The most common side effects of Lexapro (escitalopram) are nausea, headache, insomnia, drowsiness, and diarrhea. In clinical trials, roughly two-thirds of people taking the standard 10 mg dose experienced at least one side effect, though most were mild and faded within the first few weeks of treatment.
The Most Frequent Side Effects
In placebo-controlled clinical trials, six side effects occurred in 10% or more of people taking Lexapro:
- Headache: up to 24%
- Nausea: up to 18%
- Insomnia: up to 14%
- Diarrhea: up to 14%
- Ejaculation disorder (in men): up to 14%
- Drowsiness: up to 13%
Other commonly reported effects include dry mouth, dizziness, constipation, and fatigue. These numbers come from controlled studies, so they reflect the difference between the drug and a placebo, which helps separate genuine drug effects from symptoms people experience regardless of treatment.
Why Lexapro Causes Nausea and Stomach Issues
Nausea is often the side effect people notice first, and it has a straightforward biological explanation. About 95% of your body’s serotonin is found in the gut, not the brain. Lexapro works by blocking the recycling of serotonin, which raises serotonin levels everywhere in the body, including the digestive tract. That extra serotonin activates receptors on nerve endings lining the stomach and intestines, which send signals to the brain’s vomiting center. The result is nausea, and sometimes diarrhea or loss of appetite.
Taking Lexapro with food can help blunt these effects. For most people, the nausea improves noticeably within one to two weeks as the body adjusts to the higher serotonin levels.
What the First Few Weeks Feel Like
Side effects tend to be most noticeable in the first week of treatment. Nausea, diarrhea, drowsiness, and decreased appetite are especially common early on and typically mild at lower starting doses. Your body needs days to weeks to fully adjust to the medication, so many of these effects diminish on their own without any change in dose.
The therapeutic benefits of Lexapro, reduced anxiety or improved mood, generally take two to four weeks to become apparent. This means there’s an awkward window where you may feel side effects before you feel the benefits. Knowing that timeline can make it easier to push through the adjustment period.
Dose Matters
Side effects are clearly dose-dependent. In clinical trials, 66% of people on 10 mg per day reported at least one side effect, compared to 86% of those on 20 mg per day. Specific effects like insomnia, diarrhea, dry mouth, dizziness, constipation, and fatigue were all more likely at the higher dose. This is one reason most prescribers start at 10 mg and only increase if needed.
Sexual Side Effects
Sexual side effects are among the most common reasons people consider stopping Lexapro. In men, ejaculation problems affected up to 14% of participants in trials. In women, research estimates that roughly 30% to 34% experience some form of sexual difficulty, including reduced desire, trouble with arousal, or difficulty reaching orgasm.
These effects tend to persist for as long as you’re taking the medication, unlike nausea or headache, which usually fade. If sexual side effects are significantly affecting your quality of life, dose adjustments or switching medications are options worth discussing. Among SSRIs, Lexapro actually has a somewhat lower rate of sexual dysfunction compared to some alternatives like fluoxetine (Prozac), where rates in women reached 55% in one comparative study.
Weight Changes
Weight gain on Lexapro is real but modest. Data from Harvard Health Publishing found that people taking escitalopram gained an average of 1.4 pounds over six months. That’s less dramatic than many people fear, but weight changes can add up over longer-term use. Some people also experience decreased appetite in the first weeks, which may cause slight weight loss before any gain occurs.
Rare but Serious Reactions
Most side effects from Lexapro are uncomfortable, not dangerous. But there are two serious risks to be aware of.
Serotonin Syndrome
Serotonin syndrome occurs when serotonin levels climb dangerously high, usually because Lexapro is combined with another medication that also raises serotonin. This includes certain migraine drugs, pain medications, herbal supplements like St. John’s wort, and other antidepressants. Symptoms appear within minutes to hours and include agitation, rapid heartbeat, high blood pressure, fever, heavy sweating, muscle spasms, tremor, and loss of coordination. Confusion and hallucinations can occur in severe cases. This is a medical emergency.
Serotonin syndrome is rare when Lexapro is taken on its own at prescribed doses. The risk comes primarily from drug interactions, which is why it’s important to tell your prescriber about every medication and supplement you take.
Suicidality Risk in Young Adults
Lexapro carries an FDA boxed warning about an increased risk of suicidal thoughts and behavior in children, adolescents, and young adults (ages 18 to 24) during the early weeks of treatment. This warning applies to all antidepressants, not just Lexapro. In adults over 24, clinical trials did not show this increased risk. In adults 65 and older, antidepressants were actually associated with a reduced risk compared to placebo.
Stopping Lexapro Safely
Lexapro carries a moderate risk of discontinuation syndrome if you stop abruptly. Symptoms typically begin two to four days after your last dose and can include dizziness, nausea, fatigue, headache, irritability, vivid or disturbing dreams, and a distinctive sensation often described as “brain zaps,” a brief electric shock-like feeling in the head. Anxiety, agitation, and flu-like achiness are also common.
These symptoms are not a sign of addiction. They happen because your brain needs time to readjust to functioning without the drug’s serotonin-boosting effect. Gradually reducing the dose over weeks, rather than stopping cold turkey, significantly reduces or eliminates these effects. The tapering schedule varies from person to person, so it’s something to plan with your prescriber rather than attempt on your own.