There is no single “best” magnesium for everyone—your goal and tolerance matter. A practical principle is that forms that dissolve better in liquid tend to be absorbed more completely. Citrate, lactate, aspartate, and chloride often show higher bioavailability than magnesium oxide in small studies. Oxide may list a high amount of elemental magnesium, yet its lower solubility can limit absorption for some people. Form choice can also affect digestion: citrate may be helpful if constipation is a concern, while people prone to diarrhea often do better with gentler options. Chelated forms such as magnesium glycinate are commonly well tolerated in practice. The right choice depends on the intended use, dose, kidney function, and potential medication interactions.