PIP: Blood vitamin A levels can be affected by the use of oral contraceptives (OCs). In a study conducted by Gal et al. in 1971 it was found that plasma vitamin A levels of OC users was significantly higher than in non-users for each of the evaluations during the menstrual cycle. Early observations regarding the experimental effect of OC on plasma vitamin A levels were supported epidemiologically by Smith et al. and Prasad et al. who again found that OC users have higher plasma vitamin A levels than non-users. The regular cyclic pattern of vitamin A concentration in blood during the menstrual cycle suggested an association between changes in sex hormones and changes in vitamin A levels. Yeung and Chan, examining whether the rise in plasma vitamin A was because of the estrogen or the progestogen component of the OC, found that the elevated levels of vitamin A observed in women OC users are due to the estrogen content in the steroid preparation. In general, it appears clear that OC treatment elevates blood vitamin A levels, but carotenese are not significantly affected. Under normal conditions, there seems to be no danger of vitamin A toxicity due to OC use, since the induced change in vitamin A levels still falls within the normal range and is accompanied by a corresponding change in retinol-binding protein (RBP). The observed increments have been about 50% in the rat and 35% in humans. Estrogen appears to be responsible for the enhancement of RBP levels that brings about a concomitant increase in blood vitamin A concentration.