Magnesium L-Threonate vs Glycinate: Which to Take?

Magnesium L-threonate and magnesium glycinate are both well-tolerated forms of magnesium, but they are studied for different goals. L-threonate is researched mainly for memory, focus and sleep quality and supplies less magnesium per dose. Glycinate delivers about twice as much magnesium per gram and is often chosen for relaxation and sleep support.

Key Takeaways

Magnesium glycinate is about 14% elemental magnesium by weight; magnesium L-threonate is about 7–8%.
L-threonate studies focus on cognition and sleep quality, while glycinate is a common choice for evening relaxation and sleep support.
Human research on both forms is small and short; most L-threonate trials were funded by ingredient suppliers.
The NIH upper limit for magnesium from supplements is 350 mg a day for adults, unless your doctor advises otherwise. It covers all your supplements combined.
Diarrhea, nausea and stomach cramping are the most common side effects of too much supplemental magnesium.
Talk to your healthcare professional before starting magnesium if you have kidney problems or take antibiotics, bisphosphonates, diuretics or acid-reducing medicines.

Magnesium L-Threonate vs Glycinate at a Glance

	Magnesium L-threonate	Magnesium glycinate (bisglycinate)
Form	Magnesium bound to L-threonic acid (a magnesium salt of L-threonate)	Magnesium chelated with two molecules of the amino acid glycine
Elemental magnesium per gram	About 75–80 mg (7–8%)	About 140 mg (14%)
What it is studied for	Memory, cognitive performance and sleep quality	Sleep quality and relaxation; also used to raise magnesium intake
Typical label doses	1–2 g of the compound a day, roughly 75–150 mg of magnesium	Varies by product; the 2025 sleep trial used 250 mg of elemental magnesium a day
Common side effects	Generally well tolerated in trials; loose stools or stomach upset are possible	Generally well tolerated; loose stools, nausea or cramping at higher intakes
Who it may suit	Adults interested in brain and focus support who accept a lower magnesium dose	Adults who want a gentle form that delivers more magnesium per capsule for an evening routine

What Is Magnesium L-Threonate?

Magnesium L-threonate is a newer form of magnesium. It was developed by researchers who wanted to raise magnesium levels in the brain. In a 2010 study in rats, published in Neuron, the compound raised brain magnesium and improved learning and memory tasks. Those were animal results, and they do not prove the same effect in people.

Human studies are more recent and still small. In a 2024 trial of 80 adults with self-reported sleep problems, 1 g a day of magnesium L-threonate for 21 days improved several sleep and daytime-functioning scores compared with placebo. A 2026 trial of 100 adults found that 2 g a day for six weeks improved overall cognitive scores and some self-reported sleep measures, but not sleep measured by a wearable ring. Both trials were funded by, or had authors from, companies that supply the ingredient. Keep that in mind when you read the results.

Because L-threonate is only about 7–8% magnesium, a 2 g daily dose supplies roughly 150 mg of magnesium. That is less than half of most adults' daily need. For a full look at tolerability, see our guide to magnesium L-threonate side effects.

What Is Magnesium Glycinate?

Magnesium glycinate, also called bisglycinate, joins magnesium to glycine, an amino acid. It is about 14% magnesium by weight, so a capsule can carry a meaningful amount of the mineral. Many people choose it because it tends to be gentle on the stomach. The NIH notes that magnesium carbonate, chloride, gluconate and oxide are the forms most often reported to cause diarrhea.

The best human evidence for glycinate and sleep is a 2025 randomized trial of 155 adults who reported poor sleep. Taking 250 mg of elemental magnesium as bisglycinate each day for four weeks modestly improved insomnia-severity scores compared with placebo. The researchers described the effect as small. People who ate less magnesium at the start seemed to benefit more. Fewer side effects were reported in the magnesium group than in the placebo group.

If you prefer this form, OPA Magnesium Glycinate capsules provide 250 mg of elemental magnesium per two-capsule serving. OPA Magnesium Glycinate Gummies provide 30 mg per gummy, which makes it easier to start low.

