Magnesium

Overview

Magnesium is a mineral your body needs for hundreds of basic jobs, including energy production and the activity of enzymes involved in oxidative phosphorylation (how your cells make usable energy). It's one of the most-studied over-the-counter supplements, and researchers have tested it for several very different everyday problems, with mixed results depending on what you're using it for.

For muscle cramps, a large Cochrane review found magnesium supplements don't clearly reduce cramp frequency or intensity compared with placebo in the general population¹. For muscle fitness — things like grip strength, leg strength, and muscle power — a meta-analysis of randomized trials found a modest positive effect, particularly in older adults and athletes². For sleep, a systematic review in older adults with insomnia found some improvement in sleep quality but noted the evidence base is still limited³. For brain health, a 2024 review of trials and cohort studies looked at how magnesium intake and blood levels relate to cognitive outcomes, finding associations worth further study rather than definitive proof⁴. And in pregnancy, magnesium sulfate (an injectable form, not the oral supplement) is well established for preventing eclampsia (seizures linked to pre-eclampsia) in at-risk women⁵.

Dosage

The reviewed studies did not report a single consistent oral dosage across trials — magnesium form and dose varied by study and outcome studied. What the research does clarify is bioavailability: organic magnesium formulations (e.g., citrate, glycinate-type compounds) appear to be absorbed better than inorganic forms (e.g., oxide), and absorption percentage is dose-dependent, meaning higher single doses tend to be absorbed less efficiently as a proportion⁶. For eclampsia prevention, magnesium sulfate was used as an intravenous/intramuscular medical treatment in the pooled trials (over 11,000 women), a fundamentally different context from an oral supplement and not a self-administered dose⁵.

Interactions

A safety database lists documented interactions between magnesium and: calcium supplements, potassium, adenosine triphosphate, manganese, insulin, vitamin D, fluorides, magnesium sulfate, acetylcholine, and edetic acid. The reviewed studies did not detail the clinical significance or direction of each of these interactions, so anyone taking these substances or medications alongside magnesium supplements should discuss it with a doctor or pharmacist.

Traditional Use

Magnesium is an element, and no traditional system has a concept of it — the metal was first isolated in 1808, long after these texts were written. What the older systems do have is an answer to the complaint magnesium is most often bought for today: the muscle that seizes up. Read that way, the record is unusually clear, and mostly unusually unfavourable.

What biohacking says

Evidence Strength

Magnesium is backed by six meta-analyses, which is a strong volume of pooled evidence — but the picture is genuinely mixed depending on what you're hoping it will do. The case for magnesium sulfate preventing eclampsia in pregnancy is well established, drawn from trials covering over 11,000 women. Evidence for muscle fitness is moderately supportive, evidence for sleep and cognition is preliminary and needs more research, and evidence for muscle cramps specifically leans negative. This is a good example of why "magnesium" isn't one single question — the answer depends heavily on the specific use case.