What the label lists and what reports show
Omeprazole side effects
Omeprazole's FDA label: “Most common adverse reactions in adults (incidence ≥2%) are Headache, abdominal pain, nausea, diarrhea, vomiting, and flatulence.” FAERS holds 446,179 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is chronic kidney disease (36,748 reports).
- Generic listed
- A presentation discontinued
Check it at the source: the omeprazole FDA label on DailyMed (effective April 22, 2024, Apotex Corp); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of omeprazole delayed-release capsules?Omeprazole can cause serious side effects, including: See “What is the most important information I should know about omeprazole?” Vitamin B-12 deficiency. Omeprazole delayed-release capsules reduces the amount of acid in your stomach. Stomach acid is needed to absorb vitamin B-12 properly. Talk with your doctor about the possibility of vitamin B-12 deficiency if you have been on omeprazole delayed-release capsules for a long time (more than 3 years). Low magnesium levels in your body. This problem can be serious. Low magnesium can happen in some people who take a PPI medicine for at least 3 months. If low magnesium levels happen, it is usually after a year of treatment. You may or may not have symptoms of low magnesium. […]
Source: FDA drug label, Apotex Corp, effective April 22, 2024 (SPL set b83329ac-a65e-b3af-a3fb-c5a6c740e5e7), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions in adults (incidence ≥2%) are Headache, abdominal pain, nausea, diarrhea, vomiting, and flatulence.
From the label: adverse reactions, continuedAdults: Most common adverse reactions in adults (incidence ≥2%) are Headache, abdominal pain, nausea, diarrhea, vomiting, and flatulence. ( 6 ) Pediatric patients (1 to 16 years of age): Safety profile similar to that in adults, except that respiratory system events and fever were the most frequently reported reactions in pediatric studies. ( 8.4 ) To report SUSPECTED ADVERSE REACTIONS, contact Apotex Corp. at 1-800-706-5575 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. The following serious adverse reactions are described below and elsewhere in labeling: Acute Tubulointerstitial Nephritis [see Warnings and Precautions ( 5.2 )] Clostridium difficile-Associated Diarrhea [see Warnings and Precautions ( 5.3 )] Bone Fracture [see Warnings and Precautions ( 5.4 )] Cutaneous and Systemic Lupus Erythematosus [see Warnings and Precautions ( 5.6 )] Cyanocobalamin (Vitamin B-12) Deficiency [see Warnings and Precautions ( 5.8 )] Hypomagnesemia [see Warnings and Precautions ( 5.9 )] Fundic Gland Polyps [see Warnings and Precautions ( 5.13 )] 6.1 Clinical Trials Experience with Omeprazole Monotherapy Monotherapy Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. …
Source: FDA drug label, Apotex Corp, effective April 22, 2024 (SPL set b83329ac-a65e-b3af-a3fb-c5a6c740e5e7), via openFDA; the full label on DailyMed
What do FAERS reports show?
446,179 reports list omeprazole among the medicines taken, each a report of something that happened, not proof the medicine caused it; 39,203 are coded as a death and 150,196 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 22 reactions below, 11 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Omeprazole: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions