AIM: Dose regimens of methotrexate used in the medical treatment of ectopic pregnancy vary. In this study, factors determining single- dose and additional-dose methotrexate regimens were investigated. MATERIAL AND METHOD: Patients diagnosed with ectopic pregnancy between 1 January 2012 and 31 August 2022 at a tertiary care center were reviewed, retrospectively (n=383). Those lost to follow- up (n=36) and those who underwent surgery (n=186) were excluded. Medical characteristics, ultrasonography findings, and laboratory values of patients treated with single-dose methotrexate (n=128) and patients treated with additional doses (n=30) were compared. p<0.05 was considered significant. RESULTS: There was no significant difference between the patient characteristics and medical history. The need for additional dose was less in patients with more pelvic fluid on ultrasonography (p<0.001). Patients with a day 4/day 1 β-hCG ratio of 0,8474 and above required an additional dose of methotrexate (p<0.001). CONCLUSION: Different parameters have been defined for patient selection for effective medical treatment of ectopic pregnancy. In this study, the effects of ultrasonography findings and β-hCG levels at follow-up on patient selection were quantitatively determined. The combination of day 4/day 1 β-hCG ratio and ultrasonography findings may help to identify patients in need of additional doses of methotrexate.