I certainly hope you feel better soon! Hopefully in 5 days you'll be OK!

In the meantime, all the suggestions about hydrating, using an electrolyte solution in your water, getting plenty of rest, etc., are good. I nearly bonked out on a recent hike and was sure I would be too tired to drive home. Digging out my Hydralite (formerly Gookinaid) and adding it to my drinking water had me perked up within an hour!
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey