Quick answer: The most common Celexa side effects in FDA trials were nausea (21% vs 14% on placebo), dry mouth (20% vs 14%), sleepiness (18% vs 10%), trouble sleeping and extra sweating. Most show up in the first one to two weeks and ease as your body adjusts. A few, like sexual changes and sweating, can linger. Rare problems such as an irregular heartbeat, serotonin syndrome or low sodium need prompt medical care.
Picture day three on a new prescription. Your stomach feels off after breakfast, your mouth is dry by noon, and you are yawning at your desk by 3 p.m. That is a very typical start, and it is the reason this guide to Celexa side effects is built like a calendar instead of a long alphabetical list. What you feel on Celexa (citalopram) tends to change with time: some effects arrive fast and leave fast, some appear later, and a small number stick around.
Celexa is an SSRI antidepressant approved in the US for major depression. It raises serotonin activity in the brain, and serotonin also works in the gut, blood platelets, sweat glands and more. That wide reach explains most of the side effects below. If you want the dosing basics first, our guide to Celexa doses and the 40 mg ceiling covers them.
One timing fact helps make sense of everything else. Citalopram has an average half-life of about 35 hours, and blood levels reach a steady state after roughly one week of daily dosing, according to the Celexa prescribing information. So the first week is a period of rising levels, and your body is adapting the whole time.
Days 1-7: The start-up week
The first week is when stomach and “wired or tired” effects are most likely. A 2026 analysis of the World Health Organization’s VigiBase reporting database looked at when SSRI side effects were first reported. Nausea had a median onset of just one day. Insomnia, dizziness and headache followed at about two days, agitation at three and fatigue at four. That study pooled six SSRIs, including citalopram, so it shows a class pattern rather than Celexa-only numbers.
What tends to show up
- Nausea or an unsettled stomach. This is the single most common complaint. Some people also get loose stools or mild indigestion.
- Dry mouth. Often noticed within the first few days.
- Sleepiness or, in some people, the opposite. Celexa makes many people drowsy, but a smaller group feels restless or has trouble falling asleep.
- Jitteriness, yawning or a slight tremor. These usually feel more odd than harmful.
What you should not expect yet
Mood benefits usually lag behind side effects. The NIH’s StatPearls review of citalopram puts the start of antidepressant effect at about one to four weeks, with a full response often taking eight to 12 weeks. Feeling the downsides before the upsides is normal, and frustrating. Our post on how long Celexa takes to start working breaks that timeline down.
One more first-week point: if you feel sleepy or dizzy, hold off on driving or using machinery until you know how the medicine affects you. The NHS gives the same advice for citalopram.
Weeks 2-4: What fades and what starts
For many people, weeks two through four are the turning point. The NHS notes on its citalopram side effects page that most side effects ease after a couple of weeks as the body gets used to the medicine, though some can last longer. Nausea, in particular, is often described in guidelines as short-lived.
What often fades
- Morning nausea and stomach upset
- Early headaches and light-headedness
- The “buzzy” restless feeling some people get in week one
What may appear now
Sexual side effects tend to surface a little later than stomach effects. In the VigiBase analysis, sexual dysfunction had a median reporting time of about 16.5 days. That lines up with what many people notice: once the dose is stable, orgasm may take longer, desire may dip, or ejaculation may be delayed.
This window also matters for dose changes. Prescribers often start at 20 mg and may raise the dose after at least a week. Any increase can briefly bring back early-week effects like nausea or sleepiness, so a short “second wave” after a dose bump is not unusual.
Mood check: the most important thing to watch
The FDA asks families and caregivers to watch closely for changes in mood or behavior during the first few months and after any dose change. New or worse anxiety, agitation, panic, irritability, trouble sleeping, acting on dangerous impulses, or thoughts of self-harm are reasons to call the prescriber the same day. If you or someone you love is thinking about suicide, call or text 988 (the Suicide & Crisis Lifeline, open 24/7 in the US), or call 911 if there is immediate danger.
Months 2-6: Settling in
By the second month, the picture usually becomes clearer. The early stomach effects have mostly gone. Mood benefits, if they are coming, are usually visible. What is left tends to be the side effects that last.
