High hcg level

  At 5 weeks, 2 days from LMP, my first hcg level was 396.  The dr thought this was a little on the low side so he ordered another blood test in one week.  The following week my hcg level was 6312.  THe dr thought that was a little high.  He ordered an ultrasound to r/o ectopic pregnancy or multiples.  The ultrasound showed a uterine pregnancy, one baby.  Is there any other reasons why my hcg levels would have multiplied too quickly?  Should I be concerned?  My dr just said "That's good news - see you in 3 weeks for your first prenatal"  but gave no explanation for the values.  What is your opinion?   Thank you!!!
Dear Bridget:
There is no meaning to an hCG level by itself. It is the pattern of change that is important. hCG rises with a doubling time of 2-3 days. You report two values, one week apart, with a doubling time that conforms to 8 days. This is a normal pattern. The reassuring ultrasound images further demonstrate that this is a normal pregnancy.
Keywords: hCG, early pregnancy
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