Types of Magnesium for Sleep: Citrate vs Threonate vs Glycinate

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This article provides general information about magnesium supplement forms. Consult a physician or pharmacist before starting any supplement, particularly if you have kidney disease, take medications, or have a chronic health condition. The daily tolerable upper intake level for supplemental magnesium in adults is 350 mg per day, above which adverse effects (primarily diarrhea) are more likely.

Why the Form of Magnesium Matters

Magnesium is the fourth most abundant mineral in the human body and is involved in over 300 enzymatic reactions, including those regulating sleep, stress response, and neurotransmitter activity. The question "should I take magnesium for sleep?" is answered in our related guide. This article addresses the follow-up question that more Canadians are asking: which type of magnesium should I take?

The different "forms" of magnesium refer to the compound the magnesium is bound to. The mineral magnesium (Mg) is always the same element; what changes is the molecule it is paired with (glycine, threonic acid, citrate, oxide, malate, taurate, etc.). This pairing affects three key variables:

1. Bioavailability: How much magnesium actually gets absorbed through the gut and into the bloodstream
2. Tissue specificity: Whether the magnesium reaches specific tissues (particularly the brain) more effectively
3. Side effects: Whether the companion molecule causes its own effects (citrate and oxide can cause loose stools; glycinate is generally well tolerated)

All Major Forms Compared

8 min read

Magnesium Glycinate: The Top Choice for Sleep

Magnesium glycinate (also called magnesium bisglycinate) is magnesium bound to two molecules of glycine, a non-essential amino acid that also has calming properties of its own. This dual action is one reason glycinate is favoured for sleep and anxiety applications: you're getting the sleep-supporting benefits of magnesium plus the mild calming properties of glycine in the same supplement.

Why glycine matters: Glycine is an inhibitory neurotransmitter in the central nervous system and an agonist at NMDA receptors. Research published in Sleep and Biological Rhythms (2012) by Bannai et al. found that glycine supplementation before bed reduced daytime sleepiness, improved sleep quality scores, and decreased sleep onset latency in subjects with poor self-reported sleep quality. Magnesium glycinate delivers both magnesium and glycine in a single supplement.

Bioavailability: Amino acid chelates like glycinate are absorbed via amino acid transporters in the gut, which is a more efficient uptake pathway than oxide or inorganic forms. This results in higher and more reliable blood magnesium levels per mg of supplement compared to cheaper forms.

Digestive tolerance: Unlike citrate and oxide, glycinate does not have a notable laxative effect at typical sleep dosing ranges (100-400 mg elemental magnesium per day), making it suitable for daily long-term use.

Typical dose for sleep: 200-400 mg elemental magnesium glycinate taken 1-2 hours before bed. Note that a tablet labelled "500 mg magnesium glycinate" contains much less elemental magnesium than 500 mg, because the glycine makes up a significant portion of the weight. Check the supplement facts panel for "elemental magnesium" content.

Magnesium L-Threonate: The Brain-Targeting Form

Magnesium L-threonate (marketed as Magtein, developed at MIT) is a newer form that was specifically engineered to cross the blood-brain barrier, the selective membrane that controls what passes from the bloodstream into brain tissue. Most forms of supplemental magnesium raise blood magnesium levels but do not significantly increase brain magnesium concentrations. L-Threonate does.

Research published in Neuron (2010) by Slutsky et al. demonstrated that magnesium L-threonate increased brain magnesium levels and improved synaptic plasticity and cognitive function in aging rats, with subsequent human research showing improved memory and executive function in older adults with cognitive decline.

For sleep specifically: a pilot human study by Liu et al. (2016) in the Journal of Sleep Research found that magnesium L-threonate supplementation improved both subjective sleep quality and polysomnographic sleep efficiency. The mechanism proposed is that increasing brain magnesium levels helps regulate the activity of NMDA receptors involved in sleep architecture control.

The main limitation is cost: Magtein-brand magnesium L-threonate is significantly more expensive than glycinate or citrate, typically $50-80 CAD per month versus $20-40 CAD for glycinate at equivalent elemental dosing. For most people primarily concerned with sleep onset and quality, glycinate provides good value. For those with cognitive concerns alongside sleep issues, threonate is worth considering.

Magnesium Citrate

Magnesium citrate is magnesium bound to citric acid. It is among the most commonly sold forms in Canadian pharmacies, appearing in products like Natural Calm (the effervescent powder) and many standard tablet supplements. Bioavailability is substantially better than oxide but lower than glycinate in most comparative studies.