A helpful real-world data point comes from the UK GENPOD trial, which followed 601 adults with depression taking citalopram or another antidepressant. A 2014 analysis in Psychopharmacology (Crawford and colleagues) tracked side effects at 2, 6 and 12 weeks. Tremor, dry mouth, constipation, dizziness, impotence and difficulty ejaculating all declined over 12 weeks. Agitation, sleep difficulty and drowsiness rose, peaked around week six, and then declined. The total number of side effects fell over time.
The researchers also made a fair point: some symptoms that do not fade may be depression itself rather than the drug. Poor sleep, low energy and appetite changes are classic depression symptoms, so it is worth tracking how you felt before starting.
What may linger in this window
- Sweating, especially at night. In the VigiBase study, excessive sweating had a late median onset of about 76 days.
- Sexual changes, which can ease for some people and persist for others.
- Weight or appetite shifts. Weight gain had a median onset of about 31 days in the same database.
- Daytime tiredness or yawning, which can be dose-related.
Long-term (6+ months): What lingers and what to keep an eye on
Many people stay on citalopram for six months to a year or longer to lower the chance of depression coming back. Long-term use is generally well tolerated, but a few issues deserve ongoing attention.
- Persistent sexual side effects. These are one of the most common reasons people ask about switching. They are worth raising, because options exist.
- Gradual weight change. Short trials showed a tiny average weight loss, but some people report gradual gain over months.
- Bleeding risk with other medicines. This does not fade with time. It matters every time you add a painkiller, aspirin or blood thinner.
- Sodium levels in older adults. Low sodium can develop at any point, and older adults on diuretics are at greater risk.
- New medicines and the heart. Starting another drug that affects heart rhythm, or one that blocks the enzyme CYP2C19, can change your risk years into treatment.
Long-term users also face one predictable event: stopping. Discontinuation symptoms are a separate topic, covered further down and in its own post.
How common are Celexa side effects? The FDA trial numbers
The table below comes from the adverse-reaction table in the FDA-approved Celexa label (also posted on DailyMed). It pools placebo-controlled depression trials with 1,063 people on Celexa and 446 on placebo, at doses from 10 to 80 mg a day for up to six weeks. It lists effects reported by at least 2% of Celexa users and more often than with placebo.
The “extra” column is the simplest way to read it. It shows roughly how many more people out of 100 had the effect on Celexa than on a sugar pill.
| Side effect | Celexa | Placebo | Extra per 100 people |
|---|---|---|---|
| Nausea | 21% | 14% | 7 |
| Dry mouth | 20% | 14% | 6 |
| Somnolence (sleepiness) | 18% | 10% | 8 |
| Insomnia | 15% | 14% | 1 |
| Increased sweating | 11% | 9% | 2 |
| Diarrhea | 8% | 5% | 3 |
| Tremor | 8% | 6% | 2 |
| Ejaculation disorder (men; mainly delay) | 6% | 1% | 5 |
| Dyspepsia (indigestion) | 5% | 4% | 1 |
| Fatigue | 5% | 3% | 2 |
| Rhinitis (runny nose) | 5% | 3% | 2 |
| Vomiting | 4% | 3% | 1 |
| Anxiety | 4% | 3% | 1 |
| Anorexia (low appetite) | 4% | 2% | 2 |
| Agitation | 3% | 1% | 2 |
| Impotence (men) | 3% | under 1% | about 2-3 |
| Abdominal pain | 3% | 2% | 1 |
| Sinusitis | 3% | under 1% | about 2-3 |
| Painful periods (women) | 3% | 2% | 1 |
| Decreased libido | 2% | under 1% | about 1-2 |
| Yawning | 2% | under 1% | about 1-2 |
| Joint pain / muscle pain | 2% each | 1% each | 1 |
Three things the table tells you
- Placebo causes “side effects” too. Insomnia hit 15% on Celexa but 14% on placebo, so most of that sleeplessness was not the drug. Headache, dizziness and constipation were left off the table entirely because they were just as common, or more common, with placebo.
