How long does Cialis last?

A single on-demand dose (10 mg or 20 mg) can remain effective for up to 36 hours. This is markedly longer than sildenafil (Viagra), which typically lasts 4 to 6 hours, and is why Cialis is sometimes called the 'weekend pill'. Only one on-demand dose should be taken in any 24-hour period.

What is the difference between Cialis on demand and Cialis daily?

On-demand Cialis (10 mg or 20 mg) is taken 30 minutes before anticipated sexual activity and works for up to 36 hours. Daily Cialis (2.5 mg or 5 mg) is taken every day at the same time, keeping a steady low level of tadalafil in the bloodstream. Daily dosing suits men who prefer spontaneity or who have sexual activity more than twice a week.

What should I do if I miss a dose?

On-demand Cialis is taken only when needed before activity, so there is no regular schedule to miss. If you forget, take it when you remember before anticipated activity, and never take two doses within 24 hours. For daily Cialis, take the forgotten dose when you remember, unless it is nearly time for the next dose, in which case skip it. Never take a double dose to make up for a missed one.

Is Cialis affected by food or alcohol?

Unlike sildenafil, tadalafil absorption is not significantly affected by food, including high-fat meals. Moderate alcohol (up to around 3 units) does not meaningfully reduce effectiveness, but excessive alcohol can worsen erectile dysfunction and increase side effects such as low blood pressure, dizziness, and headache.

When is Cialis preferred over Viagra?

Cialis is often considered when a longer window of effect (up to 36 hours) or a once-daily continuous option is wanted, and it is the only PDE5 inhibitor also approved for BPH. Viagra (sildenafil) may be preferred when a shorter, planned effect is acceptable, when food interactions are manageable, or when cost is the main concern, as generic sildenafil is typically less expensive.

Can I get Cialis online in Europe?

You can access Cialis through online intermediary platforms that connect you with independent EU-registered doctors. After completing a confidential health assessment, a doctor decides whether tadalafil is clinically appropriate. Prescrivia does not prescribe or dispense medicines, employ doctors, or guarantee that a prescription will be issued.

Cialis (Tadalafil): Uses, Dosage, and Side Effects

Summary: Cialis is the brand name for tadalafil, a prescription-only medicine authorised across the EU by the European Medicines Agency (EMA) for the treatment of erectile dysfunction (ED) in adult men (EMA product number EMEA/H/C/000436, holder Eli Lilly Nederland B.V.). It belongs to the same class as sildenafil (Viagra) — phosphodiesterase type 5 (PDE5) inhibitors — but stands out for its long duration of action (up to 36 hours) and its availability as a once-daily tablet.

1. What is Cialis used for?

Approved medical uses

Cialis (tadalafil) is EMA-authorised for:

Erectile dysfunction (ED) in adult men — the persistent difficulty achieving or maintaining an erection sufficient for satisfactory sexual activity.
Benign prostatic hyperplasia (BPH) — the 5 mg once-daily dose is authorised for the signs and symptoms of an enlarged prostate (urinary hesitancy, weak stream, incomplete emptying, nocturia).
Combined ED and BPH — the 5 mg once-daily dose is authorised for men who have both conditions.

Sexual stimulation is required for tadalafil to produce an erection. Cialis is not authorised for use by women or by anyone under 18.

Common off-label uses (not authorised by the EMA for the Cialis brand)

These uses are reported in clinical literature but are not authorised for the Cialis brand in the EU. They are listed for completeness only and should not be attempted without a doctor’s assessment:

Pulmonary arterial hypertension (PAH): Tadalafil is authorised for PAH, but under the separate brand Adcirca, not Cialis.
Raynaud’s phenomenon and altitude-related symptoms: Sometimes studied off-label; not authorised.
Adjunct use in premature ejaculation or lower urinary tract symptoms not linked to BPH: Not authorised for Cialis.

2. How to take Cialis

Standard dosage and administration

Cialis is available as tablets (2.5 mg, 5 mg, 10 mg, and 20 mg) and is used in two distinct regimens. The exact dose must always be set by an independent doctor after reviewing your health assessment.

