Viagra UK Guide 2025
Everything you need to know about Viagra (sildenafil) in the UK - how it works, correct dosage, side effects, and how to get it safely.
30-60 min
Time to work
4-6 hours
Duration
~80%
Success rate
How Viagra Works
Viagra contains sildenafil, a PDE5 inhibitor that was originally developed to treat heart conditions. It works by:
- Blocking PDE5 enzyme: This enzyme normally breaks down a chemical called cGMP, which relaxes blood vessel walls.
- Increasing blood flow: With PDE5 blocked, cGMP levels increase, causing blood vessels in the penis to relax and widen.
- Enabling erection: The increased blood flow makes it easier to achieve and maintain an erection when sexually aroused.
Important: Viagra does not cause automatic erections. Sexual stimulation is still required for the medication to work.
Viagra Dosage Guide
Who it's for: Men who experience side effects at higher doses, older men, or those with mild liver/kidney issues
May be sufficient for mild ED
Who it's for: Standard starting dose for most men
Effective for most men with ED
Who it's for: Men who don't respond adequately to 50mg
Maximum recommended dose
Dosage Safety
- • Never take more than one dose in 24 hours
- • Never exceed 100mg in a single dose
- • Take 30-60 minutes before planned sexual activity
- • Avoid heavy meals before taking - they can delay effects
Side Effects
Common Side Effects
| Side Effect | Frequency |
|---|---|
| Headache | Up to 16% |
| Facial flushing | Up to 10% |
| Indigestion | Up to 7% |
| Nasal congestion | Up to 4% |
| Dizziness | Up to 3% |
| Visual disturbances | Up to 3% |
Most side effects are mild and temporary, typically lasting a few hours. They often reduce with continued use as your body adjusts.
- Priapism: An erection lasting more than 4 hours (can cause permanent damage)
- Sudden vision loss: In one or both eyes
- Sudden hearing loss: Sometimes with ringing or dizziness
- Chest pain: Or irregular heartbeat during sex
Who Should Not Take Viagra
Viagra is not suitable for everyone. Do not take Viagra if you:
- Take nitrates: For chest pain or heart conditions (e.g., GTN spray, isosorbide). The combination can cause a dangerous drop in blood pressure.
- Take riociguat: For pulmonary hypertension
- Have had a recent stroke or heart attack: Within the last 6 months
- Have severe heart or liver problems: Including unstable angina or severe heart failure
- Have low blood pressure: Below 90/50 mmHg
- Have certain eye conditions: Including NAION (non-arteritic anterior ischemic optic neuropathy)
Always Disclose Your Medical History
When obtaining Viagra, always provide a complete medical history including all medications, supplements, and health conditions. This ensures the medication is safe for you.
How to Get Viagra Safely in the UK
Available from pharmacies after a consultation with the pharmacist.
- Available at high street pharmacies
- Online pharmacies with consultation
- Fixed 50mg dose only
Cost: £20-30 for 4 tablets (varies by pharmacy)
Available in all doses (25mg, 50mg, 100mg) with a prescription.
- NHS prescription (limited criteria)
- Private prescription from GP or online
- Generic sildenafil is much cheaper
Cost: From £1-2 per tablet (generic) to £20+ (branded)
Never buy Viagra from websites without proper pharmacy registration. Counterfeit ED medications are common and may contain:
- • No active ingredient at all
- • Wrong dosages (too much or too little)
- • Dangerous contaminants or other drugs
- • Ingredients not listed on packaging
Viagra vs Generic Sildenafil
Since Pfizer's patent expired in 2013, generic sildenafil has been available in the UK at much lower prices.
| Feature | Branded Viagra | Generic Sildenafil |
|---|---|---|
| Active ingredient | Sildenafil citrate | Sildenafil citrate |
| Effectiveness | Same | Same |
| Safety | Same | Same |
| Approximate cost | £15-25 per tablet | £1-5 per tablet |
Generic sildenafil is equally effective and safe. The only difference is the price and branding. Both are regulated by the MHRA.
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Frequently Asked Questions
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Medical Disclaimer
This information is for educational purposes only and does not constitute medical advice. Erectile dysfunction can be a sign of underlying health conditions including cardiovascular disease. Always consult a healthcare provider before taking ED medication to ensure it's safe for you. Never take ED medication with nitrates.
Last updated: December 2025