In general, serious side effects from omeprazole are rare in children when it’s prescribed appropriately and monitored by a clinician.
Common, non-serious side effects kids may have include headaches, nausea, vomiting, diarrhea, and abdominal pain. Serious adverse events are uncommon but can occur. Seek medical attention right away if you notice any of the following:
- Signs of a severe allergic reaction: swelling of the face or lips, hives, trouble breathing or swallowing.
- Jaundice or dark urine, pale stools, severe abdominal pain, or persistent vomiting (possible liver problems).
- Severe or persistent diarrhea, especially if it’s bloody or accompanied by fever (possible C. difficile infection).
- Confusion, muscle cramps, weakness, seizures (possible low magnesium).
- Unexplained fractures or bone pain with long-term, high-dose use (bone health concerns).
- New kidney problems: changes in urination, swelling, or blood in the urine.
- Easy bruising or unusual bleeding (if taking other medicines that affect bleeding).
Also note potential interactions with other medicines (e.g., certain antifungals, clopidogrel, some drugs for HIV or seizures). Tell your child’s doctor about all medicines and supplements.
If you’re worried about side effects, or if the child has ongoing symptoms, contact the prescribing clinician. This answer isn’t a substitute for professional medical advice—especially if your child has a fever, is vomiting, or has signs of an allergic reaction. If it’s an emergency, seek immediate medical care. If you’d like, tell me your child’s age, dose, duration of treatment, and any other meds, and I can tailor the info further.