You took the tablet, waited, and nothing much happened. It is a common experience, and it does not mean nothing can help you. European urology guidelines say the most common reason erection tablets seem not to work is that they are not being taken in the right way, and that simple advice about dose, timing and sexual stimulation can turn many “non-responders” around1.
This guide covers the everyday reasons ED tablets fail, how to give them a fair trial, when switching or changing the dose makes sense, and what comes next if tablets are not enough.
First checks: the everyday reasons tablets fail
- No sexual stimulation. These medicines do not cause an erection on their own. They help your body respond when you are aroused4. Taking a tablet and waiting for something to happen usually ends in disappointment.
- Wrong timing. People often try too soon, or wait too long1. Each medicine has its own timing, shown in the table below.
- A heavy, fatty meal. A high-fat meal can slow down sildenafil, vardenafil and avanafil1. With sildenafil, it delayed the peak level by about an hour2. Tadalafil is not affected by food3.
- Too much alcohol. Drinking too much is a common cause of erection problems on its own6. Heavy drinking (5 units or more) with tadalafil can also cause dizziness and a drop in blood pressure when you stand up3.
- Nerves. Worry about whether the tablet will work can itself get in the way. More on this below.
| Medicine | When to take it | Food | Highest licensed dose |
|---|---|---|---|
| Sildenafil (Viagra) | About 1 hour before sex; it can be taken from 30 minutes to 4 hours before2 | A high-fat meal can delay it2 | 100 mg, once a day2 |
| Tadalafil (Cialis), as needed | Before sex; it can help for up to 36 hours3 | Not affected3 | 20 mg, once a day3 |
| Tadalafil, daily | Same time every day, whatever your plans3 | Not affected3 | 5 mg a day3 |
| Vardenafil (Levitra) | About 1 hour before sex4 | A high-fat meal can reduce the peak level4 | 20 mg, once a day4 |
| Avanafil (Stendra, Spedra) | About 15 minutes before (100 or 200 mg), or 30 minutes (50 mg)5 | A high-fat meal can slow it1 | 200 mg, once a day5 |
Our guide to how to take sildenafil goes into timing in more detail.
Have you given it a fair trial?
One failed attempt does not tell you much. The British Heart Foundation notes that you may need to take several doses over time before these medicines work properly, and that the dose may need adjusting7. A first attempt is often the most nervous one.
Before you decide a medicine does not work for you, try it on several separate occasions, taken the right way, at a relaxed time, with enough arousal. Then talk to your prescriber about what happened.
Dose: what can and cannot change
The labels allow the dose to go up or down depending on how well it works and how well you tolerate it23. So if a lower dose has not worked, your prescriber may suggest a higher one, up to the licensed maximum in the table above.
- Do not go above the licensed maximum, and do not take more than one dose a day23. Higher doses mainly bring more side effects2.
- Some medicines need a lower dose, not a higher one. Some HIV medicines, some antibiotics and antifungals, and alpha-blockers for blood pressure or the prostate all change how much ED medicine is safe23.
- Do not mix two ED medicines on your own. The safety of combining them has not been studied, they may lower blood pressure further, and the label advises against it2.
Is it genuine medicine?
The European guidelines ask doctors to check that a patient who is not responding is actually using a licensed medicine1. The US Food and Drug Administration warns that many “natural” or “herbal” sexual enhancement products sold online and in shops contain dangerous hidden ingredients9. Use a regulated pharmacy that asks for a prescription, and check that the pack names the active ingredient and strength.
Switching to a different medicine
Studies have not shown that any one of these medicines works better than the others overall1. But they differ in practical ways that can matter to you:
- Tadalafil lasts longest, which takes the pressure off timing3. See sildenafil vs tadalafil.
- Daily low-dose tadalafil means you do not have to plan around a tablet at all3. See daily vs on-demand tadalafil.
- Avanafil can be taken closer to sex5. See avanafil vs sildenafil.
- Vardenafil is another option with similar timing to sildenafil4. See our vardenafil comparison.
For harder cases, specialists sometimes combine daily tadalafil with a short-acting tablet, or a tablet with another treatment1. That is a decision for a specialist, not something to try yourself.
Hidden causes worth checking
If tablets still do not work when taken correctly, something else may be getting in the way. Common culprits include6:
- Diabetes, high blood pressure or high cholesterol, which damage the blood vessels and nerves erections depend on.
