Femmenessence is a herbal supplement and hasn't been approved by FDA yet.
It's safety and efficacy are not regulated
There is no data to suggest its interactions with any other drugs.
However, it works by stimulating the hypothalamus, pituitary and adrenal glands and affect hormones such as FSH, Estrogen, LH, Thyroid and Progesterone; there is a likely possibility of interactions between this and Synthroid.
Therefore, it is advised to avoid to use both of them simultaneously.
I suggest to discuss it with your doctor before starting it.
I hope this helps.
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