It has to do with tissue level deficiency, which is what you should be really concerned with.
99% of your magnesium is in the tissues, so don't bother with your serum levels.
BTW you can buy magnesium chloride flakes and mix them with water
50/50 to make your own magnesium oil.
I've been doing this for years and it really works for me.
Try every other day, avoid sensitive parts of your body and after
You dry yourself, use a long natural bristle brush and give yourself a
Lymphatic massage. You will fell like a new ..person, lol!
Cheers!
Niko