Although it is safe to use a cup with a IUD or a copper T, we suggest that you avoid using a cup and take advice from your gynecologist before doing so. The menstrual cup stays in its place due to the vacuum that is built around the rim. This vacuum might interfere with the thread of the IUD/copper T while we are sliding the cup downwards to empty it or remove it. This might result in the IUD being pulled out due to the vacuum. Keep in mind that this risk is purely theoretical.