Vitamin D deficiency was associated with longer hospital stays (p = 0.04), longer ICU stays (p = 0.04), more days of invasive mechanical ventilation (IMV) (p = 0.04), lower skeletal muscle mass/weight (SMM/w) (p = 0.04) and skeletal muscle index (SMI) (p = 0.047), higher fat mass percentage (FM%) (p = 0.04), C-reactive-protein (CRP) (p = 0.04), and glycated hemoglobin (HbA1c) (p = 0.03), and better performance in R-HGS (p = 0.04), UAG (p = 0.03), and 6MWT (p = 0.034) when compared with those with normal vitamin D levels. Here, CRP is linked to vitamin D deficiency.