The Independent Pharmacy

Sildenafil Side Effects: A Complete Guide

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 6 Apr 2023

Sildenafil, whether sold generically or under the Viagra brand, is the most famous erectile dysfunction tablet in history — in many ways, it’s responsible for an entire industry. Above all else, that’s an indication of how safe it is to use. Millions of people around the world have used it and ultimately be satisfied with its effects.

But every treatment, no matter how safe, has the potential for side effects. Sildenafil has some mild side effects that are reasonably common, and others that are more serious but occur rarely. On this page, we’ll explain what using Sildenafil is supposed to be like, cover the possible side effects, and make clear how you can use it safely.

What using Sildenafil should feel like

Sildenafil functions by helping blood vessels to dilate, improving blood flow and lowering blood pressure (the heart doesn’t need to pump as hard to circulate blood). Once it takes effect (which will generally be within 30 - 60 minutes of taking it), you should feel the increase in blood flow — you might become slightly light-headed or flushed as a result.

Aside from that, using Sildenafil doesn’t provide a particular experience in itself. It’s a facilitator. While it’s in effect (which will be for 4-6 hours at full potency — there’s more detail on our page about how long Sildenafil lasts), you should find it significantly easier to achieve and maintain an erection. If you generally suffer from poor circulation, you may also find it alleviated as a byproduct. Any other positive effects are coincidental — if you feel more aroused, it will likely be due to your thoughts and feelings about your performance (as opposed to the drug itself).

Sildenafil Tablets (25mg, 50mg & 100mg)
Sildenafil Tablets (25mg, 50mg & 100mg)
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The most common Sildenafil side effects

Let’s start with a quick summary of the most common Sildenafil side effects:

  • Mild to moderate headaches
  • Nausea
  • Dizziness
  • Flushing (hot, reddened skin)
  • Indigestion
  • Blurred/tinged vision
  • Nasal blockage

Of these, developing a headache is the most common, affecting as many as (or more than) 1 in every 10 users. The others are a little less common, but still somewhat frequent. Note that every one of these side effects is almost certainly temporary — if it doesn’t go away while the Sildenafil is in effect, it will disappear when it stops working.

Rarer Sildenafil side effects

Other side effects of Sildenafil that occur significantly less frequently (affecting fewer than 1 in 100 people) include the following:

  • Vomiting
  • Fatigue
  • Vertigo
  • Skin rashes
  • Irritated/bloodshot eyes
  • Disrupted vision (sensitivity, flashes of light, even pain)
  • Rapid heart rates
  • Extreme blood pressure (high or low)
  • Nosebleeds
  • Muscle pain
  • Mouth dryness
  • Reduced nerve sensitivity
  • Tinnitus
  • Nose/sinus blockages
  • Chest/limb pain
  • Heartburn

The most uncommon side effects of Sildenafil

Very rarely, affecting fewer than 1 in every 1000 users, Sildenafil can produce side effects including the following:

  • Fainting spells
  • Strokes
  • Heart attacks
  • Heartbeat arrhythmia
  • Decreased brain blood flow
  • Eye bleeding and/or swelling
  • Penile bleeding (possibly blood in semen)
  • Sudden loss of hearing

Other side effects (typically to do with the heart) are occasionally reported, but without any confirmation about the circumstances, there’s no way to know what role Sildenafil actually plays in them. For instance, people with heart conditions sometimes acquire it and use it despite doctors recommending otherwise, with dangerous consequences.

How likely are you to experience side effects?

Crowd of people showing the chances of Sildenafil side effects

Since the most common side effects of Sildenafil don’t affect more than 1 in 10 users, and countless people throughout the world have had great success using it on a regular basis, it’s clear that experiencing side effects — at least, those that would cause sufficient discomfort or distress to affect sexual activity — is fairly unlikely.

If you follow the prescribed instructions to the letter, take the right dosages, and remain in good health, there’s an excellent chance that you’ll have nothing but positive things to say about your experiences using Sildenafil.

When you should seek medical assistance

Though the side effects of Sildenafil tend to be mild and brief, there are various circumstances in which things can go wrong to the extent that you should immediately seek out a medical expert to diagnose and assist you. Here’s when you need emergency support:

  • You’ve had an allergic reaction. If you find it difficult to breathe, become dizzy, see your skin blistering or peeling, or notice significant swelling in your face, features or throat, you may be allergic to one of the ingredients.
  • You’ve developed severe chest pain. Sexual activity stresses the heart, and if you have an underlying condition, it can cause problems. Try to calm down.
  • You’ve suffered a seizure. This is very uncommon but has been known to happen. If you seize up, call a doctor as soon as possible.
  • Your vision has been majorly impaired. If this happens, it’s likely to be temporary, but it’s still a huge cause for concern.
  • You’ve stayed erect for over 4 hours. When your level of arousal goes down, your erection should subside. If it doesn’t, and you stay erect for a long time, it can cause penile damage.

How to deal with the side effects of Sildenafil

In most cases, users of Sildenafil don’t need to do anything special to deal with side effects — they either don’t appear at all, or they’re mild enough to be ignored until they go away. However, if they threaten your health or make it undesirable to continue with sexual activity, you should stop what you’re doing and try to relax as much as possible.

If you experience a headache while using Sildenafil, you might want to take a painkiller to dull the pain, such as paracetamol or ibuprofen - provided you don't have any medical problems that would mean they aren't suitable for you.

Can it affect your health in the long term?

Various studies have been done on the effects of Sildenafil when used regularly for years, and the findings have suggested that it’s extremely safe. Most men who use it frequently can continue to do so indefinitely without seeing diminished returns or an increase in the appearance or severity of side effects.

The only notable negative long-term consequences involve users coming to rely upon Sildenafil to make up for diminished arousal or hurting themselves through engaging in vigorous sexual activity for extended periods. If you look after your health and wellbeing, you should be fine, as evidenced by the many great reviews (see more on our main Sildenafil reviews page).

Is Sildenafil worth risking side effects?

Since it’s fairly unusual for someone otherwise healthy (and following their prescription) to have a bad experience using Sildenafil, the answer is a clear yes. If it doesn’t work in your particular base for whatever reason (for example, your erectile dysfunction has some other cause such as anxiety or depression), then you can simply discontinue use and seek another solution.

Circumstances in which Sildenafil isn’t a good choice

Some men shouldn’t use Sildenafil — this can be due to other health conditions, other medical treatments they’re using, or the problem being unrelated to blood flow. If you believe your heart is in good shape and you’re not currently using other ED treatments, you’re likely to be eligible. Check with a medical expert to confirm.

For a comprehensive list of circumstances in which someone shouldn’t use Sildenafil, head to our main page about what Sildenafil is and how it works and find the appropriate section. It should be able to satisfy your curiosity — it also follows up with a section on alternatives to this treatment, so you do have options if it isn’t right for you.


Wrapping up, let’s review the main takeaways from this page:

  • Sildenafil produces side effects in around (or fewer than) 1 in 10 users
  • Most side effects are mild and temporary
  • Provided you’re healthy enough to use it, you should be fine
  • If it doesn’t work for you, there may be another explanation for your ED
  • If something goes significantly wrong, stop immediately and consult a doctor

Eager to get a prescription and give it a try? You can buy Sildenafil after completing a short online consultation with one of our registered medical team.


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