Vitamin K consumption needs to be monitored in people taking warfarin since it can impact the anticoagulation response. Vegetables are the primary nutritional source of Vitamin K1, in the form of Vitamin K1. The aim of this study was to measure the level of Vitamin K1 in various vegetables that were commercially sold in three major Bandung markets and were ingested by patients using warfarin at Hasan Sadikin Central General Hospital Bandung. High-performance liquid chromatography with an ultraviolet detector set at 245 nm was the analytical technique. One hundred percent methanol was used as the mobile phase, and it was isocratically eluted at a flow rate of 0.6 mL/min with a T3 column maintained at 25°C. The results indicated that the following Vitamin K1 levels were found in lettuce: 38.4391 ± 15.2650–64.4419 ± 19.0315 µg/100 g, in napa cabbage: 56.7445 ± 0.1569–273.2828 ± 8.3061 µg/100 g, in cabbage: 27.9531 ± 1.7487–217.0457 ± 7.2201 µg/100 g, and in spinach: 305.2868 ± 3.3058–970.7098 ± 14.1167 µg/100 g. The highest Vitamin K1 level was in spinach and the lowest was in lettuce.