Sildenafil
• The same active ingredient as Viagra, as a lower-cost generic
• 25mg, 50mg and 100mg tablets (manufacturer may vary)
• Take about 1 hour before sex; works for around 4 to 5 hours
• Maximum one tablet in 24 hours
• Prescription medicine: a UK prescriber reviews your consultation before dispatch
£4.99 – £17.99
Sildenafil tablets are a prescription treatment for erectile dysfunction (ED) in adult men. Sildenafil is the same active ingredient as Viagra, supplied here as a generic medicine in 25mg, 50mg and 100mg tablets. To get sildenafil from Bury Healthcare Online you complete a short online consultation, and a UK prescriber reviews your answers before anything is dispatched.
How to get sildenafil tablets online
- Choose your strength and pack size, then select Start Consultation. Your choice is a preference: the final decision is made with your prescriber.
- Complete a short online consultation about your health, blood pressure and any medicines you take. It takes about 5 to 10 minutes.
- A UK prescriber reviews your answers before anything is dispatched. They may ask you questions, suggest a different medicine or strength, or decide treatment is not suitable. If it is not suitable, you get a full refund.
- Approved orders are dispatched from our GPhC-registered pharmacy in Bury (GPhC 1126145).
We supply up to 16 tablets per order. Every order is reviewed by a prescriber.
What is sildenafil?
Sildenafil is the active ingredient in Viagra. Generic sildenafil tablets contain the same medicine at the same strengths and are made to the same UK standards, but cost less because they do not carry the brand name. The manufacturer of the generic tablets we supply may vary. If you would prefer the branded version, see Viagra.
How sildenafil works
Sildenafil is a PDE5 inhibitor. During sexual arousal it helps the blood vessels in the penis relax, so more blood can flow in and an erection is easier to get and keep. It does not cause an erection on its own: you still need to be sexually stimulated. It does not increase sex drive and is not a cure for erectile dysfunction.
Who should not take sildenafil
Sildenafil is for adult men aged 18 or over with erectile dysfunction. Do not take it if:
- You are allergic to sildenafil or any of the other ingredients.
- You take any nitrate medicine for chest pain (for example glyceryl trinitrate (GTN) spray or tablets, isosorbide mononitrate or isosorbide dinitrate), or use “poppers” (amyl nitrite or other nitrites). The combination can cause a dangerous drop in blood pressure.
- You take riociguat for pulmonary hypertension.
- Your doctor has advised you not to have sex because of a heart problem, or you have unstable angina or severe heart failure.
- You have had a heart attack or stroke recently, or you have low blood pressure (below 90/50).
- You have ever lost sight in an eye because of reduced blood flow to the optic nerve (NAION), or you have an inherited eye condition such as retinitis pigmentosa.
- You have severe liver problems.
Tell your prescriber about:
- Heart problems, high or low blood pressure, or an irregular heartbeat
- Liver or kidney problems
- A bleeding disorder or an active stomach ulcer
- A condition that affects the shape of the penis (such as Peyronie’s disease), or a condition that makes a long-lasting erection more likely (such as sickle cell anaemia, multiple myeloma or leukaemia)
- Other medicines, especially alpha-blockers (for example doxazosin or tamsulosin), other blood pressure medicines, HIV medicines (such as ritonavir), certain antifungals (ketoconazole, itraconazole) and certain antibiotics (clarithromycin, erythromycin)
- Any other treatment for erectile dysfunction
The consultation asks about all of these. Some answers mean we cannot supply online and will direct you to your GP.
How to take sildenafil
- Take one tablet with water about 1 hour before sex. It can work from around 30 minutes, but this varies.
- It works for around 4 to 5 hours, and you can have an erection during this time if you are aroused.
- Taking it after a heavy or fatty meal can delay how quickly it works.
- Do not take more than one tablet in 24 hours, and do not take it with other erectile dysfunction treatments.
- Avoid drinking a lot of alcohol, which makes erections harder and can increase side effects. Grapefruit juice can raise the amount of sildenafil in your blood.
| Strength | Usually used for |
|---|---|
| 25mg | A lower starting dose, for example if you take an alpha-blocker, certain other medicines, or have liver or severe kidney problems, or if 50mg caused side effects |
| 50mg | The usual starting dose for most men |
| 100mg | The maximum dose, if 50mg worked well but was not strong enough |
Your prescriber decides the right strength from your consultation answers.
Side effects
Like all medicines, sildenafil can cause side effects, although not everybody gets them. They are usually mild and short-lived.
- Very common (more than 1 in 10 men): headache
- Common (up to 1 in 10 men): flushing or feeling hot, indigestion, blocked nose, dizziness, feeling sick, a coloured tinge or blurring to your vision
See the safety section below for the rare but serious effects that need urgent help.
Sildenafil, tadalafil and vardenafil compared
All three are PDE5 inhibitors and work in the same way. The main differences are how soon they start working, how long the window lasts and whether food makes a difference. Your prescriber can help you choose.
| Medicine | When to take it | Works for up to | Food |
|---|---|---|---|
| sildenafil / Viagra | About 1 hour before sex | About 4 to 5 hours | A heavy meal can delay it |
| tadalafil / Cialis (on demand) | At least 30 minutes before sex | Up to 36 hours | Not affected |
| tadalafil once a day / Cialis Once a Day | One tablet every day, same time | Continuous while taken daily | Not affected |
| vardenafil | 25 to 60 minutes before sex | About 4 to 5 hours | A high-fat meal can delay it |
Important safety information
Get medical help straight away (call 999 or go to A&E) if you have:
- An erection that lasts more than 4 hours
- Chest pain during or after sex. Tell the medical team you have taken an erectile dysfunction medicine, because nitrates must not be given to you.
- Sudden loss of vision or sudden loss or decrease in hearing. Stop taking the medicine.
- A severe allergic reaction, such as swelling of the face, lips or throat, or a severe skin reaction
This page is a summary. Always read the patient information leaflet supplied with your medicine. Erectile dysfunction can be an early sign of heart disease, diabetes or high blood pressure, so it is worth seeing your GP for a health check as well. You can report side effects through the MHRA Yellow Card scheme.
Medically reviewed by Hassan Khan, MPharm, Independent Prescriber — Superintendent Pharmacist, Bury Healthcare Online (GPhC-registered pharmacy 1126145). Last reviewed: October 2026. Information checked against the UK Summary of Product Characteristics.
