Hcg levels

Stacy

Help i got positive Pregnancy test at 10 dpo and i had my first hcg beta at 11 dpo.

11 dpo- HCG 15

13 dpo-HCG 15

15 dpo-HCG 37

Should i be concerned that the level didnt double the first time?

Update:

18 dpo-HCG 79.5