A single 5mg dose of Cialis (tadalafil) stays in your system for roughly two to three days. The drug has a mean half-life of 17.5 hours, meaning half the dose is cleared about every 17 to 18 hours. After five half-lives, the amount left is negligible, which puts full elimination at approximately 87 to 90 hours for most healthy adults.
That said, “in your system” and “still working” are two different things. You’ll likely stop noticing effects well before the drug fully clears your bloodstream, and several factors can stretch or shorten that timeline.
How the 17.5-Hour Half-Life Works
Every 17.5 hours, your body eliminates roughly half of the tadalafil still circulating. Here’s what that looks like after a single 5mg tablet:
- After ~18 hours: about 2.5mg equivalent remains
- After ~35 hours: about 1.25mg remains
- After ~53 hours: about 0.6mg remains
- After ~70 hours: about 0.3mg remains
- After ~88 hours: trace amounts, effectively cleared
The FDA’s prescribing information confirms this, noting that after a single tablet, some active ingredient remains in your body for more than two days. For most people, the drug is essentially gone by day three or four.
How Long the Effects Actually Last
The 5mg dose was specifically designed for daily use. Researchers determined that 5mg maintains a plasma concentration high enough to keep the drug’s target enzyme suppressed throughout a 24-hour window. That’s why it’s prescribed as a once-a-day pill rather than an as-needed dose.
If you take it daily, the drug builds up to a steady level in your bloodstream, and you maintain a consistent effect around the clock. If you take a single 5mg tablet and stop, you’ll get noticeable effects for roughly 24 to 36 hours. After that, the remaining concentration drops below the threshold where most people experience a meaningful benefit, even though the drug technically lingers in your system for another day or two.
This is what makes tadalafil different from shorter-acting options. Its long half-life is the reason it earned the nickname “the weekend pill” at higher doses like 10mg or 20mg, where a single tablet can provide effects lasting up to 36 hours.
Kidney Problems Slow Elimination Significantly
Your kidneys play a major role in clearing tadalafil. If they aren’t working at full capacity, the drug stays in your system considerably longer.
FDA review data shows that people with mild kidney impairment had a half-life of about 26 hours, compared to 14 hours in healthy volunteers in the same study. Those with moderate kidney impairment had a half-life of about 22 hours. In both groups, overall drug exposure roughly doubled. That means instead of clearing the drug in three to four days, someone with reduced kidney function might carry detectable levels for four to six days after a single dose.
Liver function also matters, since tadalafil is broken down by liver enzymes, but the data is less consistent. Half-life values tend to be longer and more variable in people with liver impairment, though the pattern isn’t as predictable as it is with kidney issues.
Age, Weight, and Gender Don’t Change Much
A large analysis of 237 subjects found no clinically meaningful difference in how the body processes tadalafil based on age, body mass index, gender, or smoking status. If you’re over 65 and wondering whether the drug lingers longer, the data suggests it clears at roughly the same rate as in younger adults, assuming your kidney and liver function are healthy.
This is one of the reasons the 5mg daily dose doesn’t typically require adjustment for older adults. The drug behaves predictably across a wide range of body types and demographics.
Medications That Can Delay Clearance
Tadalafil is broken down primarily by a specific set of liver enzymes. Certain medications compete for or block those same enzymes, which slows tadalafil’s breakdown and keeps it circulating longer. The most common culprits include antifungal medications like ketoconazole and itraconazole, certain antibiotics like clarithromycin, and HIV protease inhibitors like ritonavir. Grapefruit juice has a similar, though milder, effect.
If you take any of these regularly, your effective half-life for tadalafil will be longer than the standard 17.5 hours, and the drug will remain in your system for additional time. This also increases the intensity of both the desired effects and potential side effects like headache, flushing, or muscle aches.
Single Dose vs. Daily Use
If you’re taking 5mg daily as prescribed, the drug never fully leaves your system between doses. It reaches a steady state after about four to five days of consistent use, meaning the amount entering your body each day equals the amount being cleared. At steady state, you carry a relatively stable level of tadalafil at all times.
If you stop taking it after daily use, expect it to take longer to fully clear than it would after a single pill. The accumulated baseline means you’re starting from a higher level, and the same half-life math applies from that higher starting point. Most people are fully clear within four to five days after stopping daily use.