Side effects that occur with bio-identical hormones are directly related to dose and balance. Dose can be related to the strength of the preparation but also to the form and the ability of the individual to absorb the preparation. The dose of one hormone may be appropriate but if its relationship to the other hormones is not correct symptoms may occur.
The form of the preparation may carry different benefits e.g. oral progesterone can make one sleepy whereas progesterone applied as a topically or vaginally is unlikely to have the same result. This can be an advantage if one is having difficulty falling asleep but a disadvantage if this results in daytime sleepiness.