Form Comparison

Magnesium Glycinate vs Magnesium L-Threonate

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

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Quick verdict. Glycinate is the better choice for correcting low magnesium: it delivers about 70% more magnesium per gram of compound (14.1% vs 8.3%) at a fraction of the cost. Threonate's case rests on rodent brain-uptake data and one small industry-funded cognitive trial in older adults. Choose threonate only if that specific evidence is what you are paying for.

Side by Side

Magnesium Glycinate Magnesium L-Threonate
Elemental content 14.1% elemental magnesium 8.3% elemental magnesium
Absorption High Moderate
How it is absorbed Magnesium bound to two glycine molecules. The chelate stays soluble across intestinal pH, and absorption proceeds through the same paracellular and TRPM6/7 channel routes as other soluble salts; head-to-head human data against citrate are limited. 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 general repletion, sleep support, sensitive stomachs cognition (limited evidence)
Side effects The least likely form to cause loose stools at typical doses. Gentle at the low elemental doses involved.
Cost Moderate High
Also called magnesium bisglycinate, magnesium bisglycinate chelate, chelated magnesium Magtein, magnesium threonate
Labels in index 660 95

When to Choose Magnesium Glycinate

Choose magnesium glycinate when GI tolerance matters most or the dose is taken at bedtime. 200 mg elemental magnesium as bisglycinate delivers roughly 1.2 g of glycine, which has its own small trials for subjective sleep quality. Buffered products blend in oxide to raise elemental content; check the panel.

Magnesium Glycinate

Best general-purpose form when tolerance matters. Well absorbed and the least likely to loosen stools.

What to look for: Bisglycinate as the only form on the panel (not buffered with oxide), with elemental mg per serving stated. USP or NSF verified.

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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.

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Products on Titrate

In Titrate's index of NIH label data, 660 labels in the Magnesium category list magnesium glycinate 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.