A placebo will be produced, consisting of the same ethanol solution as Vi-De 3® Monthly Dose, but without cholecalciferol.

Assessed by the Fatigue Severity Scale (FSS) questionnaire, using a 8-step scale (1-7) with total range 9-63 and higher scores indicating worse outcomes.

The occurrence of pain since the last visit is assessed by one question of the SCI Secondary Conditions Scale (Kalpakjian, Scelza et al. 2007), providing a five-step rating (0-4) with a higher score indicating a worse outcome.

The occurrence, kind, location and interference of pain during the last week is assessed using questions of the adapted version of the International SCI Pain Basic Data Set (Widerström-Noga, Biering-Sørensen et al. 2008). The interference of pain is measured on a 11-step scale (0-10), with total range 0-30 and higher scores indicating worse outcomes.

The occurrence, localization and severity of pressure injuries is assessed by the exact questions of the first-wave questionnaire of the Swiss Spinal Cord Injury Cohort Study (SwiSCI) survey (Post, Brinkhof et al. 2011, Brinkhof, Fekete et al. 2016). The severity or grade is assessed using the European and US National Pressure Ulcer Advisory panels' (EPUAP-NPUAP) classification (National Pressure Ulcer Advisory Panel and Alliance. 2014), using a 4 point scale (1-4) and higher grades indicating worse outcomes.

Functional independence during daily living will be assessed by the Spinal Cord Independence Measure (SCIM, 3rd version)

Serum levels of calcium (mmol/L) to monitor hypercalcemia

Serum levels of parathyroid hormone (ng/L) will be monitored as it is correlated to vitamin vitamin D status

Serum levels of phosphate (mmol/L) will be monitored as it is correlated to vitamin D status

Serum levels of cystatin C (mg/L) to monitor kidney function

Serum levels of estimated glomerular filtration rate (eGFR) (mL/min) to monitor kidney function

Serum levels of testosterone (ng/dL) will be monitored as it is correlated to vitamin vitamin D status

The occurrence of urinary tract infections since the last visit is assessed by the exact questions of the first-wave questionnaire of the Swiss Spinal Cord Injury Cohort Study (SwiSCI) survey (Post, Brinkhof et al. 2011, Brinkhof, Fekete et al. 2016).

The time spent outdoors (min) with level of exposed skin during the last 7 days, following Hanwell et al (2010).

Six categories ranging from light to very dark skin types based on Fitzpatrick (1975)

Time since SCI (years), neurological level of injury (NLI), and the degree of impairment following the American Spinal Injury Association (ASIA) Impairment Scale (AIS)

Physical activity (hours and number of trainings), medication and nutritional supplements, and illnesses will be assessed by questionnaire. Weight will be measured on a scale.