Purpose The aim of this review was to integrate empirical and theoretical literature on fatigue among adults with type 1 diabetes mellitus (T1DM). A methodological review using an integrative approach was used. Databases MEDLINE via Pubmed, CINAHL, PsycINFO, and Science Direct were searched for peer-reviewed articles published in English from 2007-2017, using the following search terms and Boolean operators: "Type 1 Diabetes" and "Fatigue." Of 199 articles initially retrieved, 14 were chosen for inclusion. These articles included 13 quantitative (7 cross-sectional, 2 cohort, 2 secondary data analyses, 2 experimental) and 1 qualitative phenomenology. Fatigue was identified as one of the most troublesome symptoms reported in persons with T1DM. Four main themes emerged: fatigue in T1DM is multidimensional and related to psychological, physiological, situational, and sociodemographic factors. Conclusions Fatigue is considered a classic symptom of hyperglycemia; however, there were minimal data to support the theory that fatigue is related to hyperglycemia or hypoglycemia. Studies on fatigue among persons with T1DM are limited to small samples and cross-sectional designs with few randomized controlled trials addressing fatigue and diabetes-related symptoms. Evidence is conflicting regarding the onset of fatigue among persons with T1DM and the relationship between fatigue and diabetes duration. The prevalence of fatigue is likely influenced by disease physiology, psychological stress, and lifestyle factors, but more research is needed to confirm these relationships as causal inference is unclear.