Hi Colely,

I've been looking into turkey tail and have learned it's contraindicated with tamoxifen.

Here's info from VeryWell Health:

Certain medications may interact with turkey tail mushrooms, including:

Certain anticancer drugs: Compounds found in turkey tail mushrooms can change how certain anticancer drugs (e.g., cyclophosphamide, tamoxifen) are processed and removed from the body, which may alter the efficacy of the anti-cancer drug and cause more side effects.
Diabetes medications: Turkey tail mushrooms may lower blood sugar levels too much in people taking diabetes medications.
Other herbs and supplements that lower blood sugar: Any herbs and supplements known to lower blood sugar (e.g., aloe, cassia cinnamon) should be avoided to prevent blood sugar levels from dropping too low.

And here's from WebMD:

Moderate Interaction

Be cautious with this combination
Cyclophosphamide interacts with TURKEY TAIL MUSHROOM

PSP, a chemical found in turkey tail mushroom, might change how quickly cyclophosphamide is removed from the body. This might alter how effective it is, and cause more side effects.
Medications for diabetes (Antidiabetes drugs) interacts with TURKEY TAIL MUSHROOM

Turkey tail mushroom might lower blood sugar levels. Taking turkey tail mushroom along with diabetes medications might cause blood sugar to drop too low. Monitor your blood sugar closely.
Tamoxifen (Nolvadex) interacts with TURKEY TAIL MUSHROOM

Taking turkey tail mushroom with tamoxifen might change the way that tamoxifen works in the body or reduce the effects of tamoxifen.

Minor Interaction

Be watchful with this combination
Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates) interacts with TURKEY TAIL MUSHROOM

Some medications are changed and broken down by the liver. PSP, a chemical found in turkey tail mushroom, might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

This board won't let me post direct links as I just joined, but you can easily find these results by googling "turkey tail tamoxifen."

Wanted to share in case you are still taking both, as well as let others know.

Take good care, and thanks for sharing about the clinical trial!