response, and an erection sufficient for intercourse will be achieved. |
| Sildenafil 100mg Tablet | Usually reserved for men who have not responded to the 50mg strength. You shouldn't start treatment at 100mg, as this can potentially lead to an erection that lasts too long or becomes painful. |
Side Effects
With all medication, there is always a risk of side effects occurring. Sildenafil is well tolerated, and most side effects will go away once your body is used to the treatment.
The most common side effects are
- Headaches / Dizziness
- Flushing
- Runny/stuffed nose
- Upset stomach / Nausea / Diarrhoea
- Red and/or warm skin
- Muscle pain / Back Pain
- Blurred vision
The side effects listed below are more serious, and you should stop taking Sildenafil, and report these to your doctor or pharmacist immediately;.
- An erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, seek medical help immediately. Priapism can permanently damage your penis.
- Sudden vision loss in one or both eyes. Sudden vision loss in one or both eyes can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy (NAION). Stop taking Sildenafil and call your healthcare provider right away if you have sudden vision loss in one or both eyes..
- Sudden hearing decrease or hearing loss. Some people may also have ringing in their ears (tinnitus) or dizziness. If you experience these symptoms, stop taking Sildenafil and contact a doctor right away.
For a full list of side effects, please read the patient information leaflet.
Alternatives
Although Sildenafil provides the most affordable treatment, it may not always be best suited to your needs. Levitra (or Vardenafil) is the most suitable treatment for people who suffer from diabetes, while Cialis (or Tadalafil), provides a longer-lasting effect. There is also now an over the counter option of Sildenafil in the form of Viagra Connect. This contains Sildenafil 50mg .
Vitaros cream is another alternative to oral medications in treating erectile dysfunction. If you have difficulty swallowing tablets, Nipatra (chewable sildenafil), is available.
Sildenafil Oral Jelly is another alternative, however this is an unlicensed treatment in the UK, and is not available to buy from a legal online pharmacy.
You can also look at counselling since some men suffer from erectile dysfunction as a result of nerves. If you think your ED is psychological, therapy may provide long term benefits if successful .
Comparisons of Sildenafil with other main ED medications are below.
Prices
Sildenafil 25mg Tablets (Viagra Generic)
| 2 tablets | £1.00 |
| 4 tablets | £5.89 |
| 8 tablets | £9.49 |
| 16 tablets | £17.19 |
| 32 tablets | £32.49 |
| 64 tablets | £45.50 |
Sildenafil 50mg Tablets (Viagra Generic)
| 2 tablets | £4.25 |
| 4 tablets | £7.49 |
| 8 tablets | £13.89 |
| 16 tablets | £23.00 |
| 32 tablets | £44.00 |
| 64 tablets | £63.95 |
Sildenafil 100mg Tablets (Viagra Generic)
| 2 tablets | £4.75 |
| 4 tablets | £8.19 |
| 8 tablets | £15.24 |
| 16 tablets | £25.99 |
| 32 tablets | £42.95 |
| 64 tablets | £71.95 |
Written by Qualified Experts
All of our medication and condition content is written by UK qualified pharmacists and doctors.
Reviewed: 20/03/2025
Further Reading
- Is There a Viagra for Women?
- How Long Does Viagra Take to Work?
- How Long Can the Average Man Stay Erect?
- What to Expect When First Taking Viagra?
- Is Bluechew Available In The UK?
- The Blue Pill - What Exactly Is It?
- Cialis vs Viagra
- Which Strength of Sildenafil is Best?
- Viagra vs Viagra Connect
- Can I Buy Viagra Without a Prescription
FAQ
General Information
What is Sildenafil?
Sildenafil is a PDE5 inhibitor used to treat erectile dysfunction (ED). It’s the generic version of Viagra and works by increasing blood flow to the penis during sexual stimulation.
Is Sildenafil the same as Viagra?
Yes. Sildenafil is the generic form of Viagra, containing the same active ingredient. The main difference is cost, as generics are typically cheaper.
Can Sildenafil treat other conditions?
Yes. Originally developed for pulmonary hypertension (under the name Revatio), it’s also prescribed off‑label for altitude sickness.
How does Sildenafil work?
It inhibits the PDE5 enzyme, relaxing blood vessels in the penis to improve blood flow, enabling an erection when sexually aroused.
Usage & Dosage
What is the standard dosage?
Typical doses are 25mg, 50mg, or 100mg. Most start with 50mg taken 30–60 minutes before sexual activity. The maximum dose is 100mg per 24 hours.
Can I adjust my dose?
