A dosage of 1 mg/day oral estradiol valerate has been found to produce approximate circulating concentrations of 50 pg/mL estradiol and 160 pg/mL estrone, while a dosage of 2 mg/day results in circulating levels of 60 pg/mL estradiol and 300 pg/mL estrone. These concentrations of estradiol and estrone are comparable to those observed with 1 and 2 mg/day oral estradiol. A review of selected studies reported a range of mean peak estradiol levels of 24 to 140 pg/mL occurring 1 to 12 hours after administration of 2 mg oral estradiol valerate. A study found that, in accordance with their differences in molecular weights, oral estradiol produced higher levels of estradiol than oral estradiol valerate. Likewise, other studies found that levels of estradiol and estrone are very similar after oral administration of roughly equimolar doses of estradiol (1.5 mg) and estradiol valerate (2 mg). A study of high-dose oral estradiol valerate found levels of estradiol of about 250 pg/mL after a single 10-mg dose in three women.