What the label lists and what reports show
Olanzapine side effects
Olanzapine's FDA label: “Most common adverse reactions (≥5% and at least twice that for placebo) associated with: Oral Olanzapine Monotherapy: Schizophrenia (Adults) – postural hypotension, constipation, weight gain, dizziness, personality disorder, akathisia.” FAERS holds 107,881 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is weight increased (6,861 reports).
- Generic listed
- Boxed warning
Check it at the source: the olanzapine FDA label on DailyMed (effective March 5, 2026, Macleods Pharmaceuticals Limited); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of olanzapine tablets?Serious side effects may happen when you take olanzapine tablets, including: • See “What is the most important information I should know about olanzapine tablets?”, which describes the increased risk of death in elderly people with dementia-related psychosis and the risks of high blood sugar, high cholesterol and triglyceride levels, and weight gain. • Increased incidence of stroke or “mini-strokes” called transient ischemic attacks (TIAs) in elderly people with dementia-related psychosis (elderly people who have lost touch with reality due to confusion and memory loss). Olanzapine tablets are not approved for these patients. • Neuroleptic Malignant Syndrome (NMS): NMS is a rare but very serious condition that can happen in people who take antipsychotic medicines, including olanzapine tablets. NMS can cause death and must be treated in a hospital. […]
Source: FDA drug label, Macleods Pharmaceuticals Limited, effective March 5, 2026 (SPL set 8e095987-bdea-42f2-9550-c7155cf07d30), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (≥5% and at least twice that for placebo) associated with: Oral Olanzapine Monotherapy: Schizophrenia (Adults) – postural hypotension, constipation, weight gain, dizziness, personality disorder, akathisia.
Table 12: Percentage of Patients from a Schizophrenia Trial with Treatment-Emergent…
| Reaction | Placebo (N=68) | Olanzapine 5 ± 2.5 mg/day (N=65) | Olanzapine 10 ± 2.5 mg/day (N=64) | Olanzapine 15 ± 2.5 mg/day (N=69) |
|---|---|---|---|---|
| Asthenia | 15 | 8 | 9 | 20 |
| Dry mouth | 4 | 3 | 5 | 13 |
| Nausea | 9 | 0 | 2 | 9 |
| Somnolence | 16 | 20 | 30 | 39 |
| Tremor | 3 | 0 | 5 | 7 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedWhen using olanzapine and fluoxetine in combination, also refer to the Adverse Reactions section of the package insert for Symbyax. Most common adverse reactions (≥5% and at least twice that for placebo) associated with: Oral Olanzapine Monotherapy: Schizophrenia (Adults) – postural hypotension, constipation, weight gain, dizziness, personality disorder, akathisia. ( 6.1 ) Schizophrenia (Adolescents) – sedation, weight increased, headache, increased appetite, dizziness, abdominal pain, pain in extremity, fatigue, dry mouth. ( 6.1 ) Manic or Mixed Episodes, Bipolar I Disorder (Adults) – asthenia, dry mouth, constipation, increased appetite, somnolence, dizziness, tremor. ( 6.1 ) Manic or Mixed Episodes, Bipolar I Disorder (Adolescents) – sedation, weight increased, increased appetite, headache, fatigue, dizziness, dry mouth, abdominal pain, pain in extremity. ( 6.1 ) Combination of Olanzapine and Lithium or Valproate: Manic or Mixed Episodes, Bipolar I Disorder (Adults) – dry mouth, weight gain, increased appetite, dizziness, back pain, constipation, speech disorder, increased salivation, amnesia, paresthesia. ( 6.1 ) Olanzapine and Fluoxetine in Combination: Also refer to the Adverse Reactions section of the package insert for Symbyax.
Source: FDA drug label, Macleods Pharmaceuticals Limited, effective March 5, 2026 (SPL set 8e095987-bdea-42f2-9550-c7155cf07d30), via openFDA; the full label on DailyMed
What do FAERS reports show?
107,881 reports list olanzapine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 13,264 are coded as a death and 47,549 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 18 reactions below, 13 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Olanzapine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions