Does grapefruit affect Mirena

Yes. However, grapefruit contains a compound that slows the absorption of estrogen hormones. If you eat too much of it, it can interfere with your Birth Control.
Yes. It can lead to having increased estrogen levels.

There are a few immediate side effects, such a breast soreness and nausea, but if there is prolonged exposure, it can greatly increase your chances of developing Breast cancer.
Birth control methods like the pill, shot, patch, ring, and IUD are not affected by grapefruit.