Competing in weight sensitive sports increases the risk for low energy availability (EA) which is associated with health impairments. Most of the available evidence on syndromes that result from low energy availability is in female athletes. PURPOSE: To identify body composition, caloric intake, physical activity, and other risk factors for developing the syndrome of Relative Energy Deficiency in Sport (RED-S) in female runners. METHODS: 31 female recreational runners completed a sociodemographic and an adaptation to the RED-S CAT tool to evaluate 12 risks factors for RED-S, a 7-day weekly exercise record based on calories spent on training sessions using their heart rate monitor, a 3-day dietary record (two work days and one weekend day) completed with the app “My Fitness Pal” and a body composition evaluation by bioimpedance. Energy availability was calculated and classified as: No risk (≥45 kcal/kg LBM/day); Moderate risk (30-45 kcal/kg LBM/day); and At risk (≤30 kcal/kg LBM/day). RESULTS: Age of 33±6.0 years with experience of 7 to 9 years. The average personal record in 10 kilometers was 40:24:48±2.0 minutes. The average body mass was 53±5.3 kg, BMI=20.9±1.6 kg/m², a percentage of body fat=26.4±3.7% and lean body mass=38.9±3.1 kg. The average reported daily exercise caloric expenditure was 529.5±176.4 kcal and daily caloric intake was 1679.5±327.7 kcal. Results showed an EA of 1147.7±343.3 kcal/day, or 29.6±9.1 kcal/kg of LBM/day. Only 6% of the runners were classified as no risk, 42% as moderate risk and 52% as at risk. Other risk factors were history of interrupted menstrual cycles (42%), birth control pills (29%), non-nutritional technique to lose weight (22%), history of eating disorder (16%), stress fracture (10%), hormonal disorder (7%). There was a weak and non-significant correlation between EA and personal best (r=0.45, p=0.811) CONCLUSION: This group of Costa Rican runners demonstrate energy availability that is far below from the optimal and various risk factors to develop the syndrome of Relative Energy Deficiency in Sport.