Most Celexa (citalopram) side effects are temporary and fade within the first two to four weeks of treatment as your body adjusts to the medication. Some effects, particularly sexual side effects and weight changes, can persist for months or longer. How long any given side effect lasts depends on which symptom you’re experiencing, your dose, and whether you’re starting, taking, or stopping the medication.
The First Few Weeks: Start-Up Side Effects
When you first begin taking Celexa, your brain is adjusting to higher serotonin levels. That adjustment period commonly produces nausea, headaches, trouble sleeping, drowsiness, dry mouth, and increased sweating. These early side effects typically wear off after a few weeks. For most people, the worst of it hits in the first week and gradually improves by weeks two through four.
Sexual side effects like low libido, difficulty reaching orgasm, or changes in arousal also tend to appear early. The NHS notes these usually stop after the first couple of weeks for many people, though this is one category where the timeline varies widely from person to person.
If a start-up side effect hasn’t improved after four to six weeks, it’s less likely to resolve on its own. That’s generally the point where it makes sense to talk to your prescriber about adjusting the dose or trying a different medication.
Side Effects That Can Stick Around
Not every side effect follows the “few weeks and done” pattern. Some persist for as long as you take the medication, and a few can outlast it.
Sexual dysfunction is the most commonly reported persistent side effect. While some people find it resolves early on, others experience reduced libido, difficulty with orgasm, erectile dysfunction, or genital numbness for the entire duration of treatment. Australia’s Therapeutic Goods Administration has warned that these effects can persist for weeks to years, and in some cases continue even after stopping the medication. In reported cases of long-lasting sexual dysfunction after discontinuation, symptoms persisted for 12 months to 3.5 years.
Weight changes tend to develop gradually rather than appearing right away. A large study tracking first-time antidepressant users found that citalopram produced weight gain comparable to sertraline: roughly a few pounds at six months, with continued gradual gain over two years. This isn’t dramatic for most people, but it’s a slow-building effect rather than something that peaks and resolves.
Emotional blunting, a feeling of being dulled or flattened emotionally, is another effect some people notice for as long as they remain on the medication. It’s distinct from depression itself and often improves if the dose is lowered.
What Happens When You Stop
Discontinuation symptoms are a separate category from the side effects you experience while taking Celexa. When you reduce your dose or stop the medication, withdrawal symptoms can appear within one to two days. Common ones include dizziness, irritability, “brain zaps” (brief electrical-sensation feelings in the head), nausea, flu-like symptoms, and vivid dreams.
For some people, these symptoms are mild and pass within a few days. For others, they can be more severe and last months or, according to guidelines from the UK’s National Institute for Health and Care Excellence, sometimes more than a year. The Royal College of Psychiatrists notes that withdrawal symptoms usually improve quickly, sometimes within hours, if you restart the medication, which is one way to confirm that what you’re feeling is withdrawal rather than a return of the underlying condition.
Tapering slowly rather than stopping abruptly significantly reduces the risk of severe withdrawal. The slower you taper, the less your brain has to scramble to readjust.
Older Adults and Dose Differences
If you’re over 60, Celexa generally works the same way and produces similar side effects. The key difference is a lower maximum recommended dose (20 mg instead of 40 mg) because higher doses carry a greater risk of affecting heart rhythm in older adults. This dose-dependent heart rhythm effect is why the FDA capped the maximum dose at 40 mg for all adults.
Older adults are also more prone to developing low sodium levels (hyponatremia) while on citalopram, especially if they take blood pressure medications that act as diuretics. Symptoms of low sodium, like confusion, headache, or weakness, can mimic other side effects and may not resolve without a dose adjustment or medication change.
Rare but Serious Reactions
Serotonin syndrome is rare with Celexa alone but becomes a real risk when combining it with other medications that raise serotonin, including certain migraine drugs, other antidepressants, or some supplements. Symptoms appear within hours of a dose change or new drug interaction and include rapid heart rate, high blood pressure, agitation, confusion, muscle twitching, heavy sweating, and shivering. Severe cases can cause high fever, seizures, or an irregular heartbeat. This is a medical emergency, not a side effect that resolves on its own.
A Practical Timeline
- Days 1 to 7: Start-up side effects like nausea, headache, and sleep disruption are usually at their worst.
- Weeks 2 to 4: Most common side effects fade noticeably. This is also when therapeutic benefits typically begin.
- Weeks 4 to 6: Any side effect still present at this point is less likely to resolve without a dose or medication change.
- Months 2 and beyond: Persistent effects like sexual dysfunction, emotional blunting, or gradual weight gain may continue for the duration of treatment.
- After stopping: Withdrawal symptoms can begin within one to two days and last anywhere from a few days to several months, depending on how quickly you taper.
The overall pattern is that your body does most of its adapting in the first month. Side effects that clear that hurdle tend to be the ones you’ll manage for as long as you take the medication, making them worth discussing with your prescriber rather than waiting out.