What’s the earliest you had HCG detected in blood test?

I know all about the two week wait and just wait until your period is late but I didn’t track ovulation this month and I’m still a few days away from my period starting and I have been feeling so nauseous the last few days and it lasts pretty much all day which is not normal. I am getting my thyroid tested tomorrow and wanted to throw in a blood pregnancy test just to see. We were not actively trying this month so I’d be shocked if I was (it took us awhile to conceive our first). Anyways sorry rambling, I was just curious if anyone had HCG defected on a blood test prior to a positive urine test?