Sertraline, sold as Zoloft, causes side effects in most people during the first few weeks of treatment. The most common ones, including nausea, headache, and sleep changes, typically fade within the first month as your body adjusts. Others, like sexual difficulties and weight changes, can persist longer. Here’s what to expect across the short and long term.
Early Side Effects and When They Ease Up
The side effects most people notice first are gastrointestinal: nausea, diarrhea, and stomach discomfort. These tend to start within days of your first dose or a dose increase. For most people, they diminish noticeably by the end of the first month. In clinical studies, reports of these effects in people taking sertraline daily didn’t differ from placebo by the third month of treatment.
Other common early side effects include headache, dizziness, fatigue, dry mouth, and sweating. Sleep disruption is also typical. Some people experience insomnia, while others feel unusually drowsy. These effects generally follow the same pattern: worst in the first week or two, then gradually tapering off.
A few practical things help with nausea specifically. Taking sertraline with food makes a noticeable difference. Eating smaller, more frequent meals throughout the day, staying hydrated, and sucking on hard candy can also help. If nausea is severe or doesn’t let up after a couple of weeks, your prescriber can adjust the dose or switch to a slow-release form.
Sexual Side Effects
Sexual difficulties are among the most common reasons people consider stopping sertraline, and unlike nausea, they don’t always resolve on their own. The effects span the full range of sexual function: reduced desire, difficulty reaching orgasm, erectile dysfunction, and sometimes genital numbness. Both men and women are affected, though the specific symptoms differ.
These side effects are also significantly underreported. Many people don’t bring them up with their doctor, and clinicians don’t always ask. The true prevalence is hard to pin down for that reason, but it’s well established that sertraline is one of the SSRIs most commonly linked to sexual dysfunction. In the vast majority of cases, sexual function returns to normal after stopping the medication. Persistent sexual dysfunction after discontinuation has been reported but is considered rare.
Weight Changes Over Time
Sertraline has a modest effect on weight, but it grows over time. At six months of use, the average weight gain is less than half a pound, which is essentially unnoticeable. By two years, though, the average climbs to about 3.2 pounds. That’s a population average, meaning some people gain more and others gain nothing at all or even lose weight initially (appetite suppression can be an early side effect).
Compared to other antidepressants, sertraline sits on the lower end of the weight gain spectrum. If you’re tracking your weight while on sertraline, gradual changes over months are more typical than sudden shifts.
Mental Health Effects in Younger Adults
Sertraline carries the FDA’s strongest safety warning, a boxed warning, about the risk of increased suicidal thoughts and behaviors in people under 25. This applies to all antidepressants, not just sertraline. In pooled data from trials involving over 77,000 adults and 4,500 children, the risk broke down by age:
- Under 18: 14 additional cases of suicidal thoughts per 1,000 patients treated, compared to placebo
- 18 to 24: 5 additional cases per 1,000 patients
- 25 to 64: 1 fewer case per 1,000 patients (protective effect)
- 65 and older: 6 fewer cases per 1,000 patients (stronger protective effect)
The risk is highest in the first few months of treatment and during dose changes. This doesn’t mean sertraline causes suicidal behavior in most young people who take it. It means the early weeks require closer monitoring, particularly for new or worsening agitation, irritability, or dark thoughts that feel different from the depression being treated. Family members and close contacts should also be aware of what to watch for during this window.
Low Sodium in Older Adults
For people over 65, one underappreciated risk is hyponatremia, a drop in blood sodium levels. Symptoms include confusion, headache, nausea, and in severe cases, seizures. It can mimic a worsening of depression or look like general malaise, which makes it easy to miss.
The risk is highest in the first month. In a study of patients with a mean age of 76, new users of sertraline (those within the first 30 days) had five times the odds of developing hyponatremia compared to non-users. After about three months, that elevated risk dropped to near baseline. This is one reason prescribers sometimes check blood sodium levels early in treatment for older patients.
What Happens When You Stop
Sertraline carries a moderate risk of discontinuation syndrome, a cluster of symptoms that can appear two to four days after stopping the medication abruptly. These include flu-like feelings (fatigue, headache, achiness, sweating), nausea, dizziness, burning or shock-like sensations in the body, vivid dreams, and mood changes like irritability or anxiety.
This isn’t the same as a relapse of depression. Discontinuation syndrome is your body readjusting to the absence of the drug, and it typically resolves within a few weeks. The most reliable way to avoid it is to taper slowly rather than stopping cold. If symptoms do appear, resuming the previous dose usually resolves them within 24 hours, and then a more gradual taper can begin. How long tapering takes varies from person to person. There’s no universal timeline, so your prescriber will adjust the schedule based on how you respond.
Serotonin Syndrome
Serotonin syndrome is a rare but potentially dangerous reaction that happens when serotonin levels build up too high. It’s most likely when sertraline is combined with other medications that also raise serotonin, including certain migraine drugs, pain medications, supplements like St. John’s wort, and other antidepressants.
The symptoms fall into three categories. Neuromuscular signs include tremor, twitching, and exaggerated reflexes. Autonomic signs include rapid heart rate, blood pressure swings, and fever. Mental status changes include agitation, confusion, and in severe cases, delirium. These symptoms typically come on quickly, within hours rather than days, and represent a medical emergency. If you’re taking sertraline and notice a rapid onset of these symptoms, especially after adding a new medication, seek immediate medical attention.
Heart Rhythm Safety
Some medications in the SSRI class have been flagged for affecting heart rhythm, specifically a measurement called the QT interval. Sertraline, at standard doses, does not appear to carry a meaningful risk here. Multiple studies, including research in patients recovering from heart events, have found no clinically significant QT prolongation with sertraline. Among SSRIs, it’s considered one of the lower-risk options for heart rhythm effects.