Birgegard 2010.

Methods	Type of study: parallel, 2‐arm randomised controlled trial Country of study: Sweden Study setting: single blood donation unit Number of participants randomised: Treatment arm 1: 60 Treatment arm 2: 60 Number of participants analysed (at 12 months): Treatment arm 1: 57 Treatment arm 2: 55  Follow‐up time points: 3 (female) or 4 (male) donations subsequent to baseline donation. Final donation is at least 1 year after first donation Hb threshold for deferral from donation: not reported Source of funding: supported by an unrestricted grant from Renapharma AB
Participants	Regular donors with at least 5 previous donations within the past 1 to 2 years Mean age (years): Treatment arm 1: 50.3 (SD 8.0) years Treatment arm 2: 50.3 (SD 8.0) years Sex (male/female): 41.7%/58.3%
Interventions	Treatment arm 1: oral iron (Fe2+) sulphate corresponding to Fe2+ 100 mg (Duraferon): one 100 mg tablet taken daily for 20 days after each blood donation. Total dose: 200 mg after each donation Treatment arm 2: intravenous iron (III) sucrose (Venofer); 200 mg (10 mL of 20 mg/mL iron (III) as iron sucrose, corresponding to 200 mg iron (III), given after each blood donation. Total dose: 200 mg after each donation
Outcomes	Iron status at end of study (primary outcome); iron status at other time points as well as in men versus women and younger versus older women; RLS frequency and severity
Notes	This study performed intention‐to‐treat analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Central randomisation was performed via a web‐based system using the minimisation method to ensure baseline balance for age and blood B‐Hb"
Allocation concealment (selection bias)	Unclear risk	"Central randomisation was performed via a web‐based system using the minimisation method to ensure baseline balance for age and blood B‐Hb"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Study participants were not blinded
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 (3/60 versus 5/60 after 12 months) 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	Low risk	"The study was supported by an unrestricted grant from Renapharma AB"