Common possible side effects with Seroquel XR include:

• Drowsiness
• Dry mouth
• Constipation
• Dizziness
• Increased appetite
• Upset stomach
• Weight gain
• Fatigue
• Disturbance in speech and language
• Stuffy nose

Seroquel XR may cause serious side effects, including:

• Risk of death in the elderly with dementia
• Risk of suicidal thoughts or actions
• High blood sugar (hyperglycemia)
• High fat levels in your blood (increased cholesterol and triglycerides)
• Weight gain
• Neuroleptic malignant syndrome (NMS): NMS is a rare but very serious condition that can happen in people who take antipsychotic medicines, including Seroquel XR. NMS can cause death and must be treated in a hospital. Call your doctor right away if you become severely ill and have some or all of these symptoms:
• High fever
• Excessive sweating
• Rigid muscles
• Confusion
• Changes in your breathing, heartbeat, and blood pressure
• Tardive dyskinesia: Tell your healthcare provider about any movements you cannot control in your face, tongue, or other body parts. These may be signs of a serious condition. Tardive dyskinesia may not go away, even if you stop taking Seroquel XR. Tardive dyskinesia may also start after you stop taking Seroquel XR.
• Orthostatic hypotension (decreased blood pressure): lightheadedness or fainting caused by a sudden change in heart rate and blood pressure when rising too quickly from a sitting or lying position.
• Increases in blood pressure: reported in children and teenagers. Your healthcare provider should check blood pressure in children and adolescents before starting Seroquel XR and during therapy. Seroquel XR is not approved for patients under 18 years of age.
• Low white blood cell count
• Cataracts
• Seizures
• Abnormal thyroid tests: Your healthcare provider may do blood tests to check your thyroid hormone level.
• Increases in prolactin levels: Your healthcare provider may do blood tests to check your prolactin levels.
• Increases in liver enzymes: Your healthcare provider may do blood tests to check your liver enzyme levels.
• Long lasting and painful erection
• Difficulty swallowing