The worst side effects of citalopram include heart rhythm changes at higher doses, serotonin syndrome, increased suicidal thoughts in younger adults, dangerously low sodium levels, and seizures. These serious reactions are uncommon, but they represent real risks that distinguish citalopram from many other antidepressants. Most people taking citalopram experience only mild side effects like nausea or drowsiness, but knowing the severe ones helps you recognize warning signs early.
Heart Rhythm Changes
Citalopram can lengthen the electrical cycle that controls your heartbeat, a measurement called the QT interval. When this interval stretches too far, it raises the risk of a dangerous irregular heart rhythm called Torsades de Pointes, which can cause fainting, cardiac arrest, or death. This risk is dose-dependent, which is why the maximum dose of citalopram is capped at 40 mg per day.
For people over 60, those with liver problems, or those taking certain other medications that slow how the body processes citalopram (like omeprazole), the maximum drops to 20 mg per day because the drug builds up to higher levels in their blood. Symptoms to watch for include chest pain, shortness of breath, dizziness, fainting, or feeling like your heart is racing or skipping beats. If you notice any of these, it’s a situation that needs immediate medical attention.
Suicidal Thoughts in Younger Adults
Citalopram carries the FDA’s strongest safety warning, a black box warning, about increased suicidal thinking and behavior in people under 25. In clinical trials, children and teenagers taking antidepressants had 14 additional cases of suicidal thoughts per 1,000 patients compared to placebo. For adults aged 18 to 24, that number was 5 additional cases per 1,000.
The risk is highest during the first few months of treatment and when doses change. Importantly, adults over 25 did not show this increased risk. In fact, adults 65 and older had 6 fewer cases of suicidal thinking per 1,000 patients compared to those taking a placebo, suggesting the medication was protective in that age group. Warning signs include new or worsening depression, extreme agitation, panic attacks, aggressive behavior, severe restlessness, or insomnia that wasn’t there before.
Serotonin Syndrome
Serotonin syndrome happens when too much serotonin accumulates in the body, usually because citalopram is combined with another drug that also raises serotonin levels. This includes certain migraine medications, pain relievers, herbal supplements like St. John’s wort, and other antidepressants. The condition can range from mild to life-threatening.
Diagnosis requires at least three of the following: agitation, heavy sweating, fever, confusion, muscle spasms, overactive reflexes, shivering, tremor, abnormal eye movements, or uncoordinated movements. In its most severe form, serotonin syndrome can cause high fever, seizures, and coma. Symptoms typically develop within hours of a dose change or adding a new medication. This is a medical emergency that requires immediate treatment.
Low Sodium Levels
Citalopram can cause the body to retain too much water relative to sodium, diluting sodium levels in the blood. This is most dangerous in older adults, particularly women with low body weight or already-low baseline sodium. Chronic kidney disease, heart failure, diabetes, and hypothyroidism all compound the risk. Taking multiple medications further raises the likelihood.
Mild cases cause headache, nausea, and difficulty concentrating. Severe drops in sodium lead to confusion, unsteadiness, memory problems, and in extreme cases, seizures or coma. Because the symptoms can look like general unwellness or even depression itself, low sodium often goes unrecognized until it becomes serious. This is one reason blood work is sometimes checked after starting the medication, especially in older patients.
Increased Bleeding Risk
Citalopram affects how platelets function, making bleeding more likely. On its own, this effect is usually minor. But if you’re also taking NSAIDs like ibuprofen or naproxen, the risk climbs significantly. A meta-analysis of 10 studies found a 75% increased risk of upper gastrointestinal bleeding when SSRIs and NSAIDs are used together. Unusual bruising, blood in your stool, or prolonged bleeding from cuts are signs to take seriously.
Seizures and Severe Allergic Reactions
Seizures are a rare but documented side effect of citalopram. The risk increases at higher doses or if you have a pre-existing seizure disorder. Severe allergic reactions, while also uncommon, can involve rash, hives, blistering skin, swelling of the face or throat, hoarseness, and difficulty breathing or swallowing. These require emergency care.
Citalopram can also trigger or worsen a form of glaucoma called angle-closure glaucoma, where fluid pressure builds rapidly inside the eye. Symptoms include sudden eye pain, nausea, seeing colored rings around lights, and redness or swelling in the eye. Left untreated, this can cause permanent vision loss.
Withdrawal From Stopping Too Quickly
While not a side effect of taking citalopram, withdrawal from stopping it abruptly is one of the most common problems people experience. Citalopram has a half-life of about 36 hours, meaning it clears your system within roughly a week. That’s fast enough for your brain to react to the sudden change in serotonin levels.
Withdrawal symptoms typically appear within days to weeks of stopping or sharply reducing the dose. The most distinctive ones are physical: dizziness, flu-like symptoms, numbness or tingling, sensitivity to sound, ringing in the ears, and “brain zaps,” a sensation people describe as brief electric shocks in the head. Anxiety and depression can also resurface or temporarily worsen. These symptoms are preventable by tapering the dose gradually rather than stopping all at once.
The severity of withdrawal varies widely. Some people taper off with little discomfort, while others find even slow reductions difficult. Longer duration of use and higher doses generally make withdrawal more challenging.