How long did it take for everyone's levels to return to negative after a miscarriage? I had a missed miscarriage 15 days ago and I'm still getting obviously positive tests. I have not had my levels checked by my OB yet. I have an ultrasound on July 12 to make sure I expelled all the tissues. Here's the test that I just took. I was 11+4 when I discovered I had a MMC baby stopped growing at 8 weeks.