ABSTRACT Background Aim Methods Results Conclusion Relevance to Clinical Practice Reporting Method Diabetes is a global problem. Diabetes nurses, in particular, take great responsibility in reducing and controlling the fears of individuals using insulin and increasing their capacity to tolerate discomfort.This study was conducted to examine the effects of the capacity to tolerate discomfort on the fear of self‐injection and the status of testing blood glucose levels in patients with type 1 and type 2 diabetes using insulin.This cross‐sectional study was conducted between December 2022 and February 2023 with 320 adult patients with type 1 and type 2 diabetes using insulin who were followed up in the Endocrinology and Internal Medicine Clinics of a university hospital in Turkey. The data analysis process included analyses of the frequency, independent‐samples t‐tests, one‐way ANOVA, the Kruskal–Wallis H test, and Pearson's correlation analysis. Data were analysed using the IBM SPSS v27.0 software, considering alpha as 0.05.The mean total Discomfort Intolerance Scale score of the patients was 22.78 ± 6.74, and the mean Fear of Self‐Injecting and self‐testing was 21.1 ± 6.7. A negative significant correlation was found between the discomfort intolerance levels of the patients and their levels of fear of self‐injection and self‐testing (p < 0.05).Individuals with a higher capacity to tolerate discomfort have lower levels of fear of self‐testing and self‐injection. Therefore, the fear of self‐testing and self‐injection in patients using insulin injections may affect diabetes self‐management.Individuals with low tolerance for discomfort should be identified, interventions to increase tolerance in individuals at risk should be planned, and diabetes self‐management should be better supported.The reporting of the results of the study adhered to the STROBE guidelines. [ABSTRACT FROM AUTHOR]