Given the vast number of people taking or being prescribed omeprazole, a doctor has sounded a cautionary note to anyone using it. "They reduce stomach acid and are useful, but not always," she stated. View 4 Images Dr Ana Pérez Ballesta has discussed the risks of taking omeprazole unnecessarily (stock image) (Image: Getty)Unnecessary prolonged use can have significant consequences. How much to take and for how long depends on the type of omeprazole you're taking and why you're taking it. Like all medications, omeprazole can lead to side effects, although not everyone experiences them.