Citalopram has an average half-life of about 35 hours, meaning it takes roughly 35 hours for your body to eliminate half of a dose. Using the standard pharmacokinetic rule that a drug is essentially cleared after five half-lives, citalopram leaves most people’s systems within about 7 to 8 days after the last dose.
That’s the short answer, but the full picture is more nuanced. Your age, liver health, genetics, and how long you’ve been taking the medication all affect how quickly your body processes it. And even after the drug itself is gone, your body may still be adjusting to its absence.
The Half-Life Explained
A drug’s half-life is the time it takes for the concentration in your blood to drop by half. According to the FDA label for citalopram, the mean terminal half-life is about 35 hours. After one half-life (35 hours), half the drug remains. After two half-lives (about 70 hours), a quarter remains. By five half-lives, roughly 97% of the drug has been eliminated.
For most healthy adults, that math works out to approximately 7 to 8 days for near-complete clearance. However, the half-life isn’t a fixed number for everyone. Studies show it can range from about 23 to 45 hours depending on the individual, which means total clearance could happen as early as 5 days or stretch past 9 days.
Steady State and Why Duration of Use Matters
If you’ve been taking citalopram daily, the drug accumulates in your body until it reaches what’s called steady state, where the amount you absorb each day roughly equals the amount you eliminate. FDA data shows this happens within about one week of daily dosing. At steady state, plasma concentrations are about 2.5 times higher than what you’d see after a single dose.
This means someone who has been on citalopram for months will start their elimination clock with more of the drug in their system than someone who took it only once. The half-life itself doesn’t change, but the total amount that needs to be cleared is greater, so you’re effectively adding an extra half-life or two to the total clearance window in practical terms.
Active Metabolites Stick Around Longer
Your liver breaks citalopram down into several byproducts. The most significant is a compound called demethylcitalopram, which reaches about half the concentration of the parent drug at steady state. This metabolite has its own half-life, estimated between 66 and 92 hours, meaning it lingers in your body considerably longer than citalopram itself.
While these metabolites are far less active than the original drug, they are still detectable in blood and urine. If you’re concerned about detection for any reason, the metabolites can extend the window during which traces of citalopram-related compounds are present to roughly two weeks or more after your final dose.
Factors That Slow Elimination
Age
Older adults process citalopram more slowly. Data from Health Canada’s product monograph shows that in elderly patients, the half-life can extend to anywhere from 1.5 to 3.75 days (36 to 90 hours), and clearance is noticeably reduced. This means full elimination in an older adult could take 10 days to two weeks or longer.
Liver Health
Because citalopram is primarily processed in the liver, reduced liver function has a dramatic effect. In patients with impaired liver function, the half-life roughly doubles to about 83 hours compared to 37 hours in healthy adults. That pushes total clearance time to approximately 17 days.
Genetics
Your body relies on a specific liver enzyme (part of the CYP2C19 family) to break down citalopram. Some people carry genetic variations that make this enzyme work much more slowly. Research shows that “poor metabolizers” of this enzyme have a significantly longer half-life and lower clearance rates than people with normal enzyme activity. If you’ve ever had pharmacogenomic testing done, this result would be on your report. Without testing, there’s no easy way to know your status, though roughly 2 to 3% of people of European descent and up to 15 to 20% of people of East Asian descent are poor metabolizers.
Detection in Drug Tests
Citalopram is not a controlled substance and isn’t included in standard workplace drug panels. However, there have been documented cases of SSRIs like citalopram causing false positives for certain substances on immunoassay screening tests. If this happens, a confirmatory test will distinguish citalopram from the flagged substance.
For specialized clinical testing, citalopram and its primary metabolite can be detected in urine and blood. Given the parent drug’s half-life of 23 to 45 hours and the metabolite’s half-life of 66 to 92 hours, traces could show up in urine for roughly 10 to 14 days after the last dose, though the exact window depends on the sensitivity of the test and your personal metabolism.
Withdrawal Symptoms Can Outlast the Drug
One of the most important things to understand is that even after citalopram has fully cleared your bloodstream, you may still feel its absence. Your brain adapted to the drug’s presence, and it needs time to readjust.
Withdrawal symptoms typically begin within one to two days of stopping or reducing your dose, sometimes after missing even a single dose. Common experiences include dizziness, irritability, nausea, “brain zaps” (brief electric shock sensations), sleep disruption, and mood changes. For many people, these symptoms are mild and resolve within a few weeks. But according to guidelines from the U.K.’s National Institute for Health and Care Excellence (NICE), some people experience more severe withdrawal that lasts months or, in rarer cases, over a year.
This is why gradual tapering, rather than stopping abruptly, is the standard approach. Tapering gives your brain time to recalibrate while the dose slowly decreases, reducing both the intensity and duration of withdrawal symptoms. The speed of a taper should be guided by how you’re responding to each reduction, not a fixed calendar.
Quick Reference: Estimated Clearance Times
- Healthy adults (single dose): 5 to 9 days
- Healthy adults (steady state after daily use): 7 to 10 days
- Older adults: 10 to 14 days or longer
- Reduced liver function: up to 17 days
- Active metabolites fully cleared: up to 2 weeks beyond the parent drug
These estimates reflect the time for blood levels to drop below clinically meaningful thresholds. Trace amounts detectable by sensitive lab equipment may persist slightly longer.