On-demand dosing (for sexual activity)

Strength	Typical use
10 mg	Standard starting dose, taken at least 30 minutes before sexual activity
20 mg	Maximum on-demand dose, used only if 10 mg is well tolerated but insufficiently effective

Take no more than one on-demand dose in any 24-hour period. Effect can last up to 36 hours.

Daily dosing (continuous effect)

Strength	Typical use
2.5 mg once daily	Starting dose for the daily regimen
5 mg once daily	For ED, BPH, or both; used if 2.5 mg is insufficient

Take the daily dose at the same time each day, with or without food.

Timing and food

Take on-demand Cialis at least 30 minutes before anticipated sexual activity.
Cialis can be taken with or without food, including high-fat meals, with no clinically meaningful impact on absorption. This differs from sildenafil, whose onset is delayed by heavy meals.
Swallow tablets whole with water. Do not split or crush them.

What to do if you miss a dose

On-demand Cialis: Because it is taken only when needed, there is no schedule to miss. If you forget, simply take it when you remember before anticipated activity. Never take two doses within 24 hours.
Daily Cialis: Take the forgotten dose as soon as you remember, unless it is nearly time for your next dose, in which case skip the missed one. Do not take a double dose to make up for a missed one.

3. Side effects of Cialis

Not everyone experiences side effects. Most are mild and short-lived.

Common side effects (may affect more than 1 in 10 people)

Headache
Dyspepsia (indigestion, heartburn)
Back pain
Myalgia (muscle aches)
Flushing (facial warmth and redness)
Nasal congestion

Back pain and muscle aches are reported more often with tadalafil than with sildenafil or vardenafil and typically settle within 48 hours without treatment.

Less common side effects (may affect up to 1 in 10 people)

Dizziness
Blurred vision
Increased or altered heart rate (palpitations, tachycardia)
Low blood pressure
Abdominal pain or reflux
Increased sweating

Serious side effects — seek emergency care immediately

Emergency signs — stop taking Cialis and get medical help straight away:

Priapism: a persistent erection unrelated to sexual stimulation lasting more than 4 hours. This is a medical emergency that can cause permanent damage without urgent treatment.

Sudden vision loss in one or both eyes — a rare possible sign of non-arteritic anterior ischaemic optic neuropathy (NAION).

Sudden decrease or loss of hearing, sometimes with ringing in the ears and dizziness.

Severe allergic reaction: swelling of the face, lips, tongue, or throat, skin rash, or difficulty breathing.

Signs of a heart attack or stroke: chest pain, shortness of breath, weakness on one side, slurred speech, or fainting.

On the reported ocular risk: whether PDE5 inhibitors meaningfully increase the risk of conditions such as retinal vascular events or ischaemic optic neuropathy remains scientifically debated. A large insurance-database study of nearly two million men found no significant association with ocular events (Belladelli et al., 2023; PMID 37861186), while a separate cohort reported a higher rate of certain ocular events in regular users (Etminan et al., 2022; PMID 35389459). The EMA continues to list sudden vision loss as a possible rare effect that requires stopping the medicine and seeking urgent care.

This is not a complete list. Refer to the EMA-approved product information (SmPC and patient leaflet) for full details, and report suspected side effects to your national medicines authority.

4. Warnings and precautions

Who should avoid Cialis

Cialis must not be used by people who:

Take nitrates in any form (glyceryl trinitrate, isosorbide mononitrate, isosorbide dinitrate, or nitrate-containing recreational drugs such as amyl nitrite “poppers”) — the combination can cause a dangerous, potentially life-threatening drop in blood pressure.
Take the guanylate cyclase stimulator riociguat (used for pulmonary hypertension).
Have severe cardiovascular disease, or have been advised by a doctor to avoid sexual activity for cardiac reasons.
Have had a heart attack or stroke within the last 90 days (or as advised by the reviewing doctor).
Have blood pressure below 90/50 mmHg or uncontrolled high blood pressure.
Have severe liver impairment (Child–Pugh Class C).
Have a hereditary degenerative retinal disorder such as retinitis pigmentosa, or a history of NAION.

