Abstract BACKGROUND: Reports depicted insufficient plasma Vitamin C levels and significant associations to both acute and chronic inflammation. Recently, use of intravenous Vitamin C has gained visibility for its effectiveness in coronavirus-19 treatment. There were no studies available currently to detect the clinical correlation between plasma Vitamin C with risk factors of coronary artery disease (CAD). The present aim of the study is to estimate the Vitamin C levels in CAD patients as well as to correlate with clinical and laboratory variables to assess the severity of CAD and also to formulate a diagnostic strategy. METHODS: A prospective comparative study was conducted in 100 diagnosed cases of CAD and estimate plasma Vitamin C levels and compared with healthy individuals. Spearman correlation analysis was performed between Vitamin C levels and risk factors of CAD. RESULTS: Maximum CAD cases were in the age group of 60–70 years. The mean age was 58.54 ± 11.60 years in the CAD patients. Among risk factors, 54% of patients had hypertension, 54% of patients had diabetes mellitus, and 27% of patients had dyslipidemia. There significant association noted between diabetes and type of CAD (P = 0.015). Among CAD cases, 70% of patients had ST-elevation myocardial infarction (STEMI), 11% of patients had a non-ST-elevation myocardial infarction (NSTEMI), 17% of patients had unstable angina (USA), and only 2% of patients had central sleep apnoea (CSA). Angiogram diagnosis shows that 34% of patients had single-vessel disease (SVD), 28% of patients had double-vessel disease (DVD), 8% of patients had triple-vessel disease (TVD), 2% of patients had left main coronary artery (LMCA) disease, 13% patients had mild CAD, and 15% patients had normal epicardial coronaries. The range of plasma Vitamin C concentrations level was from 33.25 to 92.5 μmol/L in CAD patients. The mean plasma Vitamin C concentration levels in CAD patients were lower than in healthy individuals (66.96 ± 13.6 vs. 71.33 ± 10.8 μmol/L). There was no statistically significant difference between CAD and non-CAD for plasma Vitamin C concentration levels (P = 0.085). The mean Vitamin C level was higher in DVD (70.6 ± 10.9) than the TVD, LM (71.6 ± 5.82), SVD (68.49 ± 12.4), mild CAD (65.55 ± 13.1), and TVD (62.92 ± 8.9). There was no statistically significant difference in plasma Vitamin C levels in the coronary angiogram (CAG) diagnosis for CAD cases (P = 0.103). The mean plasma Vitamin C levels were higher in NSTEMI (72.98 ± 10.8) than the STEMI (69.5 ± 12.5), USA (63.6 ± 15.2), and CSA (58.45 ± 3.5) μmol/L. There was no statistically significant difference in plasma Vitamin C levels in the type of CAD (P = 0.135). A negative correlation is noted between Vitamin C and low-density lipoprotein (LDL) cholesterol (r = −0.32, P = 0.02). Similarly, there is a negative correlation between Vitamin C and TGL (r = −0.28, P = 0.0067), whereas there is a positive correlation between Vitamin C and high-density lipoprotein (HDL) (r = 0.27, P = 0.0025). CONCLUSION: The mean of Vitamin C concentration levels was lower in CAD patients than in healthy individuals. There is a significant negative correlation between Vitamin C and LDL and between Vitamin-C and TGL. A positive correlation was observed between Vitamin-C and HDL. Vitamin C along with HDL was markedly decreased in CAD and may be the cause. Hence, the combination of Vitamin C, LDL, and HDL can be considered prognostic detectors to know the CAD at its early stages.