Workup for 18-Year-Old Female with Abdominal Pain, Chronic Nausea, and Iron Deficiency on Omeprazole
This patient requires immediate testing for celiac disease and H. pylori, followed by consideration of bidirectional endoscopy, with strong attention to the omeprazole as a potential contributor to her iron deficiency.
Immediate Non-Invasive Testing
Test for celiac disease with serology (tissue transglutaminase antibodies with total IgA) as this is a critical cause of both iron deficiency and chronic nausea in young women, and all patients with iron deficiency anemia should be screened 1.
Test for H. pylori using non-invasive methods (stool antigen or urea breath test) before proceeding to endoscopy, as this can cause both iron deficiency and chronic nausea 1.
Address the Omeprazole Issue
Strongly consider discontinuing omeprazole as proton pump inhibitors are a documented cause of iron deficiency anemia through impaired iron absorption 2, 3, 4, 5, 6, 7.
The FDA label specifically warns that daily treatment with acid-suppressing medications over a long period (longer than 3 years) may lead to malabsorption of nutrients, and PPIs can cause iron deficiency 2.
Case reports demonstrate that iron deficiency anemia from PPIs may not respond to oral iron supplementation while the patient remains on the PPI, and anemia can take 2-8 months to correct after discontinuation 4, 5, 6.
If acid suppression is truly necessary, consider switching to an H2-receptor antagonist (like famotidine), which has been shown to allow resolution of PPI-induced iron deficiency 3.
Endoscopic Evaluation Decision
For this symptomatic premenopausal woman, bidirectional endoscopy should be performed if celiac disease and H. pylori testing are negative 1.
The AGA guidelines suggest bidirectional endoscopy over iron replacement alone for premenopausal women with iron deficiency anemia (conditional recommendation), but this is a symptomatic patient with chronic abdominal pain and nausea, which changes the calculus 1.
When patients have GI-related symptoms, testing including endoscopy should be tailored to the symptoms rather than following the asymptomatic algorithm 1.
The prevalence of GI malignancy is very low in this age group (0.9% for lower GI, 0.2% for upper GI), but other important diagnoses like peptic ulcer disease, erosive esophagitis, inflammatory bowel disease, and gastric/duodenal pathology can be detected 1.
Additional Workup Considerations
Verify iron deficiency with ferritin <45 ng/mL and hemoglobin <12 g/dL in this non-pregnant woman to confirm true iron deficiency anemia 1.
Assess for other causes of iron deficiency: detailed menstrual history (menorrhagia is common in this age group), dietary assessment (vegetarian/vegan diet), blood donation history, and NSAID use 1.
Check vitamin B12 levels as omeprazole can cause B12 deficiency with prolonged use, which could contribute to symptoms 2.
Iron Replacement Strategy
Do not expect adequate response to oral iron while on omeprazole - studies show only 16% of patients on omeprazole have normal hemoglobin response to oral iron 4.
If omeprazole cannot be discontinued immediately, consider intravenous iron therapy as oral iron absorption will be impaired 1, 4.
Once omeprazole is stopped, oral iron supplementation should be given once daily (not multiple times per day due to hepcidin response), preferably on an empty stomach or with vitamin C to enhance absorption 1.
Critical Pitfall to Avoid
Do not attribute the iron deficiency solely to menstrual loss or the omeprazole without completing the workup - dual pathology occurs in 1-10% of cases, and serious GI conditions can coexist with other causes of iron deficiency 1. The chronic nausea particularly warrants investigation for celiac disease, peptic ulcer disease, or other upper GI pathology beyond simple reflux.