Irregular vaginal bleeding is the most common side effect of Mirena. This is caused by the effect of progesterone, and spotting will occur with any intrauterine device or medical contraceptive method, not Mirena. Le's patent. If this happens to you after wearing the ring, don’t worry too much. If the amount is not large, it will not cause anemia, and there is no need for special treatment. As time goes by, the bleeding will gradually get better. If you are really worried, you can also go to the hospital to see a doctor for a checkup. If everything is normal, you should not need to take medicine.