Short answer: Sildenafil, the medicine in Viagra, may seem not to work because of how it was taken: its UK leaflet says to take it about an hour before sex, that it can take longer to work after a heavy meal, and that alcohol can make an erection harder to get (Viagra patient leaflet, sections 2 and 3). These tablets only work with sexual stimulation. Try a tablet 4 to 8 times before deciding it does not work, then tell us. Never take more than one tablet in 24 hours. Do not take more than the dose you were supplied: 100mg is the highest dose in the UK product information (Viagra SmPC, section 4.2), and the leaflet says doses above 100mg do not work better. If it still does not work, the cause may be a dose that is too low for you, a health problem, another medicine, anxiety or fake tablets, so tell us: at your next order the pharmacist can review your dose or consider a different medicine, and a GP can look for the cause.
This guide sets out what the UK product information for Viagra and Cialis, the NHS, the British Association of Urological Surgeons (BAUS) and the MHRA say, as of October 2026: each reason and what to try, what happens if 100mg does not work, tadalafil (Cialis), fake tablets, and when to see a GP. We supply sildenafil tablets in 25mg, 50mg and 100mg after a consultation reviewed by a GPhC-registered pharmacist.
Why is Viagra not working for me?
Viagra (sildenafil) may not be working because of how or when it was taken, because it has not had enough tries, or because of a dose that is too low for you, a health problem, another medicine, stress or anxiety, or fake tablets. The table sets out each reason and what to try, and the sections below explain them.
| Reason | What to try |
|---|---|
| No sexual arousal | These tablets only work with sexual stimulation. They do not raise your sex drive, so allow time for arousal and foreplay, as you would without a tablet. |
| The wrong timing | Sildenafil: take it about 1 hour before sex (anywhere from 30 minutes to 2 hours before). It takes about an hour to work. |
| A heavy or high-fat meal | A heavy or high-fat meal can delay how quickly it works. If you plan to eat a big meal, allow more time. |
| Too much alcohol | Drinking less alcohol can help your erections. The Viagra leaflet advises against drinking excessive amounts before you take it. |
| Too few tries | Try a tablet 4 to 8 times before deciding it does not work, then tell us. |
| A dose too low for you | Tell us when you reorder, and the pharmacist can review your dose (see below). |
| A health problem | See your GP if erection problems keep happening: the NHS says they might be a sign of a health condition that can be treated. |
| Another medicine | Tell us every medicine you take, including herbal remedies and supplements: the NHS says some do not mix well with sildenafil. Do not use unlicensed herbal remedies for erections, and do not stop any prescribed medicine unless your doctor tells you to. |
| Stress or anxiety | Talk to your GP: the NHS says counselling and therapy can help when erection problems are linked to emotional or mental health problems. |
| Fake tablets | Use only a registered UK pharmacy (in Great Britain, one on the General Pharmaceutical Council's register): the MHRA warns that unlicensed tablets may contain no active ingredient or the wrong dose. |
Does Viagra work the first time?
Not always, so do not judge it on one try. Try a tablet 4 to 8 times before deciding it does not work, then tell us.
The leaflet for Viagra Connect, which is sildenafil 50mg supplied after a pharmacist consultation with no prescription needed, says to relax and be patient if it does not help the first time, and that if it has been some time since you were able to get or keep an erection, it may take a couple of attempts (section 3). If a tablet has not helped, wait at least 24 hours before you take another. Less common side effects are listed in the leaflet in your pack. Please read it before your first dose.
Are you taking Viagra the right way?
The right way is one tablet, swallowed whole with water, about an hour before you plan to have sex, with time to become sexually aroused (Viagra patient leaflet, sections 1 and 3). Two parts of that need more explanation: food and arousal.
Food. A meal slows how quickly sildenafil gets into your blood: the UK product information says that, taken with food, it reaches its highest level about an hour later on average than on an empty stomach (Viagra SmPC, section 5.2). The leaflet says it may take longer to start working if you take it with a heavy meal (sections 2 and 3).
