I had high HCG results (not as high as yours, but higher than normal), too -- and my 'doubling time' was also faster than 48 hours (I think it was 35 hours). One possibility is that your dates are a bit off -- that is, you are more than 6 weeks pregnant. In my case, this seems to have been true -- my current due date is about 10 days sooner than my original due date (and I'm not carrying twins). Another possibility though, as others have mentioned, is twins. I was also told that there is just some natural variability in these numbers -- both between different moms and between pregnancies (same mom). I feel for you -- I was pretty nervous when the nurse told me, too. But, as I said, in my case it was just a matter of dates (and normal variation) --- and all was fine. Hang in there.