Thanks for replying.
Do you have hypoglycemia for long time?
Is your blood pressure also low?
If that's the case, I will suggest a morning time cortisol level check to rule out any adrenal gland insufficiency.
Also, as a substitute of endoscopy, a CT scan of the abdomen with contrast or a MRI abdomen with contrast can be considered as part of initial evaluation of liver, pancreas, gallbladder, stomach and intestine.
For endoscopy, you are allowed to drink clear liquids which can include glucose water, clear soup, pedialyte.
Usually 12 hours fasting ( no solids) should be ok.
Please reply back if you need any further clarification.
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