I suffered a miscarriage in March and an ectopic pregnancy in June. I took a home test yesterday (cycle day 28), which came back positive. I went in right away for a blood test. My nurse just called and said that my count was 18, which is very low so my doctor doesn't want to re-test me until next Wednesday to allow seven days in-between tests. I insisted that I get re-tested tomorrow (48 hours after the last test), and questioned why he wants me to wait so long. Her answer was that since my levels are so low, he doesn´t think I´m really pregnant.
My doctor told me the same thing when I had my ectopic pregnancy, at which time he thought I was having a "chemical pregnancy". This month I ovulated late, on cycle day 18 or 19. Could this cause such low levels? I just need to know if it's possible for this to be a healthy pregancy or if I should prepare for the worst.
You're right in that you need another HCG determination to see if the hormone level is rising normally (it doubles in 48 hours); however, your doctor is also right in wanting to wait a week. An 18 count is so low that doubling it to 36, which is also very low, may not be meaningful. The error inherent in such low measurements may make the results look falsely reassuring or worrisome.
A solid week should get you up into higher numbers where you can then employ the 48-hours-doubling guideline.