I have low laying sodium 135-138 how quick during workout or drinking too much can they fall? i get cold during workout and dizzy after drinking a lot

Hyponatremia: Low sodium can occur rather quickly with excessive salt loss from perspiration,vomiting,diarrhea,excessive urination or from dilution due to drinking excessive amounts of water. Slower causes are from glandular problems like adrenal or pituitary problems. So the two mechanisms are loss of sodium and retention of too much water which dilutes the sodium level.