Special populations

Pregnancy and breastfeeding: Cialis is not authorised for women. No contraceptive or fetal-protection advice applies to its use in men; tell your doctor if your partner is pregnant or planning pregnancy.
Liver impairment: In mild to moderate liver impairment, the maximum on-demand dose is 10 mg and daily dosing is generally avoided. Cialis should not be used in severe liver impairment.
Kidney impairment: In moderate kidney impairment, the maximum on-demand dose is 10 mg no more than once every 48 hours, and daily dosing should start at 2.5 mg. Cialis is generally not recommended for daily use in severe kidney impairment.
Age limits: Cialis is not authorised for anyone under 18. No dose adjustment is required for healthy older men, but a doctor may start at the lower end depending on other health conditions and medications.
Heart conditions and alpha-blockers: If you take alpha-blockers (for high blood pressure or prostate symptoms), Cialis can be used with care, usually starting at the lowest dose, to reduce the risk of low blood pressure and fainting.

5. Drug and lifestyle interactions

Prescription and over-the-counter medicines

Nitrates and nitric oxide donors (any form): absolutely contraindicated.
Alpha-blockers (doxazosin, tamsulosin, alfuzosin, others): risk of low blood pressure and fainting; doses should be staggered and a doctor should set the starting dose.
Other blood-pressure-lowering medicines: effect may add up; monitoring may be needed.
CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir, clarithromycin, grapefruit-containing medicines): can raise tadalafil levels and increase side effects; a doctor may reduce the maximum dose.
CYP3A4 inducers (rifampicin, certain anti-epileptics): can lower tadalafil levels and reduce effectiveness.
Riociguat: contraindicated.
Other PDE5 inhibitors: do not combine Cialis with Viagra, Levitra, or any other ED medicine.

Alcohol and diet

Alcohol: keep to moderate intake. Heavy drinking can lower blood pressure, worsen erectile dysfunction, and increase side effects such as dizziness and headache.
Grapefruit and grapefruit juice: may raise tadalafil levels. Limit intake and check with your doctor, especially if you also take interacting medicines.
Food: high-fat meals do not meaningfully affect Cialis absorption.

Supplements and herbal products

St John’s wort: may reduce tadalafil levels by inducing CYP3A4.
L-arginine and nitric-oxide-style supplements: may add to blood-pressure-lowering effects; use only with a doctor’s advice.
Yohimbine: may increase heart rate and blood pressure changes; not recommended in combination.

Always tell the reviewing doctor about every medicine, supplement, and recreational substance you use.

6. Cialis vs Viagra: how do they compare?

Both Cialis (tadalafil) and Viagra (sildenafil) are EMA-authorised PDE5 inhibitors for erectile dysfunction, available across the EU. Cialis is held by Eli Lilly Nederland B.V. (EMEA/H/C/000436); Viagra is held by Upjohn EESV (EMEA/H/C/000202). The table is for information only — a doctor must decide which, if either, is clinically appropriate for you.

Feature	Cialis (tadalafil)	Viagra (sildenafil)
Active ingredient	Tadalafil	Sildenafil (as sildenafil citrate)
Primary use	Erectile dysfunction; also authorised for BPH	Erectile dysfunction
Speed of onset	~30 minutes	~30 to 60 minutes
Duration of effect	Up to 36 hours	4 to 6 hours
Dosing options	On-demand (10–20 mg) or once-daily (2.5–5 mg)	On-demand only (25–100 mg)
Effect of food	Minimal; high-fat meals do not significantly affect it	Onset delayed by heavy or high-fat meals
Common side effects	Headache, indigestion, back pain, muscle aches, flushing, nasal congestion	Headache, flushing, indigestion, nasal congestion, temporary blue-tinted vision
Nitrates	Absolutely contraindicated	Absolutely contraindicated
When preferred	When a long window or daily option is wanted, or when BPH is also present	When a shorter planned effect is acceptable or cost is the main concern (generic sildenafil is typically cheaper)

When might a doctor prefer Cialis?

Independent network meta-analyses consistently rank sildenafil and tadalafil among the most effective on-demand PDE5 inhibitors for improving erectile function, with sildenafil showing the strongest effect size and tadalafil a comparable and durable response (Salonia et al., 2026; PMID 42296271).

