Taking Viagra for the First Time: What to Expect
Dosage, timing, common side effects, what to do if it doesn’t work, and safety essentials.
When to get urgent help: Call 999 if you get chest pain during or after sex (tell the paramedics you have taken sildenafil, as nitrates such as GTN must not be given), or signs of a serious allergic reaction. Go to A&E or call 999 if an erection is painful or lasts more than 4 hours (do not drive yourself). Stop sildenafil and get medical help immediately (contact your GP or NHS 111) if you have a sudden decrease or loss of vision or hearing. See your GP about new erection problems, as they can be an early sign of heart disease or diabetes.
Part of the Access Doctor Erectile Dysfunction guide.
Key fact: Viagra (sildenafil) doesn't cause an erection on its own. Sexual stimulation is always required. Understanding that — and getting the timing and dose right — is the most important preparation for your first time.
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Start Consultation →Choosing Your Starting Dose
| Dose | Who it suits | Notes |
|---|---|---|
| 25mg | Men with liver or severe kidney problems, those taking certain other medicines, or those who get side effects on 50mg | Lower side effect risk; may be less effective for some |
| 50mg (standard start) | Most men taking Viagra for the first time | Recommended starting dose; adjust up or down based on response |
| 100mg | Men in whom 50mg is insufficient, under prescriber guidance | Maximum dose; never exceed without prescriber approval |
Sildenafil is available as branded Viagra tablets or as generic sildenafil, which contains the same active ingredient. Your prescriber will confirm which strength is right for you.
Timing and How to Take Viagra
- Take it about 1 hour before sexual activity — it can start working from about 30 minutes
- Take on an empty stomach or after a light meal — a large, high-fat meal delays and reduces absorption
- Never take more than one tablet in any 24-hour period
- Avoid grapefruit juice — it blocks the enzyme that breaks down sildenafil, pushing drug levels (and side effect risk) up
- Avoid large amounts of alcohol — it impairs sexual function and worsens dizziness and flushing
- Sexual stimulation is required — Viagra enhances your natural response to arousal; it won't produce an erection without it
What Happens After You Take Viagra
Sildenafil is absorbed through the gut into the bloodstream. On an empty stomach it usually reaches its highest level in the blood about 1 hour after you take it (anywhere from 30 minutes to 2 hours), and a heavy meal can delay this. When you are sexually stimulated, PDE5 inhibition lets the smooth muscle in the penile blood vessels relax, increasing blood flow and making an erection easier. The effect usually lasts about 4 hours, though this varies from man to man.
Common First-Time Side Effects
| Side effect | How common | What to do |
|---|---|---|
| Headache | Very common (more than 1 in 10) | Usually mild; paracetamol if needed; resolves as the medication wears off |
| Facial flushing | Common | Temporary vasodilation effect; passes within an hour or two |
| Nasal congestion | Common | Temporary; saline nasal spray can help |
| Indigestion | Common | Try taking it with a light meal next time |
| Visual changes (such as a blue tinge or blurred vision) | Common | Usually brief; do not drive if your vision is affected |
| Dizziness | Common | Sit or lie down; worsened by alcohol and standing up quickly |
| Priapism (erection >4 hours) | Rare — medical emergency | Go to A&E or call 999 if an erection lasts more than 4 hours — don’t delay |
What to Do If Viagra Doesn’t Work the First Time
It's not uncommon for the first attempt to be suboptimal. Before you conclude Viagra isn't working for you, work through each of these:
- Timing — did you allow at least 30 minutes, preferably an hour?
- Food — did you take it after a large or fatty meal? Try on an empty stomach next time
- Anxiety — performance anxiety can stop Viagra from working properly; relax and let arousal build without pressure
- Alcohol — even moderate drinking can blunt the response
- Try again — some men need several attempts at the right dose before it works well
If 50mg is consistently insufficient after correct use, speak to your prescriber. They may recommend 100mg or a switch to tadalafil. See our tadalafil vs sildenafil comparison.
