Short answer: For daily Cialis, the Patient Information says that if you miss a dose, you may take it when you remember, but do not take more than one dose per day. Daily Cialis is 2.5 mg or 5 mg at about the same time each day. Tadalafil has a half-life of about 17.5 hours.
| Situation | What the label says |
|---|---|
| Daily schedule | 2.5 or 5 mg at about the same time every day (2.2 to 2.4) |
| Missed a daily dose | May take it when you remember (Patient Information) |
| Most per day | One dose (Patient Information; 2.1) |
| As-needed use | At most once a day (2.1) |
| Half-life | About 17.5 hours (12.3) |
The Patient Information for daily Cialis (for erectile dysfunction, BPH, or both) says: if you miss a dose, you may take it when you remember, but do not take more than one dose per day.
Example: you take 5 mg every morning and remember at 9 p.m. Under the label you may take it then. If you only remember the next morning, take your one dose for that day, not two.
As-needed Cialis is not on a schedule, so there is no dose to miss. Section 2.1 says the most it should be taken is once per day in most patients, and that it was shown to work up to 36 hours after a dose.
Tadalafil has a mean terminal half-life of about 17.5 hours in healthy adults (section 12.3). On a daily schedule, levels build up, so one missed tablet leaves some drug in your system.
The label says not to take Cialis with nitrates, and to be careful with alpha-blockers, blood pressure medicines and alcohol (sections 4.1, 5.6, 5.9). A late dose does not change any of that.
This page summarizes FDA labeling. It is not personalized medical advice; confirm what to do with your prescriber or pharmacist.