For some reason some people are coming here after Googling "Faint blue line on pregnancy test kit" or "Am I pregnant if there is only a faint blue line". Dont ask me why, I have no idea but, by way of helping those of you who googled it and ended up here.
If your only getting a faint blue line the chances are the test kit is not very sensitive. Pregnancy test kits work by measuring a hormone called Human Chorionic Gonadotropin (hCG). Not all test kits measure this in the same way, the more sensitive the kit the smaller the amount of hCG is needed to give an early test result and the less sensitive the kit the more hCG is needed.
When buying a test kit you should look on the box, somewhere it should say something like Sensitivity 20IU/L ( (milliInternational Units per Liter) or 50IU/L.. Basically the lower the number the more sensitive the test kit is. The common rule is the more expensive the Pregnancy test kit is the more sensitive it is.
If you're getting a faint blue line then you either don't have a very sensitive test kit or you're not as far along as you thought, if this is the case you should wait 2-3 days and try again to get a better more accurate result.
But then what do I know? I am a bloke and I'm not trained in Midwifery or Gynaecology, truth is I have no medical training at all. Saying that I can put a lasti-plast on your finger or knee if you graze or cut it.
I went here for the answer. :)