When comparing estrogen in the form of hemihydrate with estrogen valerate, especially in tablet form, the distinctions primarily revolve around their chemical composition, bioavailability, and how they’re metabolised in the body. Both are formulations of estrogen used in hormone replacement therapy (HRT) and they contain the same amounts of estrogen so it usually doesn’t matter which you are prescribed.

Chemical Composition and Form

• Estrogen Hemihydrate: Refers specifically to oestradiol (the biologically active form of estrogen) hemihydrate, meaning the oestradiol is crystallized with water molecules. It is a direct form of estrogen.
• Estrogen Valerate: Is an esterified form of estrogen, meaning the oestradiol is bound to the valeric acid to form oestradiol valerate. This formulation is a prodrug, which means it is converted into active oestradiol by the body after administration.

Bioavailability and Metabolism

• Estrogen Hemihydrate Tablets: Once ingested and absorbed into the bloodstream, estrogen hemihydrate does not require conversion and is immediately available as active estrogen. This can provide a more immediate effect on estrogen levels in the body.
• Estrogen Valerate Tablets: Requires conversion in the liver to oestradiol, the active form of estrogen. This conversion process means that the onset of action might be slightly delayed compared to hemihydrate forms. However, the esterification can also aid in a more prolonged release of estrogen into the bloodstream.

Usage and Efficacy

• Both forms are effective for hormone replacement therapy and are chosen based on clinical goals, a person's tolerance, and preference. The choice between them may also be influenced by how a person’s body metabolises estrogen, with some people responding better to one form over the other.

Dosage and Administration

• The dosing may vary between the two due to differences in their bioavailability and metabolism. For example, the dose of estrogen valerate might be adjusted to account for the conversion process and ensure the desired level of active estrogen is achieved in the body.

In summary, while both estrogen hemihydrate and estrogen valerate tablets aim to increase estrogen levels in the body, their differences in chemical structure, metabolism, and possibly the onset and duration of action can occasionally influence a the choice of which to have. The decision on which formulation to use is tailored to the individual’s needs. If you want to be recommended a specific type of estrogen, please ask your prescribing physician as the particular type will have to be specified on your prescription.