BACKGROUND: Although fatigue is the most common symptom in primary care, both doctors and patients tend to overlook it. According to one study, 27% of the adults felt fatigued for one week and 6% of the adults complained of unexplained fatigue for over two weeks. Stress play an important role in the etiology of fatigue. Thus, antioxidants are currently taken by people who complain of fatigue. Vitamin C is one of the most common antioxidants. We intend to find out whether intrarenous vitamin C is really helpful or not in people who complain of fatigue. METHODS: We have investigated 19 outpatients who chiefly complained of fatigue and visited the department of family medicine at one university hospital from July 1, 2004 to Nov 30, 2005. The patients were treated by Vitamin C 10g and Vitamin B complex injection for 4 weeks, and they conducted a questionnaire survey concerning the severity of symptom before and after injection. The questionnaire with 9 questions consisted of 7 score index. The results were statistically analyzed with Wilcoxon Signed Ranks test and a P-value under 0.05 was considered significant. RESULTS: Three patients were males and 16 patients were females. The average age group was 47.7+/-13.6 years. While the fatigue severity score of the patients before vitamin C injection was 5.2 (3.0~7.0), the fatigue severity score after injection was 3.3 (1.4~4.8), which was significantly decreased (P<0.0001). CONCLUSION: We think that the vitamin C intravenous injectioned to people who complained of fatigue was helpful.