A doctor may consider Cialis when a longer, more flexible window of effect is wanted, when a man prefers not to time tablet-taking around sexual activity (using the daily regimen), or when enlarged prostate symptoms are also present, because tadalafil is the only PDE5 inhibitor authorised for BPH. Cialis’s absorption is not slowed by food, which some people find more convenient.

When might a doctor prefer Viagra?

A doctor may consider Viagra (or lower-cost generic sildenafil) when a shorter, planned effect is acceptable, when the longer exposure of tadalafil is not wanted, or when cost is the main concern, as generic sildenafil is generally less expensive. Sildenafil also has the longest post-market record of any PDE5 inhibitor, having been authorised in the EU in 1998.

What neither medicine does

Neither Cialis nor Viagra cures erectile dysfunction, increases sexual desire, protects against sexually transmitted infections, or produces an erection without sexual stimulation. ED can be an early sign of cardiovascular disease, diabetes, or other underlying conditions, so a doctor’s assessment — not self-selection — should guide any treatment.

How to access Cialis online in Europe

Cialis is a prescription-only medicine (POM) in all EU member states. A valid prescription from a licensed medical professional is required before it can be legally dispensed.

Prescrivia operates as a technology intermediary: we do not prescribe medicines, employ doctors, or sell medicines. Our platform connects patients with independent EU-registered doctors who carry out confidential online health assessments, and with licensed EU pharmacy partners for fulfilment.

The process works as follows:

Complete a health assessment. Answer structured questions covering your medical history, current medications, urinary symptoms, and relevant lifestyle factors.
Doctor review. An independent EU-registered doctor reviews your assessment. If tadalafil is clinically appropriate — on-demand or daily — they may issue a prescription. If it is not appropriate, the doctor explains why.
Prescription and fulfilment. If a prescription is issued, it is sent to a licensed EU pharmacy partner, which dispenses and ships the medicine to you.

Important: Prescrivia does not guarantee that a prescription will be issued. All prescribing decisions are made independently by qualified medical professionals based on individual clinical circumstances.

Sources

Medical information on this page is based on the following sources.

Regulatory (primary sources)

European Medicines Agency (EMA). Cialis (tadalafil) — Summary of Product Characteristics (SmPC) and Summary of the EPAR. Product number EMEA/H/C/000436. Available at: ema.europa.eu
European Medicines Agency (EMA). Viagra (sildenafil) — Summary of Product Characteristics (SmPC) and Summary of the EPAR. Product number EMEA/H/C/000202. Available at: ema.europa.eu
European Medicines Agency (EMA). Safety-related referrals register (no active referral affecting tadalafil or sildenafil as of the review date).

Peer-reviewed evidence (PubMed-indexed)

Salonia A, et al. A comparative evaluation of on-demand phosphodiesterase-5 inhibitor efficacy in erectile dysfunction: systematic review and network meta-analysis of double-blind, placebo-controlled, randomised trials. The Journal of Sexual Medicine. 2026. PMID: 42296271.
Kim M, Noh Y, Yamada A, Hong SH. Comparison of the erectile dysfunction drugs sildenafil and tadalafil using patient medication reviews: topic modeling study. JMIR Medical Informatics. 2022. PMID: 35225813.
Belladelli F, et al. Use of phosphodiesterase 5 inhibitors is not associated with ocular adverse events. The Journal of Sexual Medicine. 2023. PMID: 37861186.
Etminan M, et al. Risk of ocular adverse events associated with use of phosphodiesterase 5 inhibitors in men in the US. JAMA Ophthalmology. 2022. PMID: 35389459.
Sridharan K, Sivaramakrishnan G. Hypotensive events associated with PDE-5 inhibitors in pulmonary arterial hypertension: assessment of the USFDA Adverse Event Reporting System. Hospital Pharmacy. 2026. PMID: 42170200.

This content is reviewed periodically to reflect updated clinical guidance.

Disclaimer: Prescrivia is a technology platform connecting patients with independent EU-registered doctors and licensed pharmacies. This article is for informational purposes only and does not constitute medical advice. Always consult an independent healthcare professional before starting or changing any treatment.

Cialis (Tadalafil)

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