My husband has CFS. He is in in his early 30s, was fit and athletic for his whole life - he was a bodybuilder until CFS (specifically PEM and orthostatic intolerance) forced him to take a long hiatus from the gym. He has always eaten extremely healthy and is overall very lean. About 2 years ago, almost by accident, we learned that he was pre-diabetic. His fasting glucose was borderline but always within range (high 90s to 99), but the glucose tolerance test showed that he had insulin resistance and glucose intolerance. We were shocked, as were his doctors since he didn't have any risk factors. We made some small changes in his diet, and whenever possible walk 20-30 minutes after eating, which made a big difference. He bought several glucose monitors and regularly checks his glucose to keep tabs on it. Something we've come to realize is that his pre-diabetes comes and goes. He often has periods of time - months - where he can eat carb heavy meals without exercise and his glucose raises and lowers perfectly. His glucose will be predictably erratic during periods of time where he's in a CFS flare (a period of time where he's feeling extra crappy and more prone to PEM, so he is careful to eat lower carb since he often isn't capable of walking even 20 minutes during these periods). His blood glucose is also predictably erratic if he hasn't slept well the night before. I know from his endocrinologist that it is normal for blood sugar to be less controlled when people are sick or haven't slept well, but my understanding is that there is always an underlying problem (it is just more or less kept in check with drugs and dietary interventions). I can't seem to find anything about prediabetes that can exist one day and then disappear. At this point, we understand that his blood glucose issues are probably related to his CFS and is not strictly a metabolic disorder. Are there others on this board who have similar blood sugar issues that aren't constant? When his blood sugar is too high or doesn't lower properly, he often doesn't feel it, so I think it is likely there could be a lot of people with CFS/ME who have similar issues but have no idea.