Comparison 11. Iron supplementation versus placebo/control: low risk of performance bias.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Deferral due to low haemoglobin (primary outcome)	3		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
1.1 Deferral at first donation visit after commencement of treatment	3	833	Risk Ratio (M‐H, Random, 95% CI)	0.29 [0.17, 0.50]
1.2 Deferral after multiple donation visits	2	541	Risk Ratio (M‐H, Random, 95% CI)	0.22 [0.11, 0.42]
1.3 Cumulative deferrals over multiple donation visits	3	1820	Risk Ratio (M‐H, Random, 95% CI)	0.25 [0.18, 0.35]
2 Haemoglobin (g/L)	3		Mean Difference (IV, Random, 95% CI)	Subtotals only
2.1 Before further donation	3	270	Mean Difference (IV, Random, 95% CI)	4.76 [1.07, 8.45]
3 Serum ferritin (ng/mL)	3		Mean Difference (IV, Random, 95% CI)	Subtotals only
3.1 Before further donation	3	594	Mean Difference (IV, Random, 95% CI)	13.31 [7.22, 19.40]