Introduction: Vitamin D is well known as immunmodulator leads to significant reduction in inflammatory markers in COVID 19 patients. Additional, recovery time of cough and gustatory sensory is reduced within supplementation of vitamin D. The term post-COVID-19 condition (PCS) describe new, returning or ongoing symptoms more than 12 weeks after COVID-19 infection which cannot be explained by other disorders. The role of vitamin D level in PCS patients is not clear.
Methods:  We conducted a retrospective analysis of vitamin D level in a PCS cohort. Taking of a blood sample was part of the routinely assessment in PCS consultation hours. The values were compared with a historic health group in the previous years.
Results: Compared to patients without a SARS-CoV2-infection in the year 2019-2021 we found a significant decrease in vitamin D level in the post-COVID group (PCS 2021: 17,4ng/ml/2019: 23,5ng/ml/2020: 21,9ng/ml/2021: 21,2ng/ml).
Discussion: The decrease in vitamin D level in a PCS cohort could have several reasons. First, an acute SARS-CoV2 infection can lead to a specific consumption. Second, the reduced activity in symptomatic PCS patients could reduce the level. Third, reduced vitamin D are the expression of a ongoing (immunological-driven) PCS pathology. Whether, decreased vitamin D level can trigger PCS symptoms must be clarified in a prospective study.