The “expanded MUAC-only” approach is being used in acute malnutrition programming, with a mid-upper arm circumference (MUAC) of <125mm as the only measurement for screening and admission for treatment. This study explored the impact of the approach on eligibility for treatment and access to ready-to-use therapeutic foods. The results showed that 25 percent of all severe acute malnutrition cases would be undiagnosable with this measure; a further 20 percent would be misreported as moderate acute malnutrition.