Why did my period change on tamoxifen?

Menstrual changes are actually quite common when taking tamoxifen, as this hormone therapy can affect your cycle in various ways throughout treatment. The fluctuations you're experiencing don't necessarily indicate that the medication isn't working effectively - tamoxifen's cancer-fighting benefits aren't directly tied to specific menstrual patterns. It would be helpful to discuss these changes with your oncologist at your next appointment, as they can provide reassurance and monitor how you're responding to treatment overall.