Aim:Carpal tunnel syndrome (CTS) is the most common peripheral entrapment neuropathy. Several factors were associated with CTS prevalence, such as body mass index (BMI), diabetes mellitus (DM), hypothyroidism, and occupational factors. However, few studies have investigated the factors that affect the severity of CTS. Moreover, patients with more severe diseases were more inclined toward surgery, suggesting that disease severity affects patient behavior. This study evaluated the effects of factors, which are associated with CTS prevalence, on disease severity.Material and Methods:This retrospective study included 206 patients who were treated surgically for either moderate or severe CTS. Patients were grouped into moderate and severe CTS groups and then compared regarding age, gender, BMI, and presence of occupational factors and systemic diseases that are associated with CTS.Results:Patients with moderate and severe CTS did not differ in age, gender, occupational risk factors, and most of the systemic diseases, including DM, hypothyroidism, rheumatoid arthritis, cardiovascular disease, renal insufficiency, and folate deficiency. The severe CTS group had a significantly higher BMI than the moderate CTS group. Moreover, vitamin B12 deficiency was significantly more common in the severe CTS group than in the moderate CTS group.Conclusion:Patients with severe CTS are more inclined toward surgery than those with moderate CTS. Controlling BMI and preventing vitamin B12 deficiency may help keep alleviate complaints related to CTS with less invasive treatment modalities.