How long does Cialis last?

One dose of Cialis (tadalafil) can work for up to 36 hours. Its FDA label says as-needed Cialis improved erectile function compared with placebo for up to 36 hours after a dose, and that some men can have sex 30 minutes after taking it. Tadalafil peaks at a median of 2 hours and has a half-life of 17.5 hours, which is why it outlasts Viagra (sildenafil) by so much. Taken daily at a low dose, it keeps a steady level, so there is no window to plan around at all.

“Lasting” here means the time in which the pill can help you get an erection when you are aroused. It doesn’t cause an erection on its own, and an erection that won’t go down after 4 hours needs emergency care. For how the other ED pills compare, see how long Viagra lasts.

Cialis timing at a glance

All figures are from the Cialis label.

How fast Cialis starts working

The label tells men to take as-needed Cialis at least 30 minutes before sex. One trial measured exactly that: 223 men used a stopwatch to time how soon after a dose they had an erection that led to successful sex. Within 30 minutes, 52% of men on 20 mg and 38% on 10 mg did, against 35% on placebo.

Most men will notice it later than that. Tadalafil reaches its highest level in the blood anywhere from 30 minutes to 6 hours after a dose, with a median of 2 hours. Unlike sildenafil, it isn’t slowed by food: the label says the rate and extent of absorption aren’t affected by a meal, so you can take it with dinner.

How long the window stays open

Two trials in the label tested Cialis a full day and a day and a half after the dose:

Scroll sideways to see the full table

So the effect at 36 hours was close to the effect at 24 hours. That is the basis for the label’s statement that most patients’ ability to have sex is improved for up to 36 hours, and for the “weekend pill” reputation. The label asks clinicians to take that long window into account when advising you when to take it.

How long it stays in your body

Tadalafil’s mean half-life in healthy men is 17.5 hours, against about 4 hours for sildenafil. Working from that average, about half the peak level is left roughly 17.5 hours after a dose and about a quarter after 35 hours. Everyone clears it at a different speed, so treat those as rough guides.

That long tail shows up in two places on the label:

• Nitrates. Cialis must never be taken with nitrates such as nitroglycerin. If a man who has taken Cialis needs a nitrate in a life-threatening emergency, at least 48 hours should pass after his last dose first, and only under close medical monitoring. Tell any emergency team that you take it.
• Back and muscle pain. When tadalafil causes back pain or muscle aches, they generally start 12 to 24 hours after the dose and usually ease within 48 hours.

Daily Cialis: no window at all

Daily Cialis is a different way of using the same drug. You take 2.5 mg at about the same time each day, increased to 5 mg if needed, without timing it to sex. The level in your blood builds to a steady state within 5 days, at about 1.6 times the level after a single dose.

In three trials with 853 men, daily Cialis improved erectile function, and in the 6-month study its effect didn’t fade over time. Side effects were less common than with the higher as-needed doses: in the 12-week trials, headache affected 3% of men on 2.5 mg and 6% on 5 mg, against 5% on placebo.

The 5 mg daily dose is also approved for the urinary symptoms of an enlarged prostate (BPH), alone or with ED. Daily dosing can make sense if you have sex often, want to stop planning, or have both conditions. See daily tadalafil providers.

What changes how long it lasts

Age. Men 65 and over clear tadalafil more slowly, giving 25% higher exposure with no change in the peak. The label doesn’t adjust the dose for age alone.

Kidneys. In men with moderately reduced kidney function (creatinine clearance 30 to 80 mL/min), exposure roughly doubled. The label limits as-needed Cialis to a 5 mg start and 10 mg at most once every 48 hours at 30 to 50 mL/min, and to 5 mg once every 72 hours below 30 mL/min or on dialysis, where daily Cialis isn’t recommended.

Liver. The dose may need adjusting with mild or moderate liver disease, and Cialis isn’t recommended with severe liver disease.

Other medicines. Strong inhibitors of the liver enzyme CYP3A4, such as ketoconazole and ritonavir, raise tadalafil levels. With them, as-needed Cialis is capped at 10 mg no more than once every 72 hours, and daily Cialis at 2.5 mg. Inducers such as rifampin do the opposite and lower the level.

Alcohol. Alcohol doesn’t change tadalafil levels, but both lower blood pressure. The label warns that 5 or more units of alcohol with Cialis can cause dizziness, a faster heart rate, headache and a drop in blood pressure when you stand.

Taking more doesn’t make it last longer

As-needed Cialis is limited to one dose a day. A second tablet doesn’t extend the window; it raises your level and your risk of side effects. In the label’s as-needed trials, headache affected 11% of men on 10 mg and 15% on 20 mg, against 5% on placebo, and indigestion 8% and 10%, against 1%. If the timing doesn’t suit you, the options are a dose change, daily Cialis or a different drug, agreed with your clinician. Our sildenafil vs tadalafil guide compares the side effects in full.

What generic Cialis costs online

Generic tadalafil is the FDA-approved generic of Cialis and needs a prescription; licensed telehealth providers can prescribe it after an online review. Prices on each provider’s own site, as of October 2026:

Prices usually rise with strength, so check the price for the dose you’re prescribed. For the terms behind each price, see where generic Cialis is cheapest and what Cialis costs, or compare providers in our ED rankings and on the ED hub.

The bottom line

Cialis can work within 30 minutes for some men, usually peaks around 2 hours, and keeps working for up to 36 hours after one dose, with similar results at 24 and 36 hours in its trials. Its 17.5-hour half-life is behind that, and it is also why nitrates need a 48-hour gap. Daily Cialis removes the timing question altogether. Age, kidney or liver disease and some medicines make it last longer, so tell your clinician about them before you start.