Going unconscious while staying upright?

What you are describing is abnormal. Yes, it could be due to low blood pressure or something called orthostatic hypotension. It can also be caused by low iron levels or anemia. It could also be a warning sign of diabetes or pre-diabetes. Whatever it is, you need to bring this to the immediate attention to your doctor. Print out this question and read it off to him/her so that you don't miss anything. And also, don't delay the appointment. Maybe if you can go first thing Monday that would be great. It's better to get things under control and figure out whats causing them than to wait or delay. Good luck! No worries, but definitely something you want to tell your doctor about fast.