Finger prick test to measure blood glucose

Patient: I almost passed out at work today and the paramedics came and gave me a prick on my finger and the strip came out blue. My question is what are they testing for because i had recently somked som marijuana and i am afraid it will be detected?

Doctor: The finger prick test with colour change you describe, most likely represents a blood glucose measurement. A blood gluco se level would often be measured by paramedics, because a low blood sugar level may cause collapse and coma, and also an extremely high blood glucose level may cause collapse and a reduced conscious level.