- Sleepiness beats insomnia. Somnolence had the largest gap over placebo of any effect. For most people, Celexa leans sedating.
- Most people stayed on it. About 16% of people on Celexa stopped a trial early because of side effects, compared with 8% on placebo. Nausea (4%), insomnia (3%), sleepiness (2%) and dizziness (2%) were the top reasons.
A caveat: trials lasted six weeks or less and relied on what people reported. Sexual side effects are known to be under-reported unless doctors ask directly, so real-world rates are likely higher than the table suggests.
Rare but serious Celexa side effects
These are uncommon, but they are the reason to know your warning signs. Each one below includes what it may feel like and what to do.
Suicidal thoughts in people under 25 (boxed warning)
Celexa carries the FDA’s strongest warning, shared by all antidepressants. In pooled trials, antidepressants raised the rate of suicidal thoughts and behaviors in people age 24 and younger: about 14 extra cases per 1,000 patients under 18, and about 5 extra per 1,000 in ages 18-24. In adults 25 and older, rates did not rise.
What it feels like: darker thoughts than usual, hopelessness, new restlessness or agitation, impulsive behavior, or thinking about death. What to do: call the prescriber right away. In a crisis, call or text 988, or call 911. Do not stop the medicine suddenly on your own.
QT prolongation (heart rhythm changes)
Citalopram can lengthen the QT interval on an ECG in a dose-dependent way. In a dedicated heart study, the average increase over placebo was about 8.5 milliseconds at 20 mg and 18.5 at 60 mg. That is why the FDA’s 2012 safety communication says doses above 40 mg a day are not recommended, and 20 mg is the limit for some groups (see below). Our deep-dive on Celexa and QT prolongation explains who needs an ECG.
What it feels like: often nothing. When symptoms happen, they include a racing or fluttering heartbeat, dizziness, shortness of breath or fainting. What to do: fainting, chest pain or a pounding irregular heartbeat means 911. Milder palpitations still deserve a same-day call.
Serotonin syndrome
This happens when serotonin activity climbs too high, most often when Celexa is combined with other serotonin-raising drugs. Examples include triptans for migraine, tramadol, other antidepressants, lithium, St. John’s wort and MAO inhibitors.
What it feels like: agitation or confusion, fast heartbeat, heavy sweating, fever, shivering, twitchy or stiff muscles, overactive reflexes, poor coordination, nausea or diarrhea. What to do: severe symptoms such as high fever, rigid muscles or confusion are an emergency, so call 911. Read more in our guide to serotonin syndrome on Celexa.
Hyponatremia (low sodium), especially in older adults
SSRIs can trigger SIADH, a hormone imbalance that makes the body hold water and dilutes blood sodium. The label names older adults, people taking diuretics (“water pills”) and people who are dehydrated as higher risk. StatPearls adds female sex and low body weight as risk factors.
What it feels like: headache, trouble concentrating, memory problems, confusion, weakness or unsteadiness that can lead to falls. Severe cases can cause hallucinations, fainting or seizures. What to do: call the prescriber promptly. Severe confusion or a seizure needs 911. Older adults may get a sodium blood test when starting or changing the dose.
Bleeding risk with NSAIDs and blood thinners
Platelets need serotonin to help blood clot. SSRIs reduce that supply, so bleeding risk goes up, and more so with aspirin, ibuprofen, naproxen, other antiplatelet drugs or warfarin.
What it feels like: easy bruising, nosebleeds, bleeding gums, or more worrying signs like black or bloody stools or vomit that looks like coffee grounds. What to do: ask your pharmacist before taking over-the-counter pain relievers. Black stools or vomiting blood need emergency care.
Angle-closure glaucoma
Many antidepressants, including citalopram, can widen the pupil slightly. In people with naturally narrow eye drainage angles who have not had preventive laser treatment, this can trigger a sudden glaucoma attack.
What it feels like: eye pain, blurred vision, colored halos or rings around lights, a red or swollen eye, sometimes with nausea. What to do: this is an emergency. MedlinePlus advises getting help right away. If you know you have narrow angles, tell your prescriber before starting.
