Seroquel (quetiapine) is an atypical antipsychotic prescribed for schizophrenia, bipolar disorder, and major depressive disorder. Its most common side effects are drowsiness, dizziness, and dry mouth, but it also carries risks for weight gain, metabolic changes, and movement disorders that are important to understand before starting or continuing the medication.
The Most Common Side Effects
Drowsiness is the single most reported side effect. In clinical trials of over 700 patients, 18% experienced significant sleepiness when taking Seroquel alone, compared to 8% on placebo. When Seroquel was added on top of another mood stabilizer, that number jumped to 34%. This sedation is so pronounced that some prescribers use low doses of quetiapine specifically as a sleep aid, though it was never approved for that purpose.
Dizziness affects about 11% of users, and dry mouth about 9%. Both are noticeably more common than in people taking a placebo. Other frequently reported effects include constipation, increased appetite, and a drop in blood pressure when standing up quickly, which can cause lightheadedness or faintness. Most of these effects are strongest in the first few weeks and may lessen as your body adjusts.
Weight Gain and Metabolic Changes
Seroquel can increase appetite and lead to meaningful weight gain over time. This isn’t just cosmetic. The medication can raise blood sugar levels and shift cholesterol and triglyceride numbers in unhealthy directions. These metabolic changes increase the risk of developing type 2 diabetes and cardiovascular problems, particularly with long-term use.
Because of these risks, monitoring guidelines recommend checking blood sugar about four months after starting the medication and then at least once a year. Cholesterol panels follow the same schedule. Body weight should be tracked monthly for the first six months and then every three months once the dose is stable. If you notice rapid weight gain or increased thirst and urination (signs of rising blood sugar), those are worth bringing up promptly.
Effects on Hormones
All antipsychotics can raise prolactin, a hormone involved in breast milk production. Elevated prolactin can cause missed periods, breast tenderness or discharge, and reduced sex drive in both men and women. The good news is that quetiapine raises prolactin less frequently than some other antipsychotics, particularly risperidone. It binds to dopamine receptors in a more targeted way, which reduces this particular hormonal disruption. Still, it can happen, and symptoms sometimes go unrecognized because people don’t connect them to the medication.
Heart Rhythm Concerns
Seroquel can slightly lengthen the electrical cycle of your heartbeat, measured as the QT interval on an EKG. In a study of nearly 9,000 patients, the average increase was about 8 milliseconds. For most people, this is clinically insignificant. The risk becomes more relevant if you already have a heart rhythm disorder, take other medications that affect the QT interval, or have low potassium or magnesium levels. Your prescriber may want a baseline EKG before starting the medication if any of these apply.
Tardive Dyskinesia
Tardive dyskinesia (TD) is a movement disorder that causes involuntary, repetitive movements, most often of the face, tongue, and jaw. It can develop after months or years of antipsychotic use and sometimes persists even after stopping the medication. A large U.S. study estimated that roughly 1 to 2% of people taking antipsychotics develop TD per year. Quetiapine was the most commonly prescribed antipsychotic among TD cases in that study, though that partly reflects how widely it is prescribed overall. The risk increases with age, higher doses, and longer duration of use.
Risks for Older Adults
Seroquel carries a boxed warning, the FDA’s most serious safety alert, regarding elderly patients with dementia-related psychosis. An analysis of 17 placebo-controlled trials found that older adults with dementia who took atypical antipsychotics had 1.6 to 1.7 times the risk of death compared to those on placebo. In concrete terms, the death rate was about 4.5% over a 10-week trial period, versus 2.6% on placebo. Most deaths were cardiovascular (heart failure, sudden death) or infectious (pneumonia). Seroquel is not approved for treating dementia-related behavioral symptoms, and this warning applies to the entire class of atypical antipsychotics.
Side Effects in Children and Teens
Children and adolescents taking Seroquel can experience the same side effects as adults, with a few additional concerns. Increased blood pressure has been noted specifically in younger patients. Weight gain and metabolic effects can be more pronounced in this age group because their bodies are still developing. Pediatric patients also need closer monitoring for suicidal thoughts, particularly in the early weeks of treatment or after dose changes.
What Happens When You Stop
Stopping Seroquel abruptly can trigger withdrawal symptoms including headaches, nausea, dizziness, diarrhea, vomiting, irritability, and insomnia. In more severe cases, people experience hallucinations, rapid weight changes, or shortness of breath. The timeline depends on how long you’ve been taking it and at what dose. If you’ve used it for fewer than 12 weeks, symptoms typically last a few days to a couple of weeks. For people who’ve taken it longer than 12 weeks, withdrawal can stretch to about three weeks. Tapering the dose gradually, rather than stopping all at once, significantly reduces these effects.
Dose Matters
Many of Seroquel’s side effects are dose-dependent. At lower doses (25 to 100 mg), drowsiness and some blood pressure effects tend to dominate. At higher doses used for schizophrenia or mania (400 to 800 mg), metabolic effects, weight gain, and hormonal changes become more significant. This is worth understanding because the same drug at 50 mg for sleep creates a very different side effect profile than at 600 mg for psychosis. If side effects are bothering you, a dose adjustment is often the first thing to explore before switching medications entirely.