Arousal. When you are sexually aroused, your body releases nitric oxide in the penis. This sets off a chemical signal that relaxes the blood vessels there, so blood can flow in. Sildenafil works by slowing the breakdown of that signal, so without arousal there is no signal for it to act on (Viagra SmPC, section 5.1). More in how does Viagra work.
If you feel the effect is too weak, or too strong, the Viagra leaflet says to talk to your doctor or pharmacist (section 3). For timing in more detail, see how long sildenafil lasts.
The other tablets of this kind that we supply are tadalafil, vardenafil and avanafil, each with its own timing. A heavy or high-fat meal can delay how quickly sildenafil, vardenafil and avanafil work. Tadalafil is not affected by food.
Could alcohol, a medicine or a health problem be the cause?
Yes: too much alcohol, some medicines and some health conditions can each stop sildenafil working as well as it should, so tell us about all three.
Alcohol
The Viagra leaflet says drinking alcohol can temporarily make it harder to get an erection, and advises not drinking excessive amounts before you take it (section 2). The NHS says the same of sildenafil and of tadalafil. See Viagra and alcohol.
Other medicines
Erection problems can be a side effect of some medicines (nhs.uk), and BAUS names some blood pressure medicines, antidepressants, antipsychotics and antihistamines among them.
A few medicines can also lower the amount of the tablet in your blood. The UK product information says strong enzyme inducers such as rifampicin are expected to lower the level of sildenafil (Viagra SmPC, section 4.5), and that rifampicin lowers the level of tadalafil, which can be expected to make it work less well (Cialis SmPC, section 4.5). Our consultation does not supply these tablets to men taking rifampicin, phenobarbital, phenytoin, carbamazepine or St John's Wort.
If you think a medicine is the cause, speak to your GP or pharmacist before changing anything: your doctor may be able to switch you to a different one (nhs.uk). Do not use unlicensed herbal remedies for erections, and do not stop any prescribed medicine unless your doctor tells you to. See medicines that can cause erectile dysfunction.
Health problems
If erection problems happen often, the NHS says the cause may be a condition such as high blood pressure or high cholesterol, diabetes, depression or anxiety, or a hormone problem. In the trials described in the Viagra product information, men with diabetes, and men who had had surgery to remove the prostate, reported better erections less often than the other groups listed (SmPC, section 5.1). Your GP can check for these (see below), and the causes are explained in what is erectile dysfunction.
What if 100mg Viagra does not work?
Do not take more: 100mg is the highest dose in the UK product information (Viagra SmPC, section 4.2), and the Viagra leaflet says doses above 100mg do not work better and can bring more side effects, and more severe ones (section 3). Never take more than one tablet in 24 hours. See Viagra side effects.
Do not take a different erectile dysfunction tablet as well: the Viagra leaflet says not to use it with any other treatment for erectile dysfunction (section 2), and its product information says such combinations have not been studied and are not recommended (SmPC, section 4.4). We do not supply one to anyone already taking another.
If the reasons in the table above do not explain it, tell us. What the pharmacist can consider next depends on how it went:
When you reorder, we ask how your last tablets worked and whether you had any side effects.
- Your dose did not work well enough and caused no side effectsThe pharmacist can consider the next strength up. Sildenafil comes in 25mg, 50mg and 100mg, so there is no strength above 100mg.
- It caused side effectsYou can choose the same dose or, where there is one, a lower strength, and the pharmacist checks your answers before anything is sent.
- A medicine has not worked after 4 to 8 tries at the highest dose that suits youYour pharmacist may suggest trying a different one. If you switch to a different medicine, you start it at its starting dose, even if you took a higher dose of the one before.
- Already tried the maximum dose of two different erectile dysfunction medicines without successPlease see your GP, who can look for a cause such as low testosterone and may refer you to a specialist.
The pharmacist decides whether a medicine and a dose are right for you.
If the pharmacist cannot approve your order, we refund you in full. How the tablets differ is in sildenafil vs tadalafil, and the dose steps in sildenafil dosage.
Answer a few questions about your health and the medicines you take. A GPhC-registered pharmacist reviews every consultation, and if they cannot approve your order, we refund you in full.
