Gordeuk 1987a.

Methods	Type of study: parallel, 3‐arm randomised controlled trial Country of study: USA Study setting: multi‐centre: 3 fixed site collection facilities Number of participants randomised: Treatment arm 1: 24 Treatment arm 2: 26 Treatment arm 3: 25 Number of participants analysed: Treatment arm 1: 15 Treatment arm 2: 17 Treatment arm 3: 19 Follow‐up time points: day 56 after baseline donation Hb threshold for deferral from donation: not reported (Hct 38%) Source of funding: sponsored in part by Food and Drug Administration Orphan Drugs Development Grant
Participants	Female donors of child‐bearing age with Hct ≥ 38% who had donated blood at least once previously Mean age (years): not reported Sex (male/female): 0%/100%
Interventions	Treatment arm 1: oral carbonyl iron, 600 mg taken 3 times daily for 7 days. Total dose: 12,600 mg Treatment arm 2: oral ferrous sulphate, 300 mg (60 mg Fe2+) taken 3 times daily for 7 days. Total dose: 1260 mg Fe2+ Treatment arm 3: oral placebo, taken 3 times daily for 7 days
Outcomes	Haemoglobin; mean corpuscular volume; free erythrocyte protoporphyrin; serum ferritin; serum iron; total iron binding capacity; transferrin saturation; adverse effects
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of randomisation was not reported
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Blinding of study participants was not reported although the study was described as "double‐blind" and identical capsules were used for both treatment and placebo
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding of outcome assessors was not reported
Incomplete outcome data (attrition bias) All outcomes	High risk	The number of withdrawals differed between treatment arms (9/26 versus 6/25)
Selective reporting (reporting bias)	Unclear risk	All outcomes listed in the manuscript were reported, but no study protocol was available to determine the full list of pre‐specified outcomes
Other bias	Low risk	No other sources of bias identified