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

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.

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).

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).

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.

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