OBJECTIVE: Mepolizumab, an anti-IL-5 monoclonal antibody, has shown promise in reducing exacerbations and steroid dependency in severe eosinophilic asthma. This study aims to evaluate the effectiveness of mepolizumab in achieving clinical remission in asthma over 12 months and explore Vitamin D levels as a predictor of response. METHOD: We assessed Asthma Control Questionnaire (ACQ) scores, spirometry, number of exacerbations, oral corticosteroid (OCS) use, and inhaled corticosteroid (ICS) use in 32 patients, observing significant clinical improvements. Data were collected 1 year prior to starting mepolizumab and one year after starting mepolizumab. Nasal polyps were not seen in all the patients, and computed tomography of para-nasal sinuses are not available for all the patients, so nasal polyps status are not evaluated to avoid any bias. RESULT: Our results indicate that 12 patients achieved clinical remission after starting mepolizumab, with a strong correlation between higher Vitamin D levels and positive treatment outcomes. This suggests that optimizing Vitamin D levels could enhance the response to mepolizumab in asthma patients, and help in achieving better asthma control. CONCLUSION: Mepolizumab is an effective treatment for severe eosinophilic asthma, significantly improving clinical outcomes and reducing corticosteroid use. This study highlights the importance of Vitamin D as a predictor of response to mepolizumab, suggesting that higher Vitamin D levels may enhance treatment efficacy.