Will consuming cannabis before a blood test to see if I have thyroid issues mess with the results?

I'm (30F) going for some blood tests for potential thyroid issues for the first time in my life. I completely forgot about it today and let's just say I indulged in the devil's lettuce before remembering. My appointment is in 4 hours. Should I call to cancel? It was really tough to get, so I hope not but I will if I have no other choice.