Vitamin C (C) consists of reduced form L-Ascorbic acid (AsA) and oxidized form L-Dehydroascorbic acid (DAsA). It has been a research subject in nutrition and food science field whether the C activity of DAsA will be 1 or 0.5 when C efficacy of AsA is 1. In this study, we provided low-C diet to ten healthy females for three days until the experimental day. After that we divided them into AsA group and DAsA group, and orally administered 1 mmol of AsA crystal (176mg) and DAsA crystal (174mg). We measured the amount of C in their urine. The 24-hour total amounts of C in urine during the C lacking period were 9mg in AsA group and 5mg in DAsA group. After ingestion of C the amounts were 47mg in AsA group and 35mg in DAsA group. No statistical difference was found between both groups. The urine sampling was undertaken every 2 hours for 8 hours after ingestion of C. The 0-2 hour amount of C in urine in DAsA group was larger than that in AsA group. But other timezones did not show statistical difference between both groups.