The most common side effects of sertraline are nausea, upset stomach, loss of appetite, dry mouth, diarrhea, dizziness, sweating, drowsiness, and difficulty sleeping. More serious side effects can occur. These include unusual or numerous mood changes, change in sexual ability and interest, tremors, and unusual weight loss. Other serious side effects include bruising or bleeding easily, constant nausea or vomiting, stomach pain, black stools, seizures, urinary changes (dark colored or amount), jaundice, and vomit that looks like coffee grounds in appearance. You should talk to your doctor about these serious side effects. Get emergency care if you have an allergic reaction marked by facial and throat swelling, difficulty breathing, hives, and itchy rash.
Taking sertraline can lead to a serious medical condition known as serotonin syndrome. It may occur when taking other medications which work to increase serotonin (such as fentanyl, St. John's Wort, triptans, tramadol). Symptoms of serotonin syndrome include hallucinations, decreased coordination, restlessness, rapid heart rate, dizziness, fever, severe nausea, vomiting or diarrhea, and twitching muscles. Finally, there is an increased risk of suicidal behavior or thoughts when first taking an antidepressant.