When does the rise of hcg levels start slowing down?

Laura

Hi guys, so my hcg was around 40,000 at 6 weeks or so. It was doubling every 24-36 hours I think before that. I got a test at 8 weeks 5 days after they saw the heartbeat on ultrasound and it was 120,000.

Should it have been rising faster during that time or is it normal for the rise in hcg to slow down?