Sildenafil is the active ingredient in Viagra. We supply sildenafil tablets in 25mg, 50mg, 100mg after a consultation reviewed by a GPhC-registered pharmacist, and Viagra Connect (sildenafil 50mg) after a pharmacist consultation.
This guide explains when to take it, how long it lasts, and what can get in its way. The pharmacist decides whether sildenafil and a dose are right for you.
How long does sildenafil take to work?
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 can delay how quickly it works. These tablets only work with sexual stimulation. Without arousal there is no signal for the tablet to act on, so taking it and waiting is not enough on its own.
How long does sildenafil last?
Sildenafil is short acting: the product information for Viagra Connect, which is sildenafil 50mg, says it was effective at times from less than 1 hour to up to 4 hours after a dose. Its leaflet says you may take it up to 4 hours before sex.
It does not keep you erect for those hours. During that time it helps only when you are sexually aroused. An erection that will not go down after more than 4 hours is a medical emergency: see the safety box below.
Does food affect sildenafil?
Yes. A heavy or high-fat meal can delay how quickly it works. The NHS says you can otherwise eat as normal. If you have had a large meal, allow a little longer before you expect it to work.
Sildenafil: avoid grapefruit and grapefruit juice. Grapefruit can raise the amount of sildenafil in your blood and make side effects more likely.
Can I drink alcohol with sildenafil?
Keep it light. The NHS advises avoiding drinking too much alcohol while taking sildenafil, because it can make getting an erection more difficult. Drinking less alcohol can help your erections.
How often can I take sildenafil?
Once a day at most. Never take more than one tablet in 24 hours. That holds even if the first tablet did not help. Take it only when you need it, not every day.
There is also a limit on how much we can supply: maximum 8 tablets per 2 weeks.
What if sildenafil does not work?
Give it a few tries before you decide. Try a tablet 4 to 8 times before deciding it does not work, then tell us.
Before then, check the things that commonly get in its way:
- Arousal. These tablets only work with sexual stimulation.
- Timing. Take it about 1 hour before sex (anywhere from 30 minutes to 2 hours before). It takes about an hour to work.
- Food. A heavy or high-fat meal can delay how quickly it works.
- Alcohol. Drinking less alcohol can help your erections.
When you reorder, we ask how your last tablets worked and whether you had any side effects. If your dose did not work well enough and caused no side effects, the pharmacist can consider the next strength up. If a medicine has not worked after 4 to 8 tries at the highest dose that suits you, your pharmacist may suggest trying a different one.
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.
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 automatically.
Start your consultationHow does sildenafil compare with tadalafil?
The main difference is how long each one lasts. Tadalafil takes about 30 to 45 minutes to work, and its effect can last more than 24 hours. Tadalafil is not affected by food.
For when to take each tablet, daily tadalafil, side effects and who should not take them, see sildenafil vs tadalafil.
Who should not take sildenafil?
Sildenafil is not suitable if any of these apply to you:
- Nitrates in any form, including nicorandil or amyl nitrite (poppers)
- Riociguat (Adempas), vericiguat (Verquvo) or another guanylate cyclase stimulator
- Stroke or heart attack in the last 6 months
- Unstable angina, or angina during intercourse
- A heart condition for which a doctor has told you to avoid sex or strenuous activity
- Very low blood pressure, below 90/50
These are not the only reasons. The consultation also asks about your other medicines, your eyes, your liver and kidneys, and stops if sildenafil would not be safe for you. Less common side effects are listed in the leaflet in your pack. Please read it before your first dose.
See all our erectile dysfunction treatments.