- Low testosterone. In men with low testosterone who do not respond to tablets, testosterone treatment may improve the response1. A blood test can check this.
- Other medicines, which can cause erection problems as a side effect. Your doctor may be able to switch you6.
- Depression, anxiety or relationship stress. Guidelines recommend talking therapy, including your partner where it helps, alongside medicine1.
When tablets are not enough
Tablets are only the first step. The European guidelines list several other treatments1:
- Injections into the penis with a medicine called alprostadil.
- Alprostadil cream or a small pellet placed in the urethra, for men who do not want injections.
- A vacuum pump, a drug-free device that draws blood into the penis6.
- Low-intensity shockwave treatment, for some men with mild ED caused by poor blood flow.
- A penile implant, if other treatments fail or by choice.
A urologist or men’s health clinic can talk you through these.
When to see a doctor
- If you have not had a check-up for your ED. Erection problems can be an early warning sign of narrowed arteries and heart disease7. Heart experts now advise treating men with ED as at risk of heart problems until shown otherwise8.
- If a tablet that used to work has stopped working. Something may have changed, such as a new medicine or a new health problem.
- Straight away if an erection lasts more than 4 hours, or if you get sudden loss of vision or hearing after taking an ED tablet2.
Our ED medicines page lists the treatments we supply, including Viagra 50 mg and Cialis 5 mg, and our guide to ED medication side effects covers what to expect.
Frequently asked questions
Why is Viagra not working for me?
The most common reasons are taking it without sexual stimulation, taking it too soon or after a heavy meal, drinking too much, or nerves. If you have tried it properly several times, ask your prescriber about the dose, a different medicine, or a check for other causes such as diabetes or low testosterone.
What should I do if Cialis does not work?
Check that you are allowing enough time and enough arousal, and that you have tried it on several occasions. Your prescriber may adjust the dose, try daily tadalafil, or switch you to another medicine. If tablets still do not help, other treatments are available.
Does Viagra stop working over time?
If a tablet that used to work no longer does, the cause is usually a change in you rather than the medicine, such as a new health problem, a new medicine or more stress. See a doctor, because new or worse erection problems can be a sign of heart or blood vessel disease.
Can I take a higher dose?
Only up to the licensed maximum and only if your prescriber agrees: 100 mg for sildenafil, 20 mg for tadalafil or vardenafil, and 200 mg for avanafil, no more than once a day. Some people need a lower dose because of other medicines they take.
How many times should I try before giving up?
Do not judge a medicine on one attempt. Try it on several separate occasions, taken the right way, and then discuss the results with your prescriber.
Can I take Viagra and Cialis together?
No, not on your own. Combining ED medicines has not been properly studied and the labels advise against it. Specialists occasionally combine treatments for difficult cases under close supervision.
Sources & references
- European Association of Urology. EAU Guidelines on Sexual and Reproductive Health: Management of erectile dysfunction.
- US National Library of Medicine, DailyMed. Viagra (sildenafil) prescribing information.
- US National Library of Medicine, DailyMed. Cialis (tadalafil) prescribing information.
- US National Library of Medicine, DailyMed. Vardenafil tablets prescribing information.
- US National Library of Medicine, DailyMed. Stendra (avanafil) prescribing information.
- NHS. Erectile dysfunction (impotence). Page last reviewed 28 July 2023.
- British Heart Foundation. Erectile dysfunction, Viagra and your heart. Updated 29 May 2026.
- Kohler TS, Kloner RA, et al. The Princeton IV Consensus Recommendations for the Management of Erectile Dysfunction and Cardiovascular Disease. Mayo Clin Proc. 2024;99(9):1500-1517.
- US Food and Drug Administration. Sexual Enhancement and Energy Product Notifications. Content current as of 25 September 2026.
Related reading
- Can you take Viagra every day?
- ED or low testosterone?
- Kamagra vs Viagra
- What is erectile dysfunction?
- ED medicines overview
- Sildenafil medicines
- Tadalafil medicines
This content is for informational purposes only and is not medical advice. Never take more than the licensed dose, and never take ED medicines with nitrates. Used as prescribed by a licensed medical professional.
Sitharam Reddy is a licensed clinical pharmacist with 19 years of experience. He holds a B.Pharm and M.Pharm from Rajiv Gandhi University of Health Sciences. At OnlineMeds, he reviews medicine and health content to help ensure it is accurate, evidence-based, and easy to understand.