I'm hypo also. You need to take the mag supplement separately from the thyroid med. 3-4 hrs is recommended. Mag is best absorbed in small doses thru out the day so I take some morning noon and night.
I use 2 types because the mag is bound to a different chemical in each type. Mag glycinate is chelated with the amino acid glycine. This makes it highly absorbable. Great for insomnia, anxiety, depression, reduction in substance p (causes pain) etc.
Mag malate is combined with malic acid. Malic acid is good for muscle pain and energy production. I could just use the malate but I have a lot of muscle spasms and serious insomnia so the glycinate is more helpful for that. It's a great combo along with the mag oil.