Purpose The aim of the study was to investigate the association between serum 25-hydroxyvitamin D status within the last 6 months prior to COVID-19 infection and parameters of immune function and clinical outcomes. Methods Fifty-six patients, who were admitted to the emergency clinic and diagnosed with COVID–19 infection, were included in the study. Data on clinical characteristics, inflammatory parameters and vitamin D status were recorded for each patient. All the participants had data on 25-hydroxyvitamin D status within the last 6 months prior to COVID-19 infection. Results The patients were stratified as those with vitamin D status less than 20 ng/mL and higher than 20 ng/mL. A group with vitamin D status less than 20 ng/mL had lower lymphocyte counts and lower haemoglobin levels that was statistically significant (respectively; p = 0.021, p = 0.035). Higher C-reactive protein (CRP) levels were seen in the vitamin D–deficient group ( p = 0.013). It was observed that vitamin D status of the patients who required oxygen therapy were lower than those who did not require oxygen therapy, not statistically significant ( p = 0.05). Patients who did not use vitamin D supplementation within 6 months prior to COVID-19 infection had more likely to be diagnosed with pneumonia ( p = 0.004). Conclusion Cases with lower vitamin D status had increased inflammatory markers and worse clinical outcomes than patients with higher vitamin D status. This study suggests that vitamin D status can be used as a prognostic factor in COVID-19 patients, and vitamin D supplementation can be recommended to improve the clinical outcomes in COVID-19 infection.

In our study, the greater frequency of restless legs syndrome, depressive symptoms, and fibromyalgia in the patients with migraine supports the role of dopamine, which is common to all three disorders. Interviews focused on these problems among migraine patients may help to decide on the best available treatment modality.