How to Choose Between L-Threonate and Glycinate

Your main goal is relaxation and sleep support: glycinate is the more practical starting point. It delivers more magnesium per dose and has a recent sleep trial behind it.
Your main goal is memory and focus: L-threonate is the form studied for cognition. The evidence is early, and the trials were small and industry-funded.
You want to raise your overall magnesium intake: glycinate supplies about twice as much magnesium per gram. Food matters too: leafy greens, legumes, nuts, seeds and whole grains are good sources.
You have a sensitive stomach: both forms are generally well tolerated. Starting with a lower dose taken with food can help.

Always compare products by elemental magnesium. The NIH explains that the Supplement Facts panel lists the elemental magnesium, not the weight of the whole compound.

Safety and Side Effects

The Tolerable Upper Intake Level (UL) for magnesium from supplements and medicines is 350 mg a day for adults, unless a doctor advises otherwise. This limit covers all supplemental magnesium combined. It does not include the magnesium in food, which healthy kidneys handle well.

Going above that amount can cause diarrhea, nausea and stomach cramping. Very high intakes, usually from large doses of laxatives or antacids, can lead to magnesium toxicity. The risk is higher when the kidneys do not work well, because they cannot clear the extra magnesium. If you have kidney disease, talk to your healthcare professional before taking any magnesium supplement. The same applies if you are pregnant or breastfeeding.

Interactions to Know About

The NIH Office of Dietary Supplements lists several medicine interactions that apply to all forms of magnesium:

Bisphosphonates (such as alendronate): take magnesium at least 2 hours before or after them.
Tetracycline and quinolone antibiotics (such as doxycycline or ciprofloxacin): take the antibiotic at least 2 hours before, or 4 to 6 hours after, a magnesium supplement.
Diuretics: some increase magnesium loss in urine, while potassium-sparing diuretics reduce it.
Proton pump inhibitors: long-term use, typically more than a year, can lower magnesium levels.

Very high doses of zinc from supplements (142 mg a day) can also interfere with magnesium absorption. If you take prescription medicines, ask your pharmacist or healthcare professional how to time your magnesium.

Frequently Asked Questions

Is magnesium L-threonate safe?

For most healthy adults, magnesium L-threonate appears safe at label doses. Trials using 1–2 g a day reported it was well tolerated. Its magnesium content stays well under the 350 mg daily upper limit for supplements. People with kidney problems, who are pregnant, or who take interacting medicines should check with a healthcare professional first.

What are the side effects of magnesium L-threonate?

The side effects are the same as for other magnesium supplements, mainly loose stools, nausea or stomach cramping, especially at high doses. Recent trials reported no significant adverse reactions. Very high total magnesium intake can cause toxicity, particularly with poor kidney function. Read more in our magnesium L-threonate side effects guide.

Is magnesium L-threonate a scam?

No. It is a real, well-defined compound with published human trials. The evidence is still early, though. Studies are small and short, and most were funded by ingredient suppliers. Be skeptical of claims that go beyond the research, and compare products by elemental magnesium, since L-threonate delivers less magnesium per dose than other forms.

Can you take L-threonate and glycinate together?

Yes, some people combine them, for example L-threonate in the morning and glycinate in the evening. Add up the elemental magnesium from both. Keep the total from supplements at or below 350 mg a day unless your healthcare professional advises otherwise. Watch for loose stools as a sign you are taking too much.

Which magnesium is best for sleep?

No single form is proven best. Magnesium glycinate and magnesium L-threonate both have small randomized trials that showed modest improvements in self-reported sleep quality. Glycinate supplies more magnesium per dose, which may matter most if your diet is low in magnesium. Good sleep habits remain the foundation.

How much magnesium should I take per day?

Adults need 310–420 mg of magnesium a day from all sources, depending on age and sex. Food should supply most of it. Supplements should not exceed 350 mg a day for adults unless a doctor recommends more. Check the elemental magnesium on the label and talk to your healthcare professional about your needs.

Sources

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.