Effect of Vitamin C on Blood Glucose Levels, Glycosylated Hemoglobin, and Serum Lipid Profile in Patients With Type 2 Diabetes Mellitus: A Systematic Review

Abstract

Background Type 2 Diabetes Mellitus (T2DM) is a metabolic disorder characterized by insulin resistance and chronic hyperglycemia, often complicated by dyslipidaemia. Oxidative stress plays a crucial role in the pathogenesis and progression of T2DM. Vitamin C has been proposed as a beneficial adjunct to conventional therapy due to its potential effects on glycemic control and lipid metabolism. Methodology Databases including PubMed, Scopus (Q2), and Web of Science were searched up to June 2025. Studies were included if they evaluated the effects of oral Vitamin C supplementation in adults with T2DM and reported outcomes on blood glucose, HbA1c, or lipid parameters. A total of 15 RCTs were included after screening 446 records. Results and Discussion Vitamin C supplementation, particularly at doses ≥500 mg/day and for durations ≥6 weeks, was associated with a significant reduction in fasting blood glucose and HbA1c in most trials. Some studies reported favourable changes in lipid parameters, such as reductions in triglycerides and LDL cholesterol, and an increase in HDL cholesterol. Conclusion Vitamin C appears to offer beneficial effects on glycemic control and lipid profile in individuals with T2DM, particularly when administered in adequate doses and durations.