Magnesium is the second most common cation in the cell. In addition to its role as a cofactor in many enzymatic pathways in physiological processes, it is necessary for the regular functioning of vascular smooth muscle cells. Magnesium deficiency has been associated with exacerbation of inflammation, which plays a role in the aetiopathogenesis of many diseases. To investigate the potential relationship between serum magnesium level and the development of chronic venous insufficiency by comparison with healthy individuals. The study included 394 patients with venous insufficiency based on physical examination findings and colour Doppler ultrasonography, and 206 controls without venous insufficiency. Venous insufficiency was defined by colour Doppler as reflux lasting 0.5 seconds or more in superficial veins, and longer than one second in femoral and popliteal veins. Clinical, haematological and biochemical parameters, including serum magnesium level and indicators of inflammation, were compared between groups. A total of 600 participants were included. There was no significant difference between the groups in terms of age and gender. In total, 187 (47.46%) patients with chronic venous insufficiency and 105 (50.97%) of the control group were male (p=0.414). The median age of the patients with chronic venous insufficiency was 48 (min-max: 41-49), and the median age of the control group was 49.00 (min-max: 45.00-60.25) (p=0.064). Serum magnesium level was found to be significantly lower in the group with chronic venous insufficiency compared to the control group; 1.90 mg/dL (min-max: 1.82-2) versus 2.1 mg/dL (min-max: 2-2.2) (p<0.001), respectively. Low serum magnesium levels may pose a potential risk for the development of chronic venous insufficiency, which is common in the community.