Mania or hypomania
In trials, mania or hypomania appeared in about 0.1% of people without a known bipolar diagnosis. The risk is higher in people with undiagnosed bipolar disorder, which is why prescribers ask about personal and family history first.
What it feels like: needing little sleep but feeling full of energy, racing thoughts, talking fast, unusual risk-taking or spending, or extreme irritability. What to do: call your prescriber promptly. Family members often notice this first.
Seizures
Seizures are rare. In trials they occurred in 0.3% of people on Celexa versus 0.5% on placebo. Still, the label advises caution for anyone with a seizure history.
What it feels like: a seizure may involve jerking, staring spells or loss of awareness. What to do: a first seizure, or one lasting more than five minutes, means 911.
Who’s at higher risk of Celexa side effects?
Some people end up with more citalopram in their blood from the same pill. More drug means more chance of dose-related effects, including QT changes. The FDA caps the dose at 20 mg a day for the groups below.
| Group | Why risk is higher | What the label advises |
|---|---|---|
| Adults over 60 | Drug lingers longer. Exposure rose about 23-30% and half-life 30-50% versus younger adults. Higher risk of low sodium and falls. | Max 20 mg/day |
| Liver impairment | Clearance fell 37% and half-life doubled in studies | Max 20 mg/day |
| CYP2C19 poor metabolizers | A genetic variant slows breakdown. Total exposure (AUC) rose about 107%. | Max 20 mg/day |
| Taking a CYP2C19 blocker (e.g., cimetidine) | Same effect as being a poor metabolizer | Max 20 mg/day |
| Heart rhythm risks (long QT, slow heart rate, low potassium or magnesium, recent heart attack, heart failure) | Bigger effect of any QT lengthening | Generally not recommended; ECG and electrolyte checks if used |
A closer look at CYP2C19
CYP2C19 is a liver enzyme that helps clear citalopram. The CPIC pharmacogenetics guideline for SSRIs estimates that roughly 2-15% of people are poor metabolizers, depending on ancestry. Most people never learn their status. If you have had a genetic test (sometimes done for clopidogrel or other drugs), share the result with your prescriber. CPIC suggests poor metabolizers consider a lower starting dose or a different antidepressant.
Several common medicines can also slow CYP2C19, including omeprazole, esomeprazole and fluconazole, according to StatPearls. That is one more reason to keep a current medication list with your pharmacist, and to mention Celexa every time a new prescription is written.
Side effects with their own deep-dive guides
Four topics come up so often that each has a full post. Here is the short version of each.
Sexual side effects
In the label’s pooled trials, about 6.1% of men reported delayed or abnormal ejaculation, 3.8% lower desire and 2.8% erection problems, all far above placebo. Women can have lower desire or trouble reaching orgasm. Timing, dose and add-on strategies are covered in our guide to Celexa sexual side effects.
Weight changes
Short-term trials showed an average loss of about 0.5 kg (around 1 pound) on Celexa, versus no change on placebo. Longer-term experience is more mixed, and some people gain weight as appetite returns. We look at the evidence in does Celexa cause weight gain?
Sleep problems
Celexa is more likely to make you drowsy than keep you awake, but restless nights do happen, especially early on. Changing the time of day you take it is a common fix to ask about. Our post on Celexa and insomnia covers it. If a sleep aid is being considered, it helps to understand how Ambien’s side effects differ first.
Withdrawal (discontinuation syndrome)
Stopping abruptly can cause dizziness, nausea, irritability, “brain zaps,” vivid dreams and flu-like feelings. A gradual taper planned with your prescriber lowers the risk. Details are in our Celexa withdrawal guide.
