What are the side effects of Viagra?

Medically reviewed by
Dr Babak AshrafiLast reviewed: 15 Feb 2022
When you take Viagra there’s a chance you might experience some side effects. This is normal, although the majority of people who take Viagra will not experience any side effects.
Viagra is used in the treatment of erectile dysfunction (ED) and it contains the active ingredient sildenafil citrate. Sildenafil is a phosphodiesterase type 5 inhibitor (PDE5 inhibitor).
Viagra works by increasing the blood flow to your penis, allowing you to get or maintain an erection when sexually aroused. As it affects your blood vessels, taking Viagra can cause side effects that you feel in other parts of your body. A common side effect is dizziness, which can happen due to a drop in blood pressure when your blood vessels dilate.
Most side effects of Viagra are temporary and will pass within minutes to a few hours of taking it.

What are the common side effects of taking Viagra?
The common side effects of Viagra can affect up to 1 in 10 people. You’re likely to experience these side effects, but you may not have them at all. These common side effects should disappear within a few hours as your body gets used to the effects of Viagra.
The common side effects of Viagra include:
- headache
- dizziness or lightheadedness
- feeling sick
- hot flushes
- facial flushing
- indigestion
- some visual changes like blurred vision
- nasal congestion
If these side effects persist for more than a few hours, speak to your doctor.
What are the less common side effects of taking Viagra?
The less common side effects of Viagra can happen in up to 1 in 100 people. This means that if 200 people took Viagra, around 1 to 2 people will feel these side effects.
Less common side effects of Viagra include:
- being sick
- dry mouth
- fast heartbeat or pounding heartbeat
- changes in your blood pressure
- visual changes like light sensitivity or watery eyes
- feeling tired
- nosebleeds
Like common side effects, the less common side effects should resolve within a few hours. If these side effects persist or happen every time you take Viagra and interrupts being intimate, speak to your doctor. You may need an alternative erectile dysfunction medication.
Are there any long term side effects of taking Viagra?
While there are no long term side effects of taking Viagra, you might find that it stops working as it should. This could be due to many reasons, such as:
- changes to your current health, for example developing diabetes or heart disease
- gaining weight
- getting older, and the general breakdown of blood vessels or nerves in the genital area
- feeling stressed or anxious about sex
- drinking alcohol
- smoking
Your doctor can recommend an alternative to Viagra, such as Cialis (tadalafil), Spedra and Levitra. They’ll also need to have a look at your general state of health and any new medicines you might be taking.
What should you do if you get side effects?
If you get side effects after taking Viagra, you can wait for them to resolve. Viagra remains effective for up to 4 hours, so you can wait for your side effects to disappear before having sex.
You can treat some side effects yourself. If you get a headache, you can take over the counter paracetamol to relieve the pain. If you feel dizzy, drink some water and sit or lie down until the dizziness passes.
If you get any signs of an allergic reaction after taking Viagra, you must contact your emergency department immediately. These include:
- difficulty breathing
- facial swelling including eyelids, lips and throat
- rashes
- fainting
In very rare situations, you may experience:
- prolonged erection that lasts for more than 4 hours (also called priapism)
- a sudden loss of vision
- seizures
If you get any of these symptoms after taking Viagra, you need urgent medical attention. Leaving these symptoms untreated can lead to long term problems in your health.
If you experience chest pain after taking Viagra, relax as much as you can. This might mean taking a break from sex. You should not use nitrate medication to relieve the chest pain. This includes isosorbide mononitrate tablets or glyceryl trinitrate (GTN) spray.
Are there any other risks of taking Viagra?
The risks of taking Viagra are low as long as you take it as your doctor or pharmacist has advised you to do so. If you have any existing medical conditions, you should let your doctor know. Taking Viagra with some health conditions can make you feel worse. These include:
- a deformation of the penis
- heart problems
- sickle cell anaemia
- leukaemia
- multiple myeloma
- if you've had a recent heart attack or stroke
- liver or kidney problems
- low blood pressure
- loss of vision due to non-arteritic anterior ischaemic optic neuropathy (NAION)
Your doctor may prescribe you a lower dose of Viagra. A lower dose means you’ll have less chance of getting side effects but you should still get the benefit of Viagra.
You should not take Viagra if you are a woman or under 18 years old.
Can Viagra cause an erection that will not go away?
There is a very small risk of Viagra causing an erection that does not go away. This is also called priapism, or a prolonged erection. A prolonged erection can last for more than 4 hours and can be painful.
If you use Viagra according to how your doctor has advised, you should not get a prolonged erection. In fact, there’s been little evidence to show that Viagra causes a prolonged erection when used in appropriate doses. Most documented cases of a prolonged erection have occurred when a very high dose of Viagra was taken. That’s why it’s important to follow your doctor’s guidance when taking Viagra.
Taking Viagra with other medications
If you are taking other medications, you should check with your doctor or pharmacist whether you can take Viagra. Viagra can interact with other medications. This means Viagra can make other medications less effective.
Medications that can interact with Viagra are:
- protease inhibitors used in HIV treatment such as ritonavir
- alpha blockers like doxazosin
- high blood pressure treatment
- antibiotics like erythromycin or rifampicin
- antifungal medication like ketoconazole or itraconazole
- bosentan or riociguat, used to treat pulmonary arterial hypertension
- recreational drugs that contain amyl nitrites, also called ‘poppers’
If you take nitrates to treat chest pain (also called angina), you should not take them when using Viagra. This includes glyceryl trinitrate (GTN) spray. If you have chest pain after using Viagra, speak to a medical professional immediately.
Are there any alternatives to Viagra?
There are a few alternatives to Viagra. If you experience side effects when taking Viagra, you can try another type of erectile dysfunction medication. Most ED medications work in a similar way, but you may find that you have fewer or no side effects with one compared to another.
At ZAVA, we offer Cialis, Spedra and Levitra. If you do not want to take a tablet, you can discuss using Vitaros cream with your doctor.
You do not always need to take medication to treat erectile dysfunction. Lifestyle changes can be just as powerful as prescription medication. These changes include losing weight, taking up a regular form of exercise or stopping smoking.

Babak studied medicine at King’s College London and graduated in 2003, having also gained a bachelor’s degree in Physiology during his time there. He completed his general practice (GP) training in East London, where he worked for a number of years as a partner at a large inner-city GP practice. He completed the Royal College of GPs membership exam in 2007.
Meet our doctorsLast reviewed: 15 Feb 2022
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Viagra 50 mg film-coated tablets (PIL) [Nov 2021] [accessed Jan 2022]
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Priapism following oral sildenafil abuse (Medical Journal of India) [Feb 2005] [accessed Jan 2022]
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Sildenafil citrate–Associated priapism (Urology) [June 2000] [accessed Jan 2022]


