Checked against the current FDA label, named clinical trials, and the sources listed on this site.
01Once per day after a 20 mg tablet
As-needed Cialis for ED starts at 10 mg taken prior to anticipated sexual activity. The as-needed dose may be 20 mg based on individual efficacy and tolerability. A 5 mg as-needed tablet may be used when a lower dose is needed. In most patients the maximum dosing frequency is once per day.
02Food does not change absorption
The rate and extent of absorption of tadalafil are not influenced by food. Cialis may be taken with or without food.
A high-fat meal had no clinically relevant effect on rate or extent. Food-effect comparisons used 90 percent confidence intervals for Cmax and AUC mean ratios. The food-effect work used a 20 mg dose.
03Thirty-six hours versus placebo
As-needed Cialis improved erectile function compared with placebo up to 36 hours after dosing. In two studies, men were assigned to attempt intercourse at 24 hours after the dose or at 36 hours after the dose.
Both assigned times still beat placebo. The endpoint was successful intercourse after a single as-needed dose. Mean terminal half-life in healthy subjects is 17.5 hours.
04Nitrates stay off for 48 hours
If a nitrate is needed in a life-threatening situation after Cialis, at least 48 hours should have elapsed after the last dose. The nitrate is given under close medical supervision with hemodynamic monitoring. The blood-pressure effect was still present at 24 hours. By most hemodynamic measures it was not detectable after 48 hours.
Sources and how this letter was sealed
FDA / Lilly, Cialis (tadalafil) US prescribing information: as-needed 10 mg start, 20 mg step, 36-hour efficacy language, t½ 17.5 h, food without regard, 48-hour nitrate wait.
Method in brief: open primary sources, annotate against the current FDA label,
countersign by Dr. Nora Lindqvist, MD, then seal with a dated review.
Full walk-through on the method page and
editorial standards.
How to cite this page - Vancouver style
Juvia Pharma Drug Reference. How far one 20 mg tadalafil tablet is measured [Internet]. Stockholm: Juvia Pharma; 21 October 2026 [cited 2026 Aug 21]. Available from: https://juviapharma.com/postscripts/tadalafil-weekend-window/
Desk thread
Answers follow the U.S. Cialis prescribing information.
Pia Holmqvist, Kalmar writes
I took 20 mg Friday at 21:00. Can I take another 20 mg Saturday at noon?
Desk reply
As-needed Cialis for ED starts at 10 mg taken prior to anticipated sexual activity. The as-needed dose may be 20 mg based on individual efficacy and tolerability. A 5 mg as-needed tablet may be used when a lower dose is needed. In most patients the maximum dosing frequency is once per day.
Arvid Sten, Falun writes
Does 36 hours mean an erection lasts that long?
Desk reply
As-needed Cialis improved erectile function compared with placebo up to 36 hours after dosing. In two studies, men were assigned to attempt intercourse at 24 hours after the dose or at 36 hours after the dose. Both assigned times still beat placebo. The endpoint was successful intercourse after a single as-needed dose. Mean terminal half-life in healthy subjects is 17.5 hours.
Tuva Berglund, Ostersund writes
Can I swallow the 20 mg tablet with dinner?
Desk reply
The rate and extent of absorption of tadalafil are not influenced by food. Cialis may be taken with or without food. A high-fat meal had no clinically relevant effect on rate or extent. Food-effect comparisons used 90 percent confidence intervals for Cmax and AUC mean ratios. The food-effect work used a 20 mg dose.
Henning Dahl, Kristiansand writes
I have a nitroglycerin spray. Is Saturday still open after Friday 20 mg?
Desk reply
If a nitrate is needed in a life-threatening situation after Cialis, at least 48 hours should have elapsed after the last dose. The nitrate is given under close medical supervision with hemodynamic monitoring. The blood-pressure effect was still present at 24 hours. By most hemodynamic measures it was not detectable after 48 hours.
Before you start, stop, or change any medicine mentioned above, run it past your prescriber or pharmacist - they hold your chart, this despatch does not. Desk notice.
