Many patients that are prescribed iron report gastrointestinal side effects. This research project aims to investigate if the gastrointestinal symptoms of taking iron supplementation are related to changes in gases produced by bacteria in the gastrointestinal tract.

This study is a pre-post interventional, two armed prospective cohort study where patients who are newly diagnosed with iron deficiency anaemia are prescribed iron therapy (either oral iron supplements, 200mg capsules containing 65mg of iron 2-3 times daily, or intravenous iron 1000-1500mg) as part of their standard care. Participants will be asked to provide breath samples and complete the IBS-SSS questionnaire at baseline and after 4 weeks of taking the iron therapy as part of their standard care. A diary including stool consistency and frequency will also be completed by participants on a daily basis. For further exploratory research, some participants from each the oral and IV iron arm will be asked to provide stool samples at baseline and 4-weeks post iron therapy to assess any microbiome changes in response to iron therapy.

Inclusion Criteria:

1. Written informed consent before participating in the study after being given a full description of the study and prior to any study-specific procedures being performed.
2. Male or non-pregnant female and is age 18 years to 80 years.
3. Can communicate well with the Investigator and to comply with the requirements for the entire study.
4. Capacity to understand written English.
5. New diagnosis iron-deficient anaemia.
6. Prescribed IV iron therapy or oral iron supplementation which contains 65mg elemental iron, two or three times per day for a period of at least 1 month or, will receive 1000mg or 1500mg of intravenous iron, as part of their standard care.
7. Participant agrees to wait until after taking baseline breath samples and completing the IBS-SSS questionnaire before starting their iron therapy.
8. Participant agrees to follow pre-test diet for 24 hours before giving test sample.
9. Participant agrees to refrain from strenuous physical activity on the day of the breath test.
10. Refrain from smoking on the day of the breath test.
11. Agree to complete an overnight fast on the night before the breath test. Food and drink must be withheld until after all breath test samples have been taken.
12. No probiotics for 14 days before the breath test or during the study.
13. Body mass index between 18.5 and 34.9kg/m2 (bounds included).
14. Not antibiotics for 4-weeks before the start of the study or during the study

Exclusion Criteria:

1. Using an opioid based medication.
2. Antibiotics in the 4 weeks prior to enrolment.
3. Colonoscopy/sigmoidoscopy in the 1 week prior to enrolment, unless they have taken their baseline breath sample and IBS-SSS questionnaire before completing the required bowel preparation.
4. Diagnosis of any organic gastrointestinal disease, including inflammatory bowel disease, coeliac disease and diverticulitis.
5. Mechanical obstruction of the GI tract.
6. Participant is diabetic.
7. Participant has any hepatic disease.
8. Participant has any disease of the CNS.
9. Participant is involved in this study as an Investigator, sub-Investigator, study coordinator, other study staff, or sponsor member.
10. Previous abdominal or colorectal surgery except appendectomy, cholecystectomy, or hysterectomy.
11. Participant has had iron therapy in the 12 months prior to enrollment.

100 oral iron participants 55 IV iron participants