Get urgent help if an erection lasts more than 4 hours (go to A&E or call 999), or if you get chest pain during or after sex (call 999). If you have a sudden decrease or loss of vision or hearing, stop taking Viagra and get medical help straight away.
UK safety and prescribing information
- Legal status: Viagra Connect 50mg is a pharmacy (P) medicine that men aged 18 and over can buy after a consultation with a pharmacist. Viagra 25mg, 50mg and 100mg tablets and all generic sildenafil are prescription-only medicines (POM). Access Doctor supplies MHRA-licensed UK medicines, dispensed by our GPhC-registered pharmacy (#9011198) only after a prescriber has assessed your consultation. It is illegal to sell or supply prescription-only medicines without a prescription in the UK.
- Maximum dose: no more than one tablet in 24 hours. The highest strength is 100mg.
- Interactions: never take sildenafil with nitrates (including GTN spray), nicorandil, “poppers” or riociguat. Tell your prescriber about alpha-blockers, other blood pressure medicines, HIV medicines such as ritonavir, and antifungals or antibiotics such as ketoconazole or clarithromycin.
- Driving: sildenafil can cause dizziness and changes in vision. Check how it affects you before driving or using machinery.
- NHS: in England and Scotland, your GP can prescribe generic sildenafil on the NHS for erectile dysfunction if it is suitable for you. Branded Viagra is only prescribed on the NHS in limited circumstances. In Wales, NHS prescribing of ED medicines, including generic sildenafil, is currently limited to men who meet certain criteria, and the rules may differ in Northern Ireland, so ask your GP. NHS prescription charges apply in England unless you are exempt; prescriptions are free in Scotland, Wales and Northern Ireland.
Frequently Asked Questions
What dosage of Viagra should I take the first time?
50mg is the recommended starting dose for most men. Your prescriber may reduce it to 25mg if needed, or increase it to 100mg if 50mg does not work well enough. Never take more than one tablet in 24 hours.
How long does Viagra take to work the first time?
It can start working from about 30 minutes. Take it about 1 hour before sex, on an empty stomach or after a light meal, as a heavy meal can delay it.
What if Viagra doesn’t work the first time?
Check the timing, avoid large fatty meals, and try to reduce anxiety. Some men need several attempts at the right dose. Speak to your prescriber if it keeps failing — a dose change or a switch to tadalafil may help.
Can I drink alcohol before taking Viagra?
A small amount of alcohol is unlikely to cause problems. Drinking a lot can make it harder to get an erection and can make side effects such as dizziness and flushing worse.
What side effects should I expect the first time?
Headache is the most common. Flushing, a blocked nose, indigestion, dizziness and mild vision changes (such as a blue tinge) are also common. These are usually mild and wear off as the medicine does.
Will Viagra work every time?
Not always. Most men find it improves their erections, but stress, tiredness, alcohol and relationship factors can all affect how well it works. If it keeps failing, speak to your prescriber about changing the dose or trying a different medicine.
References
- National Institute for Health and Care Excellence (NICE). Clinical Knowledge Summaries: Erectile dysfunction. cks.nice.org.uk
- NHS. Erectile dysfunction (impotence). nhs.uk
- NHS. Sildenafil (Viagra). nhs.uk
- Electronic Medicines Compendium. Viagra and generic sildenafil film-coated tablets: Summaries of Product Characteristics. medicines.org.uk
- Medicines and Healthcare products Regulatory Agency. Yellow Card scheme: report a suspected side effect or a fake medicine. yellowcard.mhra.gov.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Viagra and generic sildenafil tablets are prescription-only medicines (Viagra Connect 50mg is a pharmacy medicine), and they need a clinical or pharmacist assessment before they can be supplied. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.
Reporting side effects: If you think a medicine has caused a side effect, you can report it to the MHRA through the Yellow Card scheme at yellowcard.mhra.gov.uk or the Yellow Card app. You can also report suspected fake or unlicensed medicines. Reporting helps keep medicines safe for everyone in the UK.