The primary practical concern with citrate is its dose-dependent laxative effect. At doses above 200-300 mg elemental magnesium, citrate reliably softens stools or causes loose stools in many people. This is exploited therapeutically (citrate is used medically for bowel preparation before colonoscopies), but it makes higher doses problematic for people using it purely for sleep. At doses of 100-150 mg elemental magnesium, the laxative effect is usually mild and tolerable for most people.

Citrate-form products like Natural Calm are taken dissolved in warm water, which makes them convenient and pleasant to take before bed , a ritual that itself can signal the body that sleep is approaching. This is a legitimate benefit that counts in practice, even if the form isn't the most bioavailable.

Magnesium Oxide: The Common but Inefficient Form

Magnesium oxide is the cheapest and most concentrated form by weight, meaning it delivers the most mg of magnesium per tablet. This is why it appears in many budget supplements and multivitamins. Unfortunately, its bioavailability is extremely low: a landmark bioavailability comparison study found that magnesium oxide was absorbed at a rate of approximately 4%, compared to 40-50% for citrate and comparable rates for glycinate.

This means a 500 mg tablet of magnesium oxide delivers approximately 20 mg of usable magnesium to the body. To get 200 mg of elemental magnesium absorbed from oxide supplements, you would theoretically need 5,000 mg of the supplement. At those doses, the laxative effect is pronounced and the GI side effects significant.

The main use case for magnesium oxide is as an antacid and short-term laxative, not as a nutritional magnesium supplement for sleep. If a supplement's label says "magnesium oxide" and lists 400 mg, that product is likely not meaningfully supplementing your magnesium levels.

Magnesium Malate, Taurate and Other Forms

Magnesium malate: Magnesium bound to malic acid. Malic acid is involved in the citric acid cycle (energy metabolism), and magnesium malate is sometimes used in fibromyalgia protocols for its potential role in reducing muscle pain and fatigue. For sleep, it has decent bioavailability and good tolerance, but less specific sleep research than glycinate. A reasonable choice for people dealing with both sleep issues and muscle discomfort.

Magnesium taurate: Magnesium bound to taurine, an amino acid with cardiovascular and neuroprotective properties. Emerging research suggests magnesium taurate may be particularly useful for blood pressure management and cardiovascular health. For sleep, the taurine component has GABA-mimetic properties, making taurate a reasonable choice for sleep with additional cardiovascular benefit. Less widely available in Canada than glycinate or citrate.

Magnesium chloride (topical): Sold as oil sprays, bath flakes, and transdermal patches. Proponents claim that topical magnesium is absorbed through the skin and raises blood magnesium levels. The evidence for this is mixed: some pharmacokinetic studies show modest skin absorption; others show it is primarily cosmetic. The relaxation benefits of a magnesium salt bath (Epsom salts are magnesium sulphate) likely involve a combination of modest mineral absorption, the warm water relaxation effect, and the ritual of a pre-bed bath, which itself lowers core body temperature and promotes sleep onset. Difficult to separate the variables.

Availability and Cost in Canada

In Canada, magnesium supplements require a Health Canada Natural Product Number (NPN) to be sold legally as natural health products. Most major forms are widely available:

• Glycinate: Available in most pharmacies and health food stores. Brands include Natural Factors, Organika, AOR, and Jamieson. Approximately $25-50 CAD per month at 200-400 mg elemental dosing.
• L-Threonate: Available at health food stores and online retailers. Primarily sold under the Magtein brand or licensed Magtein formulations. Approximately $50-85 CAD per month.
• Citrate: Most widely available. Natural Calm (powder), Jamieson, Sisu, and many others. Approximately $20-35 CAD per month.
• Oxide: Found in many budget multivitamins and basic supplements. Not recommended as a dedicated sleep supplement given poor bioavailability.

Related Reading

• Magnesium for Sleep: Does It Work and How Much to Take?
• Insomnia Symptoms and Natural Treatment Guide
• CBN and Cannabinol: Sleep Supplement Guide
• Melatonin Patches and Sleep Patches: Do They Work?
• Browse Mattresses at Mattress Miracle

Sources

• Abbasi, B., et al. (2012). The effect of magnesium supplementation on primary insomnia in elderly. Journal of Research in Medical Sciences, 17(12), 1161–1169.
• Bannai, M., et al. (2012). New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep. Sleep and Biological Rhythms, 10(3), 169–179.
• Slutsky, I., et al. (2010). Enhancement of learning and memory by elevating brain magnesium. Neuron, 65(2), 165–177.
• Schuchardt, J.P., & Hahn, A. (2017). Intestinal absorption and factors influencing bioavailability of magnesium. Current Nutrition and Food Science, 13(4), 260–278.
• Walker, A.F., et al. (2003). Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research, 16(3), 183–191.
• Health Canada. (2022). Magnesium: natural health product monograph. canada.ca