Magnesium borate

MineralMagnesiumBest with a meal

What is it

Magnesium borate is a salt of magnesium and boric acid sometimes used as a combined source of magnesium and boron in supplements, though it is far less common than magnesium citrate, glycinate, or oxide.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Combined magnesium + boron support

Limited Evidence

Studies use individual magnesium and boron salts more than magnesium borate. The combined-salt approach has minimal direct clinical evidence.

How it works

Once dissolved, magnesium borate dissociates into magnesium and borate ions. Magnesium serves as a cofactor in hundreds of enzymatic reactions including energy metabolism and nerve function. Boron may influence bone, joint, and possibly hormone metabolism, though essentiality in humans is not firmly established. Magnesium absorption from this salt has not been well characterized vs. more common magnesium forms.

Dosage

Adult RDAs: magnesium 310-420 mg/day; boron has no RDA but a UL of 20 mg/day for adults. DSLD does not provide a median dose for magnesium borate specifically.

When and how to take it

Take with food to reduce GI upset. Separate from interacting medications by at least 2-4 hours.

1 commercial form

Compare the main delivery options and what they’re best suited for.

Magnesium borate

Uncommon supplement form.

Absorption profile not well characterized vs. common magnesium salts.

Safety

Magnesium at excessive doses causes diarrhea. Boron from supplements should be kept well below 20 mg/day. Acute or chronic boron toxicity can affect GI, neurologic, and reproductive systems.

Who should be cautious

Avoid high-dose boron in pregnancy. Caution in kidney disease (magnesium excretion is impaired). Discuss with a clinician if taking hormone therapies or antibiotics.

Interactions

Magnesium can reduce absorption of bisphosphonates, tetracyclines, fluoroquinolones, and levothyroxine; separate by 2-4 hours. Boron may modestly affect estrogen and testosterone metabolism.

Food sources

Green leafy vegetables, nuts, seeds (magnesium); fruits, nuts (boron)

Amount
varies
%DV
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Frequently asked questions

Is magnesium borate the best form of magnesium?⌄

No. Magnesium citrate, glycinate, and malate have better-characterized absorption and tolerability.

How much boron is safe?⌄

Adult UL is 20 mg/day. Most supplements provide far less; chronic high doses should be avoided.

References

Magnesium borate on Wikidata — Wikidata link

Magnesium borate (PubChem CID 21981398) — PubChem link

Magnesium borate on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Magnesium borate (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.