Diabetes mellitus (DM) is the leading cause of non-traumatic lower extremity amputations in the USA. After these amputations, patients exhibit reduced mobility and increased energy demands of walking. The best surgical practice is to preserve as much of a functional limb as possible, in part due to the fact that proximal amputations result in a greater increase in energy expenditure compared to more distal amputations. While differences in transfemoral, transtibial and partial foot amputation levels have been previously documented, no studies have directly compared transtibial and transmetatarsal amputees. The present study aimed to compare energy expenditure and patient-reported outcomes in patients with diabetes mellitus who have undergone transmetatrsal (TMA) and transtibial amputations (TTA). Thirty-nine DM participants with either unilateral TMA, unilateral TTA or no amputations (control group) participated in this observational study. Energy expenditure, heart rate (HR) and distance travelled during six-minute walk test (6MWT), the Foot and Ankle Ability Measure (FAAM) and the Patient-Reported Outcomes Measurement Information System (PROMIS-29) were measured at a single research visit. No significant differences between the three groups were detected in energy expenditure, HR or distance covered during 6MWT, as well as in PROMIS-29 or FAAM patient-reported outcomes. While the results of this study suggest no differences in functional and patient-reported outcomes between transmetatarsal and transtibial amputees, a larger sample size that would allow for control of comorbidities is needed.