How long does tadalafil last? Half-life and the label's timing window

Status: FDA-approved prescription medicine for ED. Source: Cialis prescribing information (Eli Lilly), DailyMed, checked 2026-10-17.

In short: tadalafil, sold as Cialis and as generics, is the long-acting pill in its class. The FDA label reports that a single as-needed dose improved erectile function compared with placebo for up to 36 hours, and that the drug’s mean half-life is 17.5 hours in healthy volunteers (Cialis prescribing information, DailyMed). Sildenafil’s half-life is about 4 hours by comparison (Viagra prescribing information, DailyMed). Food does not change how tadalafil is absorbed. Evidence level: approved drug, labeled use, timing figures from the label’s pharmacology section and placebo-controlled trials.

Sources: Cialis and Viagra prescribing information, DailyMed. Our page on how long sildenafil lasts covers the other column in detail.

How long does tadalafil last?

Tadalafil can help with erections for up to 36 hours after a single as-needed dose. That figure comes from the Cialis label, which states the drug “was shown to improve erectile function compared to placebo up to 36 hours following dosing” (Cialis prescribing information, DailyMed). This is a window in which the drug can help when arousal happens, not 36 hours of erection.

The window was tested directly. In a randomized trial of 348 men with ED (mean age 57), men were asked to attempt intercourse about 24 or 36 hours after a dose. At 36 hours, 59.2% of attempts were successful (completed, by the men’s own diary reports) on tadalafil against 28.3% on placebo; at about 24 hours the figures were 52.9% and 29.1% (Porst et al., Urology 2003). Those are group averages, so the window will feel different from one man to the next.

How long does tadalafil take to start working?

Peak blood levels arrive at a median of 2 hours after a dose, anywhere from 30 minutes to 6 hours, according to the label (Cialis prescribing information, DailyMed). Some men respond sooner. In a stopwatch-timed home study, tadalafil beat placebo from as early as 16 minutes after dosing at the higher strength tested, and 52% of men on that strength had at least one successful attempt within 30 minutes, against 35.1% of men on placebo (Rosen et al., J Sex Med 2004).

A clinical review adds a caution: it advises against telling men to expect an effect in as little as 15 minutes, because a response may take up to 2 hours for most men, and expecting a fast result can create performance anxiety or loss of confidence in the treatment (Coward and Carson review, PMC). When and how to take it is set by the label and the prescriber, not by this page.

Why does tadalafil last longer than sildenafil?

It lasts longer because the body clears it more slowly. Tadalafil’s mean terminal half-life, the time for its blood level to fall by half, is 17.5 hours in healthy volunteers (Cialis prescribing information, DailyMed). Sildenafil and its active breakdown product both have half-lives of about 4 hours (Viagra prescribing information, DailyMed).

A review of the class calls half-life the most strikingly different feature among these drugs, and links tadalafil’s longer half-life to its 36-hour window (Coward and Carson review, PMC). Both drugs block the same enzyme, PDE5, as our explainer on how ED medications work sets out. Our tadalafil vs sildenafil comparison puts onset, duration, food effects and cost side by side.

Does tadalafil work without arousal?

No. The label explains that sexual stimulation is needed to start the nitric oxide signal that the drug builds on, so “the inhibition of PDE5 by tadalafil has no effect in the absence of sexual stimulation” (Cialis prescribing information, DailyMed). MedlinePlus adds that tadalafil does not cure ED or increase sexual desire (MedlinePlus: Tadalafil). A long window means more room for things to happen naturally, not a constant effect.

How long does tadalafil stay in your system?

Tadalafil stays in the blood for days, falling by about half every 17.5 hours on average. In a pooled analysis of 237 healthy subjects, the half-life ranged from 11.5 to 29.6 hours between the 5th and 95th percentiles, so it varies a good deal from person to person (Forgue et al., Br J Clin Pharmacol 2006). Simple arithmetic on the 17.5-hour average shows the shape: roughly half remains after 17.5 hours, a quarter after 35 hours, and about one sixteenth after 70 hours.

