Form Comparison

Magnesium Chloride vs Magnesium L-Threonate

How magnesium chloride and magnesium L-threonate differ in elemental content, absorption, tolerance, and cost.

This page contains affiliate links. Titrate earns a small commission when you purchase through them, at no cost to you. This does not affect our recommendations.

Quick verdict. Absorption evidence is stronger for magnesium chloride (rated high) than for magnesium L-threonate (rated moderate), though the gap reflects thinner data more than demonstrated poor absorption. Choose magnesium chloride when you prefer a liquid or slow-release tablet. Choose magnesium L-threonate when you specifically want the form studied for cognition and accept thin evidence and high cost.

Side by Side

Magnesium Chloride Magnesium L-Threonate
Elemental content 12% elemental magnesium 8.3% elemental magnesium
Absorption High Moderate
How it is absorbed Highly soluble inorganic salt. Absorption was equivalent to lactate and aspartate and far above oxide in Firoz and Graber 2001. Threonate is a vitamin C metabolite. In rodents it raised cerebrospinal fluid magnesium more than other salts; human brain uptake has not been directly measured.
Typical dose 100-350 mg elemental magnesium daily 1.5-2 g compound daily (about 104-144 mg elemental)
Common uses liquid supplements, slow-release tablets, electrolyte drinks cognition (limited evidence)
Side effects Bitter in liquid form. Slow-release tablets are well tolerated. Gentle at the low elemental doses involved.
Cost Moderate High
Also called magnesium chloride hexahydrate Magtein, magnesium threonate
Labels in index 58 95

When to Choose Magnesium Chloride

Choose magnesium chloride when you prefer a liquid or slow-release tablet. Topical magnesium oil is chloride; transdermal absorption is not established.

Magnesium Chloride

Choose magnesium chloride when you prefer a liquid or slow-release tablet.

What to look for: Magnesium Chloride named on the Supplement Facts panel, with the amount per serving stated.

Find on iHerb Affiliate link

When to Choose Magnesium L-Threonate

Choose magnesium L-threonate when you specifically want the form studied for cognition and accept thin evidence and high cost. Human cognitive evidence is one small industry-funded RCT (Liu 2016). It delivers little elemental magnesium per dollar, so it is a poor choice for correcting a deficit.

Magnesium L-Threonate

The only form studied for cognition, on thin and industry-funded evidence. Poor value for correcting a deficit.

What to look for: Magtein (the patented form) with about 144 mg elemental magnesium per 2 g daily serving.

Find on iHerb Affiliate link

Products on Titrate

In Titrate's index of NIH label data, 58 labels in the Magnesium category list magnesium chloride and 95 list magnesium L-threonate.

Open supplement search

Supplement Search loads one category at a time. Choose the Magnesium tab, then type a form such as "bisglycinate" under Must contain, or a form to avoid under Must not contain.

Related

References

NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.

Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001;14(4):257-262.

Kappeler D, et al. Higher bioavailability of magnesium citrate as compared to magnesium oxide shown by evaluation of urinary excretion and serum levels after single-dose administration in a randomized cross-over study. BMC Nutr. 2017;3:7.

Pardo MR, et al. Bioavailability of magnesium food supplements: A systematic review. Nutrition. 2021;89:111294.

Zhang X, et al. Effects of Magnesium Supplementation on Blood Pressure: A Meta-Analysis of Randomized Double-Blind Placebo-Controlled Trials. Hypertension. 2016;68(2):324-333.

Holland S, et al. Evidence-based guideline update: NSAIDs and other complementary treatments for episodic migraine prevention in adults. Neurology. 2012;78(17):1346-1353.

Garrison SR, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020;9(9):CD009402.

Liu G, et al. Efficacy and Safety of MMFS-01, a Synapse Density Enhancer, for Treating Cognitive Impairment in Older Adults: A Randomized, Double-Blind, Placebo-Controlled Trial. J Alzheimers Dis. 2016;49(4):971-990.