Coping with common Celexa side effects
Small habits can make the adjustment weeks easier. None of these replace advice from your own care team, and you should never change your dose without talking to them.
| Side effect | Practical tip | When to call your prescriber |
|---|---|---|
| Nausea | Take your dose with food (the label allows with or without). Eat small, bland meals and sip fluids. | Vomiting that keeps you from holding down fluids, or nausea past 2-3 weeks |
| Dry mouth | Sip water often, chew sugar-free gum, and limit caffeine and alcohol. Keep up dental checkups. | Mouth sores, trouble swallowing, or it is affecting your teeth |
| Daytime sleepiness | Ask whether taking it at bedtime makes sense. Avoid driving until you know how you react. | Sleepiness that affects work or safety after the first few weeks |
| Insomnia | Ask whether a morning dose would help. Keep a regular sleep schedule and cut late caffeine. | Sleep loss lasting more than a week or two, or paired with agitation |
| Sweating | Wear breathable layers, keep the bedroom cool, and use an antiperspirant at night. | Drenching sweats with fever, confusion or a racing heart (possible serotonin syndrome) |
| Diarrhea | Drink plenty of fluids, and choose simple foods for a day or two. | Black or bloody stools, or signs of dehydration |
| Headache | Ask your pharmacist which pain reliever fits. Acetaminophen avoids the NSAID bleeding concern. | Headache with confusion or unsteadiness, especially if you are over 60 (possible low sodium) |
| Tremor or jitteriness | Cut back on caffeine. It often settles within a few weeks. | Muscle stiffness, twitching or fever |
| Sexual changes | Track when it started and talk openly about it. Dose timing or other options may help. | Any time it bothers you enough that you are thinking of stopping |
| Mood worsening | Tell a trusted person what to watch for. Keep follow-up visits. | Right away. Call or text 988 in a crisis, or 911 for immediate danger. |
Alcohol is worth a separate word. It can worsen drowsiness and mood, and the NHS advises avoiding it while on citalopram. If you drink, talk it through with your prescriber.
Frequently asked questions about Celexa side effects
How long do Celexa side effects last?
Most early side effects, like nausea, headache and jitteriness, ease within about two to four weeks. Some, including sexual changes, sweating and tiredness, can last for months. If a side effect still bothers you after the first month, talk to your prescriber. A dose adjustment, a change in timing or a different medicine may help.
What is the most common side effect of Celexa?
Nausea. In FDA trials, it affected 21% of people on Celexa versus 14% on placebo. It is also the top reason people stopped early. Dry mouth (20%) and sleepiness (18%) were close behind. Taking your dose with food is a simple first step to ask about.
Can Celexa make anxiety worse at first?
Yes, for some people. Anxiety (4% vs 3%) and agitation (3% vs 1%) were slightly more common on Celexa in trials, usually early on. Mild jitters often settle. Severe restlessness, panic or new dark thoughts need a same-day call to your prescriber, and 988 is available by call or text in a crisis.
Is it safe to take ibuprofen with Celexa?
Ask your pharmacist first. NSAIDs like ibuprofen and naproxen, along with aspirin, add to the bleeding risk from SSRIs, especially with regular use or in older adults. Many people use acetaminophen instead for occasional pain, but your pharmacist can check your full medication list and health history.
Why is the Celexa dose limited to 20 mg for people over 60?
Older adults clear citalopram more slowly, so the same dose produces higher blood levels. Higher levels mean more QT lengthening on the heart tracing. Since 2012, the FDA has set 20 mg a day as the maximum for adults over 60, people with liver impairment and CYP2C19 poor metabolizers.
The bottom line on Celexa side effects
Celexa side effects follow a fairly predictable calendar. The first week brings nausea, dry mouth and sleepiness. Weeks two to four usually bring relief from the stomach effects, sometimes with new sexual changes. By months two to six, what is left is mostly what lasts. Serious reactions are rare, but it pays to know them: a racing or irregular heartbeat, signs of serotonin syndrome, confusion that could mean low sodium, unusual bleeding, sudden eye pain, or any darkening of mood. If you are over 60, have liver problems or know you are a CYP2C19 poor metabolizer, ask whether 20 mg is your ceiling. Keep a short symptom log for the first month and bring it to your follow-up.
Medical disclaimer: This article is for general information only and is not a substitute for advice from your doctor, psychiatrist or pharmacist. Do not start, stop or change the dose of any medicine without talking to your prescriber. If you are thinking about suicide, call or text 988 (US). For a medical emergency, call 911.
