This guide explains what tadalafil is, how its long duration works, the difference between on-demand and daily dosing, the side effects and the nitrates contraindication. It is based on the UK Summary of Product Characteristics, the NHS and NICE, and is general information rather than personal advice.
What tadalafil is
Tadalafil is a PDE5 inhibitor licensed for erectile dysfunction in adult men, and the active substance in Cialis; it is also available as generic tadalafil 1. Like sildenafil, it supports the natural erection response, but its defining feature is how long it lasts 1.
A single on-demand dose can remain effective for up to about 36 hours, which is why it is sometimes called the 'weekend pill' 1. That long window allows more spontaneity, because sex does not have to be timed to a narrow period after the dose 1.
Tadalafil is also licensed, at a low daily dose, for benign prostatic hyperplasia (BPH), the urinary symptoms of an enlarged prostate, and the daily dose can treat ED and BPH together where both are present 12.
How it works and how long it lasts
Tadalafil blocks the PDE5 enzyme, supporting the blood-vessel relaxation that allows an erection during sexual arousal 1. As with all PDE5 inhibitors, it works only with stimulation and does not increase desire 1.
Its long duration comes from how slowly it is cleared from the body compared with sildenafil 1. That is the basis of the up-to-36-hour on-demand window, and also why a small amount taken every day can keep a steady level for spontaneity 1.
The trade-off of a longer-acting medicine is that side effects, if they occur, can also last longer 1. Understanding the duration helps you choose between on-demand and daily dosing with a prescriber 13.
On-demand dosing (10-20 mg)
For on-demand use, the usual dose is 10 mg taken before anticipated sexual activity, at least 30 minutes beforehand 1. Depending on effect and tolerability, a prescriber may increase it to 20 mg or reduce it to a lower dose 1.
Because the effect lasts up to about 36 hours, on-demand tadalafil does not need the tight timing that sildenafil does 1. It can be taken with or without food, and unlike sildenafil its onset is not significantly affected by food1.
On-demand use should not exceed once per day1. Our guides on tadalafil 10 mg and tadalafil 20 mg cover each strength 1.
Considering treatment for erectile dysfunction? You can start an assessment with a Cloud Pharmacy clinician, who will review your medical history and confirm whether treatment is appropriate.
Daily dosing (2.5-5 mg)
Tadalafil can also be taken as a low daily dose, usually 5 mg (or 2.5 mg), taken at the same time each day regardless of when sex is anticipated 1. This keeps a steady level in the body, so sex can be spontaneous rather than planned around a dose 1.
Daily dosing suits people who anticipate frequent activity, or who prefer not to plan, and it is also the form used for BPH, treating urinary symptoms and ED together where both are present 12. It takes a few days of daily dosing to reach full effect 1.
Whether on-demand or daily suits you is an individual decision based on frequency, preference and your health, made with a prescriber 13. Our guide on tadalafil 5 mg daily covers this 1.
Side effects
The most common side effects are headache, indigestion, back pain, muscle aches, flushing and nasal congestion1. Back and muscle pain are more characteristic of tadalafil than of sildenafil, and usually settle within a couple of days 1.
Because tadalafil is long-acting, side effects can last longer than with shorter-acting options 1. They are usually mild, but if they are troublesome a prescriber can review the dose or option 12.
Seek emergency care for an erection lasting more than four hours (priapism), or for sudden loss of vision or hearing 1. These are uncommon but need prompt action 12.
Nitrates and other key cautions
Tadalafil must never be combined with nitrates (such as GTN), nicorandil or 'poppers', because the combination can cause a dangerous drop in blood pressure; this is an absolute contraindication 1. Its long duration means this caution applies for longer after a dose 1.
Alpha-blockers need caution because of the blood-pressure-lowering effect, and some other medicines can raise tadalafil levels, so a prescriber needs your full medicine list 1. There are also heart-related situations where it should be avoided or used only on advice 1.
These cautions are why tadalafil is assessed before prescribing 12. Our guides on nitrates and alpha-blockers cover them in detail 1.
Choosing tadalafil, and getting it safely
Tadalafil suits people who value a long window and spontaneity, whether through an on-demand dose lasting up to 36 hours or a low daily dose 1. Whether it is right for you, and which dosing pattern, is a clinical decision based on your health, frequency and preference 13.
Get tadalafil only through a registered pharmacy after a proper assessment, since the MHRA warns that fake ED medicines are common online 42. The assessment also checks whether the ED needs further investigation 2.
If you think tadalafil might suit you, you can start an assessment with a clinician to confirm whether it is appropriate and which dosing pattern fits 12. Our guide comparing sildenafil and tadalafil helps you weigh the options 3.
On-demand or daily: which fits your life
The choice between on-demand and daily tadalafil is mostly about how often and how spontaneously you anticipate sex 13. On-demand suits less frequent or more planned activity, where a single dose lasting up to 36 hours covers a weekend or an occasion 1.
Daily dosing suits people who want spontaneity without thinking about timing, or who anticipate frequent activity, since a steady low dose means there is no need to plan around a tablet 1. It is also the route when treating an enlarged prostate alongside ED 12.
There are trade-offs: daily dosing means taking a tablet every day whether or not sex happens, while on-demand means remembering to take one in advance 1. Neither is better in the abstract; it depends on your pattern and preference 13.
A prescriber can help you weigh these, and the choice is not permanent; if one pattern does not suit, it can be revisited 12.
