Background: Physical training by female military trainees can put them at risk of iron deficiency and inferior health and performance.

Purpose: To determine the effect of iron supplementation on iron status, fitness, fatigue, and leisure activities.

Material and Methods: In this randomised, double-blind, placebo-controlled trial, female officers-in-training were randomly allocated to treatment (n = 25, 18 mg iron) or placebo tablets (n = 24). Outcomes were iron status, fitness, fatigue, and leisure activity at baseline, seven weeks and 13 weeks.

Results: Ferritin declined by midpoint in the placebo group (P = 0.001). There was a treatment effect in the second half of the trial in emotional fatigue (-4.2 to -0.6 95% CI, P = 0.04). There was a negative relationship with iron intake for emotional fatigue (OR 0.61; 0.44 to 0.87 95% CI; P = 0.006) and positive for vigour (OR 1.51; 1.08 to 2.11 95%CI; P = 0.016) and small negative association between initial dietary iron intake and initial serum ferritin (0.2 to 9.2 μg/L 95% CI; P = 0.042). Conclusion: Officer training affects iron status and iron supplementation improves indicators of iron status and emotional fatigue in female officers-in-training.