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How it works
Tadalafil works by increasing blood flow

into the erectile tissue of the penis,

allowing for a firm erection

The medicine

Tadalafil belongs to a class of medicines known as 'PDE-5 inhibitors'. It contains the same active ingredient as the branded ED medicine Cialis.  Tadalafil comes in 10mg and 20mg doses.

How to take it

  • Take one tablet one hour before sex.  

  • Tadalafil usually starts working within one hour and positive effects can last for up to 36 hours.

  • Drinking more than one or two units of alcohol with Tadalafil will limit its effectiveness.

  • Tadalafil can be taken with or without food.

  • You should not take more than one tablet within a 36-hour period.

How it works

Tadalafil works by increasing blood flow into the erectile tissue of the penis, allowing for a firm erection. Tadalafil is not an aphrodisiac and does not improve your sexual desire; you need to be sexually aroused for the medication to work.


Tadalafil works for up to 80% of men and remains effective for up to 36 hours. The majority of men will notice a firmer and longer lasting erection after taking this medicine.

The medicine’s effectiveness depends on the cause and severity of the erectile dysfunction. Unlike Sildenafil or Viagra, taking this pill with food will not impact its effectiveness, although alcohol may reduce its effects.

If Tadalafil doesn’t work for you first time around, it could nevertheless be more effective next time. We advise trying all erectile dysfunction medicines eight times before switching to an alternative or increased dose.

Side effects

Most patients experience no side effects from this medication. However possible side effects include headaches, indigestion, light headedness, facial flushing, nasal congestion and muscle aches. These side effects should not last more than a few hours after taking a dose of Tadalafil.

There can be more severe side effects, though these are rare. You should refer to the manufacturer leaflet that comes with the medication for a full list of side effects.

Taking other medicines with Tadalafil

Tadalafil interacts with certain medicines such as nicorandil and those containing nitrates like GTN sprays and isosorbide mononitrate. Tadalafil also interacts with alpha blockers like tamsulosin and doxazosin.

Our clinicians will not be able to prescribe tadalafil if you are taking alpha-blockers, nicorandil or nitrates, such as GTN spray or isosorbide mononitrate tablets.

It is important that you tell us about all the medicines you are currently taking so we can safely prescribe you a suitable treatment.

Alternative treatments

Erectile dysfunction can be a sign of an underlying medical condition such as diabetes, high blood pressure, high cholesterol and hormonal conditions. It is important that you see your GP for tests for these conditions, as they increase your risk of heart disease or stroke.

Some men find counselling helpful as a means of exploring psychological causes for ED. If you wish to try counselling, then some sexual health clinics (also known as GUM clinics) offer this service, and your GP will also be able to direct you to your local services.

If Tadalafil does not work for you,  we can discuss your treatment options. We can also prescribe the following ED treatments: