Woohoo! Hcg at 512 today. I found an online calculator that computed my doubling time as 1.72 days or just over 41 hours. Sounds good to me. I'm still pregnant, even though I can't tell. I have an u/s scheduled for August 3rd, so I'll remain PUPO for at least another two weeks. Meanwhile, I'll research how likely I am to see a heartbeat at approximately 6 weeks 4 days.
The nurse who called with my beta number also provided me with a wonderful resource. I don't know if it's available outside MA, but if you have a health-care product that you are thinking of using and want to make sure its ingredients are safe for pregnancy, call 800*322*5014. You should have specific items' ingredients in front of you in case the actual item is not in their database.
I've never been so happy not to eat sushi or drink beer!