ED as a signal worth investigating
As with the other ED medicines, persistent ED can be an early signal of an underlying condition such as diabetes, high blood pressure or heart disease, because the blood-vessel health behind erections overlaps with general cardiovascular health 23.
Psychological factors, stress, sleep, alcohol and some medicines can also contribute, so tadalafil treating the symptom does not remove the value of understanding why the ED is happening 23. The NHS encourages seeing a clinician if ED keeps happening 2.
The long-acting convenience of tadalafil is appealing, but it is still worth pairing symptom relief with a proper look at the cause 23. An assessment covers both 2.
That way you get the practical benefit of a long-acting medicine and the reassurance that nothing important underneath is being missed 23.
Key safety points to remember
The safety essentials for tadalafil mirror the class, with one twist from its long duration 1. Never combine it with nitrates, nicorandil or 'poppers'; because tadalafil lasts up to about 36 hours, that caution applies for longer after a dose than with sildenafil 1.
Tell whoever prescribes it about all your medicines and conditions, since alpha-blockers and some other medicines interact, and certain heart conditions mean it should be avoided or used only on advice 12. The longer duration makes a full picture especially useful 1.
Know the red-flag symptoms: an erection lasting more than four hours, or sudden loss of vision or hearing, both need emergency care 1. Milder effects such as back pain, muscle aches and headache are common and usually settle within a day or two 1.
And obtain it only from a registered pharmacy after a proper assessment, since the MHRA warns fake ED medicines are widespread online 42. Used within these rules, tadalafil's long-acting convenience can be enjoyed safely 1.
The long duration is genuinely useful, but it is also the reason to be a little more thoughtful about interactions and side effects, since both persist longer 1. Used correctly and reviewed by a prescriber, tadalafil offers a flexible, well-established option for ED, with the bonus of treating an enlarged prostate where both are present 12. As with any ED medicine, needing it is common and nothing to feel awkward about, and a confidential assessment is a routine part of getting it safely 23. For the right person, it is a flexible and convenient choice, and the assessment is there to make sure it is the right one 12.
Frequently asked questions
How long does tadalafil last?
A single on-demand dose can remain effective for up to about 36 hours, which is why it is called the 'weekend pill' 1. A low daily dose keeps a steady level for spontaneity 1.What's the difference between on-demand and daily tadalafil?
On-demand (usually 10 mg, up to 20 mg) is taken before sex; daily (2.5-5 mg) is taken at the same time each day for spontaneity, and is also used for BPH 1. Which suits you is a decision with a prescriber 13.Does food affect tadalafil?
Unlike sildenafil, tadalafil's onset is not significantly affected by food, so it can be taken with or without a meal 1. On-demand use should not exceed once per day 1.Can I take tadalafil with nitrates?
No, never. Combining tadalafil with nitrates, nicorandil or 'poppers' can dangerously lower blood pressure and is an absolute contraindication, and its long duration extends this caution 1. Tell your prescriber all your medicines 1.What are tadalafil's common side effects?
Headache, indigestion, back pain, muscle aches, flushing and nasal congestion, with back and muscle pain more typical of tadalafil 1. Seek emergency care for an erection over four hours or sudden vision or hearing loss 1.Can tadalafil treat an enlarged prostate too?
Yes. A low daily dose of tadalafil is also licensed for the urinary symptoms of benign prostatic hyperplasia, and can treat ED and BPH together where both are present 12.Your next step
Tadalafil is the long-acting PDE5 inhibitor for erectile dysfunction, the active ingredient in Cialis, with an on-demand dose lasting up to about 36 hours. It can be used on demand (usually 10 mg, up to 20 mg, taken at least 30 minutes before sex and not affected much by food) or as a low daily dose (2.5-5 mg) for spontaneity, which is also the form used for an enlarged prostate. It works only with stimulation, must never be combined with nitrates, and common side effects such as headache, indigestion and back pain are usually mild but can last longer because the medicine is long-acting.
Whether tadalafil suits you, and which dosing pattern, is a clinical decision based on your health, how often you anticipate sex and your preference. Get it only through a registered pharmacy after a proper assessment, since the MHRA warns that fake ED medicines are common. If you think tadalafil might suit you, you can start an assessment with a Cloud Pharmacy clinician to confirm whether it is appropriate and which dosing pattern fits.
Disclaimer
This guide is for general information only and does not constitute medical advice, diagnosis or treatment. The information here describes general clinical context based on UK regulatory sources cited above; it is not a recommendation for any specific medicine or treatment, which can only be made by a prescriber following individual assessment.
If you are considering treatment, speak to your GP or pharmacist, or arrange a consultation with a Cloud Pharmacy clinician. Prescription-only medicines are issued only after clinical assessment and where appropriate.
If you experience side effects from any medicine, you can report them through the Yellow Card scheme at yellowcard.mhra.gov.uk.
References
- Cialis (tadalafil) SmPC 4.1/4.2/4.3/4.4/4.5/4.8/5.1/5.2 (PDE5 inhibitor for ED and BPH; on-demand 10 mg, up to 20 mg, >=30 min before sex; daily 2.5-5 mg; up to ~36-hour duration; works only with stimulation; food not significant; common side effects incl. back/muscle pain; nitrates absolute contraindication; alpha-blocker/CYP3A4 cautions; priapism >4h, vision/hearing loss)
- Tadalafil (how used; daily and on-demand; BPH; assessment; ED can signal underlying conditions)
- NICE CKS erectile dysfunction (PDE5 inhibitor class; choosing between agents; assessment)
- MHRA #FakeMeds (fake ED medicines common online; buy only from registered pharmacies)
