Not from.hiking specifically, but after 5vuears of mountain biking in hot climates, we discovered you need to drink a lot more water than you think you need. And add electrolyte replacements, not just salt, but also potassium, magnesium, etc. You have possibly run down your body's reserves from sweating. Eat what your body craves, buy a good quality electrolyte replacement specifically for sport, drink A LOT (We average about 1 litre per 2 hours exercise) and get your blood pressure checked
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