Sources: Cialis prescribing information, DailyMed; Coward and Carson review, PMC. These are the reasons the label adjusts its instructions for kidney and liver problems and for certain medicines, and why those decisions belong to the prescriber.

The long stay matters most for safety. The label says that if a man who has taken tadalafil needs a nitrate for a life-threatening emergency, at least 48 hours should pass after his last dose before a nitrate is considered, and then only under close medical supervision (Cialis prescribing information, DailyMed). That is why emergency staff need to know when you last took it.

Does food change how tadalafil works?

No. The label states that “the rate and extent of absorption of tadalafil are not influenced by food,” so it may be taken with or without food (Cialis prescribing information, DailyMed). A pharmacology analysis found food had negligible effects on how much of the drug reached the blood, and the time of day it was taken did not change exposure much either (Forgue et al., Br J Clin Pharmacol 2006).

That is a real difference from sildenafil, where a high-fat meal delays peak levels by about 60 minutes and lowers the peak by 29% (Viagra prescribing information, DailyMed).

Do alcohol or grapefruit change it?

They can, in different ways. In the label’s studies alcohol did not change tadalafil blood levels, but the label warns that both alcohol and tadalafil widen blood vessels, and that substantial drinking (about 5 units or more) with tadalafil can bring on dizziness, a faster heart rate and a drop in blood pressure on standing (Cialis prescribing information, DailyMed). Grapefruit juice is named on the label among CYP3A4 blockers that “would likely increase tadalafil exposure,” and MedlinePlus advises talking to your doctor about grapefruit (MedlinePlus: Tadalafil).

Other medicines can raise tadalafil levels much more, as the table above shows. Tell the prescriber about every medicine and supplement you take.

How does daily tadalafil change the timing?

Tadalafil is also approved as a lower dose taken every day, without timing it to sex. With once-daily use, steady blood levels are reached within 5 days and exposure is about 1.6 times higher than after a single dose (Cialis prescribing information, DailyMed). The 1.6-fold build-up fits what the 17.5-hour half-life predicts (Forgue et al., Br J Clin Pharmacol 2006).

So on a daily plan, “how long does one pill last” stops being the question. Our guide to daily vs on-demand tadalafil explains who each approach tends to suit; which one is right is a decision for you and the prescriber.

Does a longer window mean more side effects?

Not necessarily, but some side effects show up late. The label notes that in its clinical pharmacology trials, back pain and muscle aches with tadalafil generally began 12 to 24 hours after a dose and typically resolved within 48 hours (Cialis prescribing information, DailyMed). Our tadalafil side effects page has the label’s full numbers.

When to talk to a clinician

Talk to a clinician before using tadalafil if you have heart disease, take nitrates, an alpha-blocker or any blood pressure medicine, have kidney or liver problems, or take medicines such as certain antifungals or HIV medicines that slow its clearance (Cialis prescribing information, DailyMed). Raise it too if the medicine seems not to work, rather than taking more. ED can also be a sign of a health problem worth checking, which our guide on when to see a doctor about ED covers.

Sources

1. Cialis (tadalafil) prescribing information, Eli Lilly and Company, DailyMed. Sections 2, 5, 6.1, 7, 8.7, 12.1, 12.3, 14.1 and 17, and the patient information.
2. Viagra (sildenafil citrate) prescribing information, Pfizer, DailyMed. Section 12.3.
3. Forgue ST, et al. Tadalafil pharmacokinetics in healthy subjects. Br J Clin Pharmacol. 2006
4. Porst H, et al. Efficacy of tadalafil for the treatment of erectile dysfunction at 24 and 36 hours after dosing: a randomized controlled trial. Urology. 2003
5. Rosen RC, et al. Determining the earliest time within 30 minutes to erectogenic effect after tadalafil: an at-home study. J Sex Med. 2004
6. Coward RM, Carson CC. Tadalafil in the treatment of erectile dysfunction. Ther Clin Risk Manag. 2008
7. MedlinePlus: Tadalafil. U.S. National Library of Medicine