Radtke 2004b.

Methods	Type of study: cross‐over, 2‐arm randomised controlled trial Country of study: Germany Study setting: not reported Number of participants randomised: Treatment arm 1: 131 Treatment arm 2: 129 Number of participants analysed (at visit 3): Treatment arm 1: 108 Treatment arm 2: 103 Follow‐up time points: 3 donation visits subsequent to baseline donation; inter‐donation interval 8 to 10 weeks Hb threshold for deferral from donation: 145 g/L (before first donation); 140 g/L (before subsequent donations) Source of funding: supported in part by a grant from Sanol/Schwarz Pharma, Monheim, Germany
Participants	Regular donors with minimum body weight 68 kg; meeting the Hb threshold Mean age (years): not reported; all groups combined: range 18 to 62 Sex (male/female): 98.8%/1.2%
Interventions	Treatment arm 1: oral iron (iron(II)‐glycine‐sulphate‐complex (Sanol/Schwartz Pharma, Monheim, Germany), 100 mg Fe2+ taken daily between baseline and 3 subsequent visits (between 56 and 70 days). Total dose: 16,800 mg to 21,000 mg Treatment arm 2: oral placebo (Sanol/Schwartz Pharma, Monheim, Germany); taken daily between baseline and 3 subsequent visits (between 56 and 70 days)
Outcomes	Donations and deferrals; haemoglobin; serum ferritin; adverse effects; compliance
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Patients were assigned to treatment by "block randomization with variable block length"
Allocation concealment (selection bias)	Unclear risk	Patients were assigned to treatment by "block randomization with variable block length"
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"
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding of outcome assessors was not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	The number of randomised participants with missing data was similar in each group (23/131 versus 26/129 at the third visit) with less than 5% difference in attrition rate between treatment arms
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	High risk	The study was supported in part by a grant from Phyt‐Immun GmbH, Homburg, Germany