Are There Any Harmful Effects Of Mirena Coil?

i have been advised to have a marena coil fitted as i have periods that are only two week apart and have suffered with aneamia over the past 12 months, i am on iron tablets but i wont have to take these once the marena coil is working, i have never taken any form of contraceptive i am 43 years old i am worried about effects of the marena coil