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The test ranges are not that informative for serum magnesium.

Very low and very high levels, are useful with blood work, but the middle ranges can still be deceptive, and you could still need more.

When you get laxative action, that shows that the mag is not being absorbed, and is acting like a laxative.

You could add in a topical form, lotion, or cream.

Kirkman cream (on the net)

Epsom-It (on the net)

or CVS epsom lotion if your CVS still has it. (They stopped offering this wonder lotion because of poor sales response-- which is sad..and reflective of how poorly educated the US consumer base is about magnesium).

I rub mine on the pain/swelling areas, and also on my arms concentrating on the under portion and wrist where the skin is the thinnest. I find topical works very well for me. A nickel sized dollop on each arm...

You might find additional improvements this way.