Vitamin C (L-ascorbic acid) is a water-soluble vitamin that humans cannot make, so it has to come from food or supplements.
Also known as: ascorbic acid.
ODS lists a Recommended Dietary Allowance of 90 mg a day for men and 75 mg for women (ages 19 and up), 85 mg in pregnancy and 120 mg while breastfeeding; people who smoke need 35 mg more. The Tolerable Upper Intake Level for adults is 2,000 mg a day.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. The FDA-approved drug form is Ascor, an ascorbic acid injection for short-term treatment of scurvy when vitamin C cannot be taken by mouth.
ODS says about 70 to 90% of vitamin C is absorbed at intakes of 30 to 180 mg a day, falling to under 50% above 1 gram a day. Blood levels from oral doses are tightly controlled: in Padayatty 2004, 1.25 g by mouth gave peak levels several times lower than the same amount by vein. ODS notes that high doses can cause diarrhea, nausea and cramps, and could worsen iron overload in hereditary hemochromatosis.
Vitamin C does not have one fixed half-life: it changes with the dose and with how saturated the body already is. A review (Lykkesfeldt 2019) gives about 2 hours in blood after high doses by vein, while the Ascor injection label reports 7.4 hours after 1 g by vein in a 3-person study, so we do not list one number. After a dose by mouth, levels peak in about 2 to 3 hours (Lykkesfeldt 2019); Dose Track uses 2 hours.
Numbers shown are the values Dose Track uses, listed only where they agree with the source above. Half-life varies from person to person and with injection site.