I found this information at http://www.americanpregnancy.org. If you are currently 13 DPO, you would be almost in the 4 wks. LMP timeframe, so an hcg of 43 is ok according to this chart! I know when I had my first pregnancy (a m/c) I was supposedly 6 wks. pregnant and my hcg was only 43. That was obviously too low. Now I am pregnant again and my first hcg levels (drawn 48 hrs. apart) were 495 & then 1776! I have been told that as long as your hcg is at least doubling every 48 hrs. the pregnancy is healthy & progressing well. If I were you, I would pay more attention to what today's hcg level is in relation to your level 2 days ago. I hope it doubles & that you have a happy, healthy 9 mos. ahead!
3 weeks LMP: 5 - 50 mIU/ml
4 weeks LMP: 5 - 426 mIU/ml
5 weeks LMP: 18 - 7,340 mIU/ml
6 weeks LMP: 1,080 - 56,500 mIU/ml
7 - 8 weeks LMP: 7, 650 - 229,000 mIU/ml
9 - 12 weeks LMP: 25,700 - 288,000 mIU/ml
13 - 16 weeks LMP: 13,300 - 254,000 mIU/ml
17 - 24 weeks LMP: 4,060 - 165,400 mIU/ml
25 - 40 weeks LMP: 3,640 - 117,000 mIU/ml
Non-pregnant females: <5.0 mIU/ml
Postmenopausal females: <9.5 mIU/ml