Your doctor may adjust your dose based on effectiveness and side effects. Never exceed 100mg daily.
Should I take Sildenafil with food?
A light meal is acceptable, but avoid high‑fat meals as they can delay absorption by up to 1 hour.
What if I miss a dose?
Sildenafil is taken “as needed.” Simply skip the missed dose and take the next one when required.
Effectiveness & Results
How long does Sildenafil take to work?
Typically, it takes 30–60 minutes for Sildenafil to work, with effects lasting up to 4–5 hours.
What if Sildenafil doesn’t work?
Consult your doctor. Underlying health issues such as diabetes or vascular disease may require dose adjustments or alternative treatments.
Does Sildenafil cure ED?
No. It temporarily restores erectile function but does not address the underlying causes of ED.
Can I use Sildenafil for premature ejaculation?
It is not licensed for premature ejaculation, though some studies suggest it may help when used in combination with psychological therapy.
Side Effects & Safety
What are common side effects?
Common side effects include headaches, flushing, indigestion, nasal congestion, dizziness, and blurred vision.
Are there serious risks?
Rare but serious risks include priapism (a prolonged erection lasting more than 4 hours), sudden vision or hearing loss, and cardiovascular events. Seek immediate help if these occur.
Is Sildenafil safe for heart patients?
It is not recommended for patients taking nitrates (e.g., angina medication) or those with severe heart disease. A cardiac assessment may be necessary.
Can I use Sildenafil with alcohol?
Avoid excessive alcohol, as it can worsen side effects such as dizziness and may reduce the medication’s effectiveness.
Interactions
What drugs interact with Sildenafil?
Sildenafil interacts with nitrates (e.g., GTN spray) which can cause dangerous drops in blood pressure, alpha‑blockers (e.g., doxazosin), and other ED medications such as Tadalafil, increasing the risk of overdose.
Does Sildenafil affect blood pressure?
It may cause a temporary drop in blood pressure, especially if combined with alcohol or certain medications.
Storage
How should I store Sildenafil?
Store Sildenafil in a cool, dry place below 25°C. Protect from light and moisture, and keep it out of reach of children.
Does Sildenafil expire?
Yes. Discard expired tablets as they may lose potency or become unsafe.
Access & Cost
Is Sildenafil available on the NHS?
Yes, for erectile dysfunction if deemed clinically appropriate. Private prescriptions are also available.
Can I buy Sildenafil online?
Yes, from regulated UK online pharmacies (such as Simple Online Pharmacy) after a clinician approves your prescription.
How much does Sildenafil cost?
Prices range from approximately £0.71 per tablet (generic) to over £10 per tablet for branded Viagra, depending on strength and quantity.
Is a prescription required?
Yes. Sildenafil is a prescription‑only medication (POM) in the UK.
Are there cheaper alternatives?
Generic Sildenafil is the most cost‑effective option. Tadalafil (Cialis) is a longer‑acting alternative but is usually more expensive.
Compare
Treatment Comparison
| Sildenafil | Viagra | Tadalafil | Cialis | Vardenafil | Levitra | Spedra | |
| Active Ingredient | Sildenafil | Sildenafil | Tadalafil | Tadalafil | Vardenafil | Vardenafil | Avanafil |
| Time to Take Effect | 30-60 mins | 30-60 mins | 15-45 mins | 15-45 mins | 30-60 mins | 30-60 mins | 15-30 mins |
| Duration of Action | 4-6 hours | 4-6 hours | 24-36 hours | 24-36 hours | 4-6 hours | 4-6 hours | 4-6 hours |
| Unique Feature | Same active ingredient as Viagra | Most well known | Same active ingredient as Cialis | Longest Acting | Used for diabetics | Used for diabetics | Quickest Acting |
| Price Per Tablet | From 78p | From £4.84 | From 67p | From £2.26 | From £2.74 | From £2.97 | From £2.97 |
Reviews
Info Leaflet
Before taking Sildenafil or any medication, it is important to read the Patient Information Leaflet.
Warnings
Cautions
Alpha-blockers and Sildenafil
If you are taking alpha-blocking medicines for high blood pressure or pulmonary arterial hypertension, such as tamsulosin or trazodone, you are advised to leave at least six hours between taking your alpha-blocker and Sildenafil.
Nitrates and Sildenafil
Sildenafil cannot be prescribed by our doctor if you are taking nicorandil or nitrate-based medication, such as GTN spray or isosorbide mononitrate tablets for angina, chest pain or heart problems. It is not recommended to take SIldenafil if you are at risk of a heart attack.
