One capsule of omeprazole a day is generally not very harmful if taken for a short period of time as directed by a doctor. However, if taken for a long period of time, it has some potential side effects, which may include affecting the absorption of micronutrients, increasing the risk of gastric carcinoid tumor, stomach cancer, bone fracture, intestinal infection, pneumonia, cardiovascular and cerebrovascular events and even chronic kidney disease (CKD) and dementia. 1. Omeprazole is a proton pump inhibitor mainly used in the treatment of gastrointestinal diseases such as gastric ulcer, duodenal ulcer, reflux esophagitis, stress ulcer, etc. It is able to inhibit the secretion of gastric acid and reduce the irritation to gastric mucosa. Usually, it needs to be taken daily under doctor’s instruction. 2. However, Omeprazole should not be taken for a long period of time. The potential side effects of long-term application of PPIs may include affecting the absorption of micronutrients, increasing the risk of gastric carcinoid tumors, gastric cancer, bone fracture, intestinal-origin infections, pneumonia, cardio-cerebral and cerebral vascular events and even chronic kidney disease (CKD) and dementia. That is why any drug is not recommended for long-term application without indications for its use. If the use of omeprazole causes significant discomfort, the drug should be discontinued and hospitalized.