hello concerned elizabeth, Thanks for writing to Hcm I understand your query and know you are concerned with omeprazole side effects over long term. First of all,let me ask a few things: how old are you?why did you start omeprazole in the first place? do you have any other medical/drug history?? Coming to the query ,omeprazole 40mg a day is a normal dosage for heartburn,gastroeosphageal reflux disease etc. Normally omeprazole and other proton pump inhibitors have decent safety profile and very less side effects over short term like 3months regimens But since you are taking since 15 years, i would recommend the following tests for you, a complete blood count,serum calcium,magnesium and iron levels and Vitamin B12 levels. my advise is that first You should understand that omeprazole has minimal side effects in short term use,but over all over long term side effects like deficiency of iron,magnesium ,calcium and vitamin B12 has been seen in a few patients here The above mentioned tests i suggested would help to assess if you suffering any of the deficiency and those can be easily corrected by diet changes or supplements. So dont worry about it. such drugs very rarely cause pneumonia or diarrhoea ;both of which you dont have. So i would suggest you relax,and try to cut down omeprazole usage to 20mg a day,half an hour before the meal around which you feel maximum heartburn. i would also recommend you to try stopping omeprazole in a slow manner by reducing it from present 40mg to 20mg and then stopping it. If symptoms persists ,my advise would be take gelusil syrup twice daily for two weeks and If omeprazole is must ,go with 20mg once daily for two weeks and stop for a week and resume . Hope i clarified your doubts and hope it helps Followup if further advise needed. Relax ,take care and good day