Well, I was looking for information on a sudden blackout I had today. I didn't completely faint or fall, I fought it hard to stay standing and find my way to a couch. My symptoms were, 1. I started to feel sick and nauseous. (I was standing, both feet and legs flat on floor and reading my IPad in kitchen.) 2. The nausea quickly turned to blurred vision and light-headed feeling. 3. When I sat down, I noticed my head/face was wet and sweaty. My Question, is whether this is a blood sugar issue? (I had not eaten and just finished 40 minute elliptical.) I am also a recovering Thyroid cancer patient. I am on 135 mcg synthroid daily. Thank you.