I see it mentioned all over the internet that doubling can slow to 72-96 hours at this point without a source in sight. Anecdotally, it looks like a lot of healthy pregnancies maintain a higher rate for a bit longer.
My doubling was initially under 48hours and then tanked to 66 hours after 1200.
Edit:
Just to add, I found this study on doubling time where they found that the "mean and upper 85% confidence limit of DT over this range [0-6500 mIU/ml] in hCG concentration were 2.11 and 2.24 days, respectively" and "However, reported normal values have ranged from1.4 to 3.5 days."
I also found this study which shows the mean between 1200-6000 was 2 days, and using an 85% confidence limit, doubling time >2.6 days would be considered abnormal between 1200-6000miUL/ml.
My doubling was initially under 48hours and then tanked to 66 hours after 1200.
Edit:
Just to add, I found this study on doubling time where they found that the "mean and upper 85% confidence limit of DT over this range [0-6500 mIU/ml] in hCG concentration were 2.11 and 2.24 days, respectively" and "However, reported normal values have ranged from1.4 to 3.5 days."
I also found this study which shows the mean between 1200-6000 was 2 days, and using an 85% confidence limit, doubling time >2.6 days would be considered abnormal between 1200-6000miUL/ml.