Skip to content
ezGLP
Toggle navigation menu
Sign in
All research profiles

Mineral

Magnesium

Prepared by the ezGLP team. Sources last checked . Profile reviewed .

Also known as Magnesium glycinate, Magnesium citrate, Magnesium oxide

Routes represented in the knowledgebase: Oral.

Educational overview

Oral salts differ in absorption and tolerability; parenteral magnesium is a monitored prescription treatment, especially in renal impairment.

Magnesium is an essential mineral and the fourth most abundant cation in the body, with roughly half of it held in bone and most of the remainder inside soft-tissue cells. It is a required cofactor for more than three hundred enzyme systems, including every reaction that consumes ATP, which circulates as a magnesium complex, and it participates in protein synthesis, neuromuscular conduction, and the regulation of blood glucose and blood pressure. Serum magnesium reflects only about one percent of body stores and is a weak indicator of status. Supplements supply the mineral as oxide, citrate, chloride, lactate, malate, aspartate, glycinate, or threonate salts, which differ in elemental content and solubility.

Deficiency biology is settled, and the clinical literature is strongest where magnesium acts as a drug rather than a supplement. The Magpie Trial, a randomised placebo-controlled study of more than ten thousand women published in the Lancet in 2002, showed that intravenous magnesium sulphate roughly halves the risk of eclampsia in women with pre-eclampsia. Supplement trials are far less conclusive. A 2020 Cochrane review of magnesium for skeletal muscle cramps found no clinically meaningful benefit in older adults and insufficient evidence for pregnancy-associated cramps, and a 2021 meta-analysis of oral magnesium for insomnia in older adults described the contributing trials as small and of low quality.

Magnesium spans three regulatory categories at once. Oral magnesium sold for nutrition is a dietary supplement in the United States and a food supplement in the European Union, with no pre-market review of effectiveness. Magnesium hydroxide, oxide, and citrate are also active ingredients in over-the-counter antacids and saline laxatives regulated under FDA monographs, so the same salt is a supplement or a drug depending on the claim the label makes. Magnesium Sulfate Injection USP is an FDA-approved prescription product indicated for replacement in magnesium deficiency, for addition to parenteral nutrition admixtures, and for preventing and controlling seizures in pre-eclampsia and eclampsia, with parenteral administration contraindicated in heart block or myocardial damage.

Oral magnesium products are stable at room temperature in a closed container away from moisture, while the injection is stored per its label and administered in monitored clinical settings. For a dose log or inventory record, the salt and its elemental magnesium content are more informative than tablet weight, since products of identical milligram strength deliver very different amounts of the mineral. Loose stools are the effect that appears first at high supplemental intakes and the basis for the tolerable upper intake level NIH publishes, which covers supplements and medicines rather than food. Kidney function matters because impaired excretion permits hypermagnesemia, and timing relative to quinolone and tetracycline antibiotics, levothyroxine, and bisphosphonates is worth recording.

Category
Mineral
Routes represented
Oral
Storage context
Follow the product label; store in the original container away from excess heat and moisture.
Authoritative overview

Published literature

No verified PubMed or DOI link is available for this entry.

Safety evidence

Common or reported: diarrhea, nausea, abdominal cramping.

Serious or important: hypotension, respiratory difficulty, arrhythmia, or cardiac arrest with severe hypermagnesemia.

Severe toxicity is especially relevant with renal failure or parenteral exposure.

Safety evidence source

Interaction evidence

These are general, pairwise evidence notes. Green identifies the potential-synergy category, while Lv3/Lv2/Lv1 communicates evidence strength; it does not guarantee benefit or cancel a safety warning.

With tetracycline or fluoroquinolone antibiotics

Safety flag

Oral magnesium can bind these antibiotics and reduce absorption of both products.

Interaction evidence source

Common questions

Is magnesium glycinate better absorbed?

Comparative data are thinner than the marketing suggests. A 2001 study of US commercial preparations found magnesium oxide poorly absorbed relative to chloride, lactate, and aspartate, establishing that salt form matters. Organic salts such as citrate and glycinate are generally more soluble and better tolerated than oxide, but direct head-to-head absorption studies of glycinate against other organic salts are few, and no form has been shown to produce better clinical outcomes.

Why does magnesium cause diarrhea?

Unabsorbed magnesium is osmotically active in the bowel and draws water into it, which is exactly the mechanism by which magnesium hydroxide and magnesium citrate work as over-the-counter laxatives. Poorly absorbed salts such as oxide produce the effect most readily. The NIH Office of Dietary Supplements identifies diarrhea, nausea, and abdominal cramping as the adverse effects that set the tolerable upper intake level for supplemental magnesium.

Is there an FDA-approved magnesium injection?

Yes. Magnesium Sulfate Injection USP is an approved prescription product for intramuscular or intravenous administration, indicated for replacement in magnesium deficiency, for addition to parenteral nutrition admixtures, and for the prevention and control of seizures in pre-eclampsia and eclampsia. Its label contraindicates parenteral administration in heart block or myocardial damage and describes monitoring of serum magnesium and deep tendon reflexes.

Does magnesium help with sleep or anxiety?

Evidence is limited. Systematic reviews of supplemental magnesium for self-reported sleep quality and anxiety describe small trials with varied designs and different salts, reaching mixed conclusions and rated as low certainty. A 2021 meta-analysis of oral magnesium for insomnia in older adults reached the same verdict. Magnesium is not an approved treatment for insomnia or anxiety disorders in any major jurisdiction.

Does magnesium interact with antibiotics or thyroid medicine?

Yes, by binding them in the gut. Magnesium forms insoluble complexes with quinolone and tetracycline antibiotics, reducing absorption of both, and magnesium-containing products lower the absorption of levothyroxine and of oral bisphosphonates. The NIH Office of Dietary Supplements lists these interactions, and separating administration times is the approach usually discussed with a prescriber or pharmacist.

Further reading

Summarised from published literature for reference only, with citations to the source. Evidence is graded as reported and is not a recommendation to combine, dose, or use any compound.

For personal tracking and education only. Not medical advice, diagnosis, or treatment, and not a medical device. Peptides may be prescription-only or unapproved where you live. Consult a licensed healthcare professional.