Mirena iud 3 years and cycles are 9-12 days long but light. recently got a ultrasound. diagnosed with menorrhagia. cycles were not long before iud. i thought the iud was suppose to shorten cycle not make longer. is the iud the cause of menorrhagia?

Menorrhagia is the medical term for heavy periods. It is diagnosed by your perception of menstrual bleeding not by sonogram. Many people have absent to light periods on a Mirena IUD. If you are not happy with your level of cycle control or bleeding patterns you may want consider trying something else.

https://www.medicalnewstoday.com/articles/birth-control-mirena-side-effects#side-effects Above are side effects. Inter-period spotting and in some longer periods are noted . It appears your side effects they are within the realm of Mirena side effects. Discuss your concerns with your gyn .