Same as these ladies have said. With my first MMC, hcg was around 3000 at 5 weeks. Then it went up, but not by much, stopped going up and started coming down after it hit 5000s. 8 week scan showed fetal pole with no heartbeat. They didn't do measurements but definitely small for dates. Maybe around 6 weeks.
My second MMC. hcg was over 14,000 at 5 weeks. Only had it measured that 1 time. Then at my 10 week appointment, we found that my baby measured 9 weeks with no heartbeat. My hcg was measured to be around 31,000 at that time. Which means it had definitely been dropping for a while. I waited for my body to get the hint for two weeks. The day before the bleeding happened, my hcg was 5,000 or so. It took a little while after the miscarriage for it to come all the way down.