Introduction and aim. Following the use of repurposing drugs to successfully manage coronavirus disease 2019 (COVID-19) patients in an Infectious Diseases Center (IDC) in Nigeria, it was imperative to assess haematological changes and metabolic alterations in these patients which may inform recommendations for future use. Material and methods. Blood samples of admitted COVID-19 Nigerian patients during therapeutic management were analysed for haematological- (total white blood cells (WBC), lymphocyte, monocyte, neutrophil, eosinophil, basophil and neutrophil: lymphocyte ratio) and blood chemistry- parameters [total protein, total and conjugated bilirubin, alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine transaminase (ALT), gamma-glutamyl transferase (GGT), albumin, urea, creatinine, total cholesterol, triglycerides, low-density lipoprotein (LDL), high-density lipoprotein (HDL), PO4 3-, Ca2+, uric acid, Na+, K+, Cl- and HCO3 -] using autoanalysers. The percentages of patients having values below, within and above reference ranges were compared using Chi-square test while the mean values at admission were compared with mean values at discharge using Student t-test. Results. The mean values of total protein, albumin, Na+, HCO3 -, uric acid, Ca2+, WBC, platelets, lymphocytes, eosinophils and basophils were significantly increased in COVID-19 patients at discharge compared with COVID-19 patients at admission. Also, more percentages of COVID-19 patients at discharge compared with COVID-19 patients at admission had albumin, ALP, total bilirubin, HDL, Na+, K+, Cl-, HCO3 -, urea, creatinine, WBC, lymphocytes, neutrophils, monocytes, eosinophils and basophils within normal reference intervals. Conclusion. This study showed that most metabolic and haematological derangements were normalised by repurposing drugs in most of the COVID-19 patients at this IDC, thus supporting the continuous use of this therapeutic option.