Objective This study aims to investigate the levels of various serum vitamins in patients with digestive system tumors analyze the differences in vitamin deficiencies among different categories of tumor patients and further explore the correlation between serum vitamin levels protein indicators and inflammation indicators. This research aims to provide a scientific basis for vitamin supplementation in clinical patients with digestive system tumors. Methods We collected the results of serum vitamin tests for 13 463 in-patients with digestive system tumors in Changhai Hospital from January 2018 to June 2023. Statistical software SPSS 21. 0 was used for variance analysis to compare serum vitamin levels and chi-square tests were conducted to analyze the differences in deficiency rates of various vitamins in different types of digestive system tumors. Additionally Spearman correlation analysis was employed to investigate the correlation between serum vitamins and protein and inflammation indicators Results Digestive system tumor patients significantly lack water-soluble vitamins vitamin B1 vitamin C and vitamin B6 with an overall deficiency rate of 67. 75% 61. 51% and 32. 17% respectively. The significant deficiency of fat-soluble vitamin vitamin D is observed with an overall deficiency rate of 63. 60%. The deficiency rates of vitamin B1 in esophageal cancer gastric cancer colorectal cancer and pancreatic cancer are significantly higher than those in liver cancer patients 69. 11% 69. 03% 72. 62% 74. 14% vs. 18. 41% P < 0. 001 . The serum folate deficiency rate in liver cancer patients is much higher than in the above four types of digestive system tumor patients 46. 44% vs. 9. 02% 13. 13% 12. 82% 5. 70% P < 0. 001 . Spearman correlation analysis demonstrates that the levels of serum vitamin C and vitamin B6 in digestive system tumor patients are positively correlated with serum albumin vitamin C r = 0. 207 P < 0. 001 vitamin B6 r = 0. 255 P < 0. 001 . vitamin A is negatively correlated with IL-1β r = -0. 306 P < 0. 01 vitamin B6 is negatively correlated with IL-6 r = -0. 265 P < 0. 01 and vitamin C is negatively correlated with TNF-α r = - 0. 203 P < 0. 05 . Conclusion Different types of digestive system tumors exhibit distinct patterns of vitamin deficiencies. Clinically it is essential to develop corresponding nutritional supplementation plans based on their metabolic characteristics and to pay attention to the impact of inflammation on vitamin consumption.