Let's start with how much water are you drinking usually in a day. My goal is 64 ounces a day - that's my minimum amount - warm days I easily drink up to 128 ounces daily.
Have you talked with your doctor about
this yet? If so, what did they have to say? Also, are you sure that it's dehydration or are you just urinating a lot? Sorry, but there is a difference and I was hoping to clarify.
Sodium usually creates a situation where the body holds more fluid, not expel more fluid, which is why it would be best to start with talking to your doc, if you haven't yet.
There are many forms of magnesium available. I like using this explanation of the different types to help me choose the ones that are right for my needs:
www.globalhealingcenter.com/natural-health/types-of-magnesium/ Also, have you looked into using an electrolyte solution for a while to ease the dehydration?