There is no proven “best” type of magnesium for both sleep and anxiety. Magnesium bisglycinate and magnesium L-threonate have shown some promising results for sleep, but the evidence is still limited, and neither has been proven better than other forms. For anxiety, magnesium may help some people, particularly those with low magnesium levels or higher stress, but research is not strong enough to recommend one specific form.
Studies of magnesium bisglycinate have found small improvements in insomnia symptoms, while magnesium L-threonate has been linked with improvements in some measures of sleep quality and daytime functioning. Older studies often used magnesium oxide, but this does not mean oxide is more effective.
Magnesium should not replace established treatment for persistent insomnia or anxiety disorders. Supplements can also cause diarrhea, nausea, or stomach cramps, and increase the risk of toxicity in people with impaired kidney function. They may also interact with medications such as antibiotics, diuretics, and drugs for osteoporosis.
Avoid starting high-dose magnesium on your own. If sleep problems or anxiety are frequent, severe, or affecting daily life, discuss them with a primary care doctor or mental health professional, who can also determine whether magnesium supplementation is appropriate.