Experience From - Matt Mahoney , Rich Schick , Karl King , Paul
Schmidt , Michele Burr ,  Matt Mahoney  Just to add to Suzi's
post. Warning signs of hyponatremia (low sodium): exhaustion and
weight loss (as with dehydration), except that your urine is
clear and frequent, every 15 minutes. Your hands, feet, and head
swell as water shifts to restore proper sodium concentration.
The swelling in the head leads to headache, dizzyness, and
staggering. Salty foods will taste very good.  After the Knight
Trail 50K last week, I walked another 10 miles with my wife who
was still competing. It was about 75 F and sunny, not hot by
Florida standards, but this time of year my heat training is not
like it is in the summer, so I lose more sodium when I sweat. I
recognized the early signs of hyponatremia, so at the next aid
station I mixed a spoonful of salt in a cup of water and drank
it. Over the next 15-30 minutes the symptoms disappeared and I
had no more problems for the remaining 1-2 hours of walking.
Rich Schick  I go