Red flags — call us immediately or go to the Emergency Department if:
- Your baby is unusually drowsy or hard to rouse for feeds (infant sedation)
- Your baby is not gaining weight normally
- You notice changes in your mood, sleep, or thinking (contact your mental health team today)
- You feel thoughts of hurting yourself or your baby (call 112 immediately)
- You stopped olanzapine suddenly and feel very unwell
- A rash that does NOT fade when you press a clear glass on it — sepsis sign
- Fever in a baby under 3 months (any temperature ≥ 38.0 °C)
- Fast breathing, blue lips, or sucking-in of the ribs — breathing emergency
- A fit/seizure, or your child becomes floppy or unresponsive — general red flag
What olanzapine is
Olanzapine (Zyprexa) is an atypical antipsychotic medicine. Doctors prescribe it for schizophrenia, bipolar disorder, and postpartum psychosis. It is also sometimes used at low doses for agitation. In the postpartum period, it is a key medicine for mothers with serious psychiatric conditions where relapse could be dangerous for both mother and baby.
How much passes into breast milk
Olanzapine does pass into breast milk. Studies estimate the relative infant dose at about 1–2 % of the mother's weight-adjusted daily dose — which is low. However, some published case reports describe breastfed babies with unusual drowsiness or slower weight gain when their mothers were taking olanzapine. This means careful monitoring of your baby is important.
What current guidance says
LactMed and Hale's Medications and Mothers' Milk list olanzapine as probably compatible with breastfeeding with monitoring for infant sedation and weight gain. The UK Drugs in Breastmilk Information Service concurs. The Belgian AFMPS SmPC advises caution but does not prohibit breastfeeding. Specialists generally consider olanzapine an acceptable choice during breastfeeding when the psychiatric indication is strong. Never change your dose without your psychiatrist's advice.
What to watch for in your baby
Watch for unusual drowsiness, difficulty rousing your baby for feeds, poor feeding, or slower weight gain. These signs are not common, but they have been reported. If you notice them, contact your GP or paediatrician — they may want to check your baby's weight and monitor for a period. Premature babies need extra attention.
Your mental health comes first
Olanzapine is often prescribed because the risk of not treating your condition is high. Postpartum psychosis and bipolar episodes can escalate quickly and are medical emergencies. Do not stop olanzapine without talking to your psychiatrist. If you feel your symptoms returning — changes in mood, reduced sleep, or unusual thoughts — contact your mental health team immediately.
If anything changes
Watch your baby for unusual drowsiness or poor weight gain. Never stop olanzapine without your psychiatrist's guidance. If you ever have thoughts of harming yourself or your baby, call 112 immediately.
Emergency? Call 112. Do not wait for a reply from us.
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Message us on WhatsAppReviewed and signed off by Dr Didier Decamps on 5 September 2026. This is general information and does not replace an individual assessment by a qualified clinician.
Written with AI assistance. Reviewed, corrected and signed by Dr Didier Decamps, paediatrician.
Last reviewed: 5 September 2026