Oral iron absorption test should not be performed with iron drops containing ferric iron.

Introduction: In an oral iron absorption test (OIAT), the rise in plasma iron concentration after oral ingestion of iron is a measure of intestinal iron absorption. We describe results of the OIAT using two different formulations of oral iron drops.
Methods: The study included all patients who had an OIAT performed at the Department of Internal Medicine, Farsø, Aalborg University Hospital, Denmark, from 1 January 2013 to 17 June 2014 (n = 24) using ferrous iron drops "Glycifer" and from 18 June to 3 November 2014 (n = 17) using ferric iron drops "Medic". A venous blood sample was drawn before and then 90, 180 and 240 min. after the intake of 9 ml iron drops of the "Glycifer" brand (270 mg ferrous iron) or the intake of 11 ml iron drops of the "Medic" brand (264 mg ferric iron).
Results: The patient characteristics (ferrous versus ferric iron drops) were similar in terms of gender, age, haemoglobin, ferritin and previous gastric bypass surgery. The fasting baseline plasma iron concentration was median 5 μmol/l in both groups (p = 0.4). The maximum plasma iron concen-tration increase from baseline after oral intake of the iron drops was median 2 μmol/l (range: 0-8 μmol/l) in the group given ferric iron drops and 48 μmol/l (range: 14-78 μmol/l) when ferrous iron drops were used (p < 0.001).
Conclusion: OIAT performed with ferrous or ferric iron drops showed very different results with a lack of plasma iron concentration increase after ingestion of ferric iron drops.
Funding: none.
Trial Registration: not relevant.