This review aimed to identify the most effective treatment for iron deficiency in women in developed countries and children in developing countries with consideration of side effects, adherence and sustainability. Studies were excluded if they involved: disease states affecting iron status; pregnant, lactating or postpartum women; groups of participants with mean haemoglobin and/or serum ferritin above deficient cut-offs at baseline; articles published prior to 1980; studies of animals and studies not written in English. All included articles were assessed for quality using the 2008 American Dietetic Association Quality Criteria Checklist. Most articles were of a high quality with nine being scored positively and five scoring a neutral result. Fourteen randomised trials were found, with two studies on adult women in developed countries and twelve studies on children in developing countries. Iron supplementation was the most effective and timely solution; however, side effects were common. A 30-60 mg daily dose of elemental iron may correct iron deficiency anaemia within 8 weeks. Dietary strategies and fortification showed promising results over a longer time period. Limitations of research included: nutritional and disease confounders such as multiple nutrient deficiencies and parasitic infection; lack of international uniformity of haematological definition of iron deficiencies; side effects of iron therapy affecting adherence to treatments; and treatment effectiveness being dependent on individual variations in iron absorption depending on stage of iron depletion and duration of study. Further longer-term research and research on supplement and fortificant formulation is required.