You may also be a bit low on potassium, calcium or magnesium. When we lose water or urinate a lot, those minerals tend to get lost a faster rate as well and it can make you feel yucky or experience sore/cramping muscles. Check with your pharmacist or doctor first if you are taking blood pressure medications, but otherwise you may want to try supplementing with 200-400 mg. potassium and a calcium/magnesium supplement to see if it makes you feel better.