Viagra (Sildenafil) has helped millions of men worldwide manage erectile dysfunction (ED). 

When taken correctly, it can restore confidence, improve sexual performance, and make your sexual experience positive.  

However, getting the best results depends on knowing how Viagra works and how to use it properly. 

What men should know before taking Viagra

1. Make sure Viagra is safe for you to take

Viagra is safe and effective for most men, with minimal side effects when used correctly. Since becoming available over the counter in 2019, it has been widely used across the UK.

However, Viagra is not suitable for everyone. You should avoid it if you take nitrate-based medicines (often prescribed for chest pain or heart problems), or if you have certain medical conditions such as severe heart or liver disease.

If you’re unsure whether Viagra is suitable for you, consult a doctor or pharmacist before taking it.

2. It may not work the first time

Viagra may not work the first time you take it.

Factors such as stress, anxiety, alcohol, or heavy meals can all affect its absorption and effectiveness.

Most men find that Viagra works best after trying it a few times, with consistent timing and correct use.

3. You need to be sexually aroused

Viagra doesn’t automatically cause an erection. It only helps when you’re sexually stimulated.

When you’re aroused, your body releases a chemical called cGMP, which relaxes blood vessels in the penis and increases blood flow, allowing you to get and maintain an erection.

4. Viagra will not change the size of your penis

There are common myths about Viagra increasing penis size. However, this is not true.

Viagra will:

  • Help men with ED achieve and maintain an erection during sex

Viagra will not:

  • Permanently increase penis size
  • Delay ejaculation if you have premature ejaculation

The effects of Viagra usually last for up to 4 hours. Take it 30-60 minutes before sexual activity.

5. Take Viagra on an empty stomach

A heavy or fatty meal can delay Viagra absorption and reduce its effectiveness.

For best results, take Viagra on an empty stomach or after a light meal, and avoid taking it right after eating.

6. Avoid excess alcohol

Alcohol can reduce blood flow to the penis, working against Viagra. It can also worsen side effects such as dizziness and flushing.

If alcohol helps you relax, limit yourself to one or two units for the best results.

Further reading: Viagra and Alcohol

7. Use the correct dose

The usual starting dose is 50mg, taken about an hour before sex.

If you experience side effects, try lowering it to 25mg.

If 50mg isn’t effective and you have no side effects, your doctor may increase your dose to 100mg.

Always speak to a healthcare professional before changing your dose.

8. Time your dose correctly

Take Viagra around one hour before sex.

If taken too early, its peak effects may fade; if taken too late, there may not be enough time for it to reach effective levels in your bloodstream.

9. Check for underlying health conditions

Conditions such as diabetes, heart disease, or high blood pressure can impact your ability to get an erection.

Hormonal issues like low testosterone or thyroid imbalances may also play a role.

Addressing these with your doctor can improve your response to Viagra and your overall health.

10. Manage stress and performance anxiety

Anxiety can block sexual arousal and reduce the effectiveness of Viagra.

For men with performance anxiety, Viagra can help by building confidence and easing worry.

Practising relaxation and focusing on enjoyment can further enhance results.

11. Purchase Viagra from reputable sources

Only purchase Viagra from registered UK pharmacies.

You can check a website’s registration on the General Pharmaceutical Council (GPhC) register.

Avoid unverified online sellers offering cheap or “alternative” Viagra (such as Kamagra). These may be counterfeit or unsafe.

What happens after taking Viagra?

Viagra doesn’t work instantly. Here’s a typical timeline of what to expect after taking a dose: 

Time What Happens
15 minutes Some men experience results as early as 12-15 minutes (especially on an empty stomach).
30-60 minutes Most men notice Viagra working. This is when it reaches peak effectiveness.
4 hours Viagra remains active, but its effect gradually reduces as the drug begins to wear off.
10-12 hours Some men may still notice mild effects, but erections are less likely to occur.
24 hours Viagra is fully cleared from your system. You can take another dose the next day if needed.

If Viagra doesn’t seem to work the first time, try again on another occasion, following all the guidance above. 

What to do if you are not getting the desired results with Viagra

If  Viagra doesn’t work the first time you take it, don’t give up. The UK national guidelines recommend that you take Viagra on eight separate occasions before deciding if it is working or not. This gives your body time to adjust.

If you are still not getting results after using Viagra correctly, speak to you prescriber.

They may:

  • Adjust your dose
  • Check for underlying conditions
  • Suggest alternatives such as tadalafil (Cialis), which lasts up to 36 hours

Key Takeaways

  • Viagra works best when taken correctly, about 30-60 minutes before sex.
  • You need to be sexually aroused for it to work.
  • Avoid heavy meals and excess alcohol.
  • Consult your doctor if it doesn’t work or causes side effects.

  1. McMurray JG, Feldman RA, Auerbach SM, DeRiesthal H & Wilson N, ‘Long-term safety and effectiveness of sildenafil citrate in men with erectile dysfunction’, Therapeutics and Clinical Risk Management, Dec 2007; 3(6): 975-981. (Accessed: 5 November 2025). From: https://pmc.ncbi.nlm.nih.gov/articles/PMC2387281/

Whilst all of our content is written and reviewed by healthcare professionals, it is not intended to be substituted for or used as medical advice. If you have any questions or concerns about your health, please speak to your doctor.

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