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 at least 30 minutes before anticipated sexual activity and works for up to 36 hours. Daily ED treatment starts at 5 mg once daily and may be reduced to 2.5 mg for tolerability; BPH or ED with BPH uses 5 mg once daily. 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. Alcohol can worsen erectile dysfunction and contribute to low blood pressure, dizziness and headache. The label does not establish a universally safe intake.

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.

How does an online assessment for Cialis work?

You can access Cialis through online intermediary platforms that connect you with independent 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) vs Viagra: Uses, Dosage, Side Effects

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.

Product and indication boundaries

Other tadalafil products can have different indications. This Cialis article does not provide a regimen for pulmonary arterial hypertension, Raynaud’s phenomenon, altitude symptoms or premature ejaculation.

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
5 mg once daily	Recommended daily ED dose; also the daily dose for BPH or ED with BPH
2.5 mg once daily	Reduction for ED based on tolerability; not the BPH regimen

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

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

Back pain and muscle aches can occur; persistent or troublesome symptoms need medical advice.

Uncommon side effects

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

Rare side effects

Increased sweating

Serious side effects — seek emergency care immediately

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

Priapism: an erection lasting 4 hours or more. 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.

Vision warning: Current product information includes NAION and central serous chorioretinopathy (CSCR). Stop Cialis and consult a doctor immediately for sudden visual defects, reduced visual acuity or visual distortion. Conflicting observational studies do not cancel this warning.

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 within 90 days, or a stroke within 6 months.
Have unstable angina, angina during sex, NYHA class 2 or greater heart failure within 6 months, or uncontrolled arrhythmias.
Have blood pressure below 90/50 mmHg or uncontrolled high blood pressure.
Have lost vision in one eye due to NAION, whether or not related to previous PDE5 inhibitor use.
Are allergic to tadalafil or any excipient.

Special populations

Use in men: Cialis is not indicated for women or children.
Liver impairment: On-demand dosing is 10 mg; doses above this have not been studied. Severe impairment (Child-Pugh C) has limited safety data and requires a careful individual benefit/risk assessment if prescribed. Daily use has not been evaluated in hepatic impairment and also requires that assessment.
Kidney impairment: No adjustment is required for mild–moderate impairment. Severe impairment: maximum 10 mg on demand; daily use is not recommended.
Age: No adjustment is required solely for older age.
Alpha-blockers: Concomitant use may cause hypotension; the combination with doxazosin is not recommended. Other alpha-blockers require care.
Other precautions: Penile deformity, sickle cell anaemia, myeloma or leukaemia can increase priapism risk. Disclose retinal disease. Cialis contains lactose; specified hereditary galactose/lactase/glucose-galactose disorders preclude use.

5. Drug and lifestyle interactions

Prescription and over-the-counter medicines

Nitrates and nitric oxide donors (any form): absolutely contraindicated.
Alpha-blockers: The combination with doxazosin is not recommended; other combinations need caution because of hypotension and fainting. Do not change another medicine yourself.
Other blood-pressure-lowering medicines: effect may add up; monitoring may be needed.
CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir, clarithromycin): 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.

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, authorised in the EU; authorisation does not prove current supply. 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
Examples of side effects (frequency differs by product)	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?

Treatment choice should follow individual assessment; an efficacy ranking alone does not establish suitability.

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.

Online assessment for Cialis (Tadalafil)

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 doctors who carry out confidential online health assessments, and with 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 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 pharmacy partner, which is responsible for dispensing under applicable national rules; delivery and stock are not established by this article.

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.

In Spain, distance sale of prescription medicines is prohibited under Article 3.5 of Royal Legislative Decree 1/2015. An online assessment does not remove this restriction. Dispensing and access depend on the exact product and applicable national rules.

Sources

Current label warnings take precedence over unsupported comparative reassurance. This editorial update is not a new clinical review.

Disclaimer: Prescrivia is a technology platform connecting patients with independent 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)

Assessment availability

Strengths and types