Start your consultationWhat if tadalafil (Cialis) does not work?
If tadalafil is not working, check the same things, allowing for its own timing and limits: like sildenafil, it only works with sexual stimulation (Cialis SmPC, section 4.1), but food does not affect it.
- Timing: Take it at least 30 minutes before sex. It takes about 30 to 45 minutes to work, and its effect can last more than 24 hours.
- Food: Tadalafil is not affected by food.
- Alcohol: the NHS says drinking alcohol with tadalafil can make low blood pressure more likely, which can make you feel dizzy or light-headed, and that too much alcohol can make an erection more difficult.
- How often: Take one tablet no more than twice a week, and never more than once in 24 hours.
- The dose: tadalafil taken when needed comes in 10mg and 20mg, and its UK product information says that if 10mg does not work well enough, 20mg might be tried (Cialis SmPC, section 4.2). At a repeat order the pharmacist can consider 20mg when 10mg did not work well enough and caused no side effects, unless a liver problem, or a medicine such as erythromycin, diltiazem or verapamil, keeps you to 10mg.
Daily tadalafil is one option the pharmacist may consider. It is for men who expect to have sex at least twice a week. The available data does not suggest that taking it every day works better than taking tadalafil when needed. More on the daily tadalafil page, and on timing in how long tadalafil lasts.
Could your Viagra be fake?
It could be, if it did not come from a registered pharmacy, and a fake tablet may not work at all: the MHRA warns that unlicensed erectile dysfunction tablets may contain no active ingredient, the wrong dose, hidden drugs or toxic ingredients. It seized about 19.5 million doses of them from 2021 to 2025, many sold online (MHRA, 13 February 2026). The NHS warns that many websites sell fake medicines, and that the ingredients of medicines bought online can vary from one pack to another.
What the MHRA advises
- Avoid buying medicines from social media, messaging apps or unknown websites.
- Only use UK-registered pharmacies. For an online pharmacy based in Great Britain, check that it is on the General Pharmaceutical Council's register.
- Report suspicious medicines or websites through the MHRA's Yellow Card scheme.
QuickCare Pharmacy, the registered pharmacy that dispenses Solira orders, is on that register: GPhC 9013213.
How to check a medicine is genuine, and what to do if you think yours is not, is on our safety page.
When should you see your GP?
See your GP, or a sexual health clinic, if erection problems keep happening or tablets have not helped: the NHS says erection problems that keep happening might be a sign of a health condition that can be treated. If this is your first time with erection problems, see your GP to check your blood sugar, cholesterol and testosterone, and have a heart health check at least every 5 years.
The Viagra leaflet also says to tell your doctor if it does not help you get an erection, or if the erection does not last long enough to finish sex (section 3). Your GP can look for a cause, and BAUS says that if tablets do not work, cause significant side effects or cannot be used, the GP can refer you to a local erectile dysfunction clinic, which has other treatments.
Severe erection problems need a face to face review, so we do not treat them online. If the five questions in our consultation point to severe erectile dysfunction, the consultation stops, and its advice is: please book a GP appointment to have this assessed. Your GP may refer you onward to cardiology, urology or endocrinology, as severe symptoms can be an early sign of another condition.
How can you make erectile dysfunction tablets work better?
Take each tablet as its leaflet says, give it enough tries, never take more than the dose you were supplied, and look after the rest of your health. Losing weight, stopping smoking, drinking less alcohol and exercising can all help. If you cycle more than 3 hours a week, try a break from cycling. The NHS also advises a healthy diet, daily exercise, trying to reduce stress and anxiety, and no more than 14 units of alcohol a week.
If stress, anxiety or another emotional or mental health problem plays a part, the NHS says counselling and therapy can help, although there can be a long wait on the NHS. Privately, it says sex therapists should be members of the College of Sexual and Relationship Therapists (COSRT) or the Institute of Psychosexual Medicine.
If tablets do not help or do not suit you, there are other treatments, from vacuum pumps to injections from a specialist clinic: see alternatives to Viagra, or all our erectile dysfunction treatments.