How Long Cialis Lasts: Up to 36 Hours, When It Kicks In, Food

Below: when Cialis kicks in, when it peaks, what food changes, the daily option, and how it compares with Viagra. Every timing figure comes from the FDA label or a published trial. Generic tadalafil carries the same label as the brand. We do not give doses; the prescriber sets the strength.

How long does Cialis take to work?

The label gives the peak, not a start time. It says peak blood levels come "between 30 minutes and 6 hours (median time of 2 hours)" after a single pill (DailyMed: Cialis label). Median means the middle value: half of men peaked sooner, half later.

A trial timed it with a stopwatch. At the higher tablet strength, it found "a significant erectogenic response" from "30 minutes down to 16 minutes after dosing" (Rosen et al., J Sex Med 2004, PubMed). Erectogenic means helping an erection. So some men notice it within half an hour, while for others it takes a couple of hours to build. MedlinePlus, the US National Library of Medicine's drug guide, says as-needed tadalafil is taken "usually at least 30 minutes before sexual activity and not more often than once every 24 hours" (MedlinePlus: tadalafil, read 14 November 2026).

The pill does not cause an erection on its own. The label says "the inhibition of PDE5 by tadalafil has no effect in the absence of sexual stimulation". You still need arousal for it to work.

How long does tadalafil last in your body?

Half-life is the time it takes for half of the drug to leave your blood. The label says "the mean terminal half-life is 17.5 hours in healthy subjects" (DailyMed: Cialis label). Sildenafil, the drug in Viagra, has a half-life of about 4 hours.

In plain terms: about 17 to 18 hours after the peak, half of the tadalafil is still in your blood. That slow fade is what gives Cialis its long window. It is also why a side effect can turn up the next day.

Does Cialis really work for 36 hours?

The 36-hour figure comes from trials, not marketing. One trial asked men to try sex 24 or 36 hours after one pill. "Thirty-six hours after tadalafil dosing, 59.2% of intercourse attempts were successful versus 28.3% in the placebo group" (Porst et al., Urology 2003, PubMed). Placebo means a dummy pill. At about 24 hours, the rates were 52.9% versus 29.1%.

So the window is real, but it is not a switch. The effect is strongest in the first hours and slowly fades. Arousal is still needed at every point.

Cialis with food

Food does not slow Cialis down. The label says: "The rate and extent of absorption of tadalafil are not influenced by food; thus CIALIS may be taken with or without food" (DailyMed: Cialis label). This is a real difference from Viagra, where a fatty meal delayed the peak by about an hour.

Grapefruit is a different matter. The label says "other CYP3A4 inhibitors, such as erythromycin, itraconazole, and grapefruit juice, would likely increase tadalafil exposure". In plain words, grapefruit juice may keep more tadalafil in your blood. Ask the prescriber if you drink it often.

Daily Cialis: a different way to use the same drug

Tadalafil also comes as a low-strength daily pill. Taken every day, it keeps a steady level in the blood, so timing stops mattering. The label says the daily form "provides continuous plasma tadalafil levels" (DailyMed: Cialis label). That steady level is also why the prescriber checks your other medicines and how much you drink.

Daily tadalafil is also approved for an enlarged prostate. Whether daily or as-needed costs less depends on how often you use it. Our daily tadalafil cost guide works out the break-even.

Why age, alcohol and other medicines matter

The body clears tadalafil more slowly in older men. The label says men aged 65 or over had "25% higher exposure (AUC) with no effect on C max". Exposure means the total amount of drug the body sees over time.

The long half-life also stretches the safety rules. The label says that in an emergency, "at least 48 hours should elapse after the last dose of CIALIS before nitrate administration is considered". Nitrates are chest-pain drugs, and you must not combine them with any ED pill. Heavy drinking with Cialis can cause dizziness and a drop in blood pressure. Our ED pill side effects guide covers both.

Back pain is the side effect that shows the long timing best. The label says it "generally occurred 12 to 24 hours after dosing and typically resolved within 48 hours".

Cialis vs Viagra: how long each one lasts

Viagra (sildenafil) has a half-life of about 4 hours and a window of a few hours. Cialis lasts up to 36 hours. Neither is better for everyone: some men prefer the shorter drug, some want the longer window. Our guide to how long Viagra lasts has the sildenafil timing, and sildenafil vs tadalafil compares the two on price and side effects.

If an erection lasts more than 4 hours, get emergency care. The label warns that priapism, a painful erection lasting over 6 hours, "can result in irreversible damage to the erectile tissue" if not treated promptly.

What generic tadalafil costs

Generic tadalafil is the same drug as Cialis and carries the same label. These programs publish a price that includes the visit. The table is ranked on our score, with prices from each seller's own page as checked November 14, 2026.

The lowest per-dose price for any tadalafil plan right now is $1.80 at Rex MD, daily plans included. Every plan and read date is on our tadalafil price page and generic tadalafil price page.