According to @henrythepharmacist, a compounding and nutrition pharmacist expert on TikTok, certain supplements should not be taken at the same time as magnesium since they can interfere with each other.
One of these is iron. Magnesium and iron compete with each other for absorption, he says, so you want to leave at least four hours in between them. Zinc also competes with magnesium for absorption in the same way.
Finally, he says calcium and magnesium don’t do well taken together. Ironically, they are often included together in the same pill, but he explains that these two minerals also compete with each other for absorption. He advises taking them separately and avoiding the combined formulas.
Finally, he mentions multivitamins as being problematic since they generally contain at least some of these four minerals. He suggests spacing out when you take your magnesium and multivitamins.