Yes — Tums (calcium carbonate) and omeprazole work differently and are commonly used together, but space them apart, follow the label dose, and ask your pharmacist.
They act by different mechanisms, so they don't compete: Tums (calcium carbonate) is an antacid that neutralizes acid already in your stomach for fast, short-lived relief, while omeprazole is a proton-pump inhibitor that lowers how much acid your stomach makes over time. The FDA Prilosec OTC label notes omeprazole is "not intended for immediate relief" of heartburn and may take 1 to 4 days for full effect — which is why an antacid is often used for breakthrough symptoms in the meantime. None of the cited FDA, NHS, or MedlinePlus pages flags taking omeprazole alongside an antacid as a dangerous interaction. This is general information, not a substitute for advice from your own pharmacist or doctor.
Separate the timing: MedlinePlus advises not to take calcium carbonate within 1 to 2 hours of other medicines because the calcium can reduce how well the other drug is absorbed — so take your Tums a couple of hours apart from your omeprazole dose, and don't exceed the Tums label dose. Use Tums only for occasional breakthrough relief, not as a daily long-term combo without medical advice. Stop and call a doctor or pharmacist if heartburn continues or worsens, lasts more than 14 days on omeprazole, you've had heartburn over 3 months, or you have warning signs the Prilosec OTC label lists — trouble or pain swallowing, vomiting blood, black or bloody stools, or chest or shoulder pain — as these can signal a more serious problem. If you take other regular medicines, check with your pharmacist first: the NHS notes omeprazole itself can interact with drugs including clopidogrel, warfarin, digoxin, and phenytoin.
This is general reference, not medical advice, and not a guarantee of safety. Interactions depend on your doses, health conditions, and other medicines. Always confirm with your pharmacist or doctor before combining products, and follow the dosing on each label.