I'm not an expert, but I'll post my two cents since I've been researching reactive hypoglycemia as well. I recently had an OGTT w/insulin check and my two hr glucose dropped to 55 (from 66 at the 1hr). Anyway, the 55 was flagged as being low. Now, what occurred with you could be totally normal, I don't know...I don't want to freak you out with my next statement because it might not apply, but I have read that reactive hypoglycemia *can be* associated with hypothyroidism and adrenal issues. In my case, I think it could be that my hypothyroidism is being undertreated. Hope this helps some.
I suffered an episode last week where after dinner (2 hours) my sugar dropped like a rock. We called 911, and by the time the paramedics showed up, I had been eating glucose tablets, and was up to 52, they followed with a tube of glucose liquid, and I rose to 120 by the time I got to the hospital.
After a 2 day "Hangover" (How i feel after an episode) things seem stable.
I also believe these attacks are tied very closely with some sort of adrenaline issue as I have horrible Panic Attacks. The 2 (adrenaline and insulin) are very closely related.
"all of the doctors I have seen so far say it is normal for people to have nausea when they wake up."
I highly doubt if they wake with nausea, I don't.
"My headache / glucose threshold is between 70 and 80 mg/dL."
What does this mean?
You should be seeing an Endocrinologist for answers and treatment.