Pill form The most commonly prescribed estrogen used by doctors in the U.S. is Premarin, derived from mare's urine. All conjugated estrogens taken by pill or capsule are advised to be used in conjunction with a progestin, unless the uterus is already removed. As noted earlier, this has the disadvantage of causing a woman to continue having periods. However, it is not completely certain if progestin's opposition to estrogen reduces or eliminates the risk of uterine cancer when administered in this way. The more normal schedule is to take estrogen for the first 25 days of the month, and then progestin for a shorter time, usually 10-14 days.
Different doctors have different regimes.
The most common complaints when taking HRT in this way are fatigue, weight gain and irritability. If a woman does not have a uterus, she should take a few days off each month from taking estrogen, but doctors rarely advise her to take progestin. If a woman is producing quite a lot of estrogen on her own during her menopause or peri-menopausal phase, sometimes doctors advise taking progestin alone to keep excess uterine lining from building up. If Premarin or other oral estrogens are used, they become concentrated in the digestive tract, where they are transformed chemically. Therefore the percent which is biologically active, or available for use is considerably less than what was ingested.