Magnesium Glycinate vs Citrate vs Oxide (and Buffered vs Non-Buffered)

Magnesium glycinate is the form most people pick for an evening routine because it's usually gentle on the stomach. Magnesium citrate is well absorbed too, but it pulls water into the bowel, so it has a mild laxative effect. Magnesium oxide packs the most magnesium into each tablet, yet little of it is absorbed and it's the form most likely to loosen stools.

This guide has a side-by-side table, what each form is actually good for, a quick take on malate, threonate and taurate, and the part most comparison pages skip: how "buffered" glycinate mixes these forms together, and how to catch it on a label.

Magnesium glycinate vs citrate vs oxide at a glance

People rarely see the first row, which is how much magnesium (Mg) you get from 1,000mg of the compound. Magnesium is always bound to something, and that partner decides how much of the capsule is actually magnesium. These figures are approximate, because the exact salt and its water content vary by supplier.

Our own label is a real example of the glycinate column: 1,700mg of magnesium bisglycinate supplies 200mg of elemental magnesium.

Magnesium glycinate: the gentle one

Magnesium glycinate is magnesium bound to glycine, a small amino acid. Chemists call it bisglycinate because each magnesium atom holds two glycine molecules. Glycinate, bisglycinate and diglycinate all name the same compound, and our guide to magnesium glycinate vs bisglycinate goes into the naming.

People like it because it dissolves well and a lot of them find it easy on the stomach. In a small study of people who'd had part of their intestine removed, magnesium diglycinate was absorbed better than magnesium oxide (Schuette and colleagues, 1994). The downside is bulk. Glycine takes up room, so a real 200mg dose usually means two to four capsules.

“I remember looking at magnesium labels and realizing that not all forms of magnesium are the same. I wanted something that was well absorbed and gentle, so when we created NO. 04, magnesium glycinate was the form I felt best about using.”

Skotie Rae, RN, founder

Magnesium citrate: well absorbed, with a laxative edge

Magnesium citrate is magnesium bound to citric acid, and it's one of the best-studied forms. In a 60-day randomized trial of 46 healthy adults, citrate raised blood magnesium more than an amino acid chelate or oxide at the same 300mg daily dose (Walker and colleagues, 2003). An earlier study found citrate was far more soluble than oxide and produced a much bigger rise in urinary magnesium, a common way to measure absorption (Lindberg and colleagues, 1990).

The catch is that citrate pulls water into the intestine. At higher doses that makes it a laxative, and liquid versions are sold for exactly that. At everyday supplement doses, some people notice nothing and some notice more bathroom trips than they wanted.

Magnesium oxide: a big number on paper

Oxide is the densest form. About 60 percent of its weight is magnesium, so a small, cheap tablet can print a big number. That's why it shows up in antacids, laxatives and budget multivitamins. The NIH Office of Dietary Supplements notes that forms that dissolve well in liquid are absorbed better, and that citrate, aspartate, lactate and chloride tend to be more bioavailable than oxide. In one comparison of U.S. commercial preparations, oxide had a fractional absorption of about 4 percent (Firoz and Graber, 2001).

Oxide isn't dangerous at normal doses, and it has real uses. It just gives you the least usable magnesium per milligram on the label, with the most chance of an upset stomach.

What about malate, threonate and taurate?

• Malate: magnesium bound to malic acid. It's well absorbed and often marketed for daytime energy, with little direct research behind that angle.
• Threonate: magnesium L-threonate is heavily marketed for the brain, but it carries very little magnesium per capsule and the human research is early.
• Taurate: magnesium bound to the amino acid taurine. It's interesting in animal studies, with limited human data.

None of these is a bad choice. They're less studied and usually cost more per milligram of magnesium.

Buffered vs non-buffered magnesium glycinate

This is the part that surprised me most. When I went looking for a glycinate to take every night, I couldn't believe how many "glycinate" bottles were padded with magnesium oxide.

"Buffered magnesium glycinate" usually means some glycinate plus a cheaper, denser form, most often oxide, so the brand can print a bigger number on fewer capsules. Non-buffered means all of the magnesium comes from glycinate. You can check a label in under a minute.

1. Find the "as" line. On the Supplement Facts panel, the words in parentheses after the magnesium amount name the source. "As magnesium bisglycinate" is one form. "As magnesium glycinate, magnesium oxide" is a blend.
2. Read "Other ingredients." Oxide, carbonate or a "magnesium blend" sometimes hides there instead.
3. Check the capsule count. If one small capsule claims 200mg or more of "glycinate," a denser form is almost certainly in the mix.

The full walkthrough, with a photo of our own panel, is in buffered vs non-buffered magnesium glycinate.

Elemental vs compound milligrams: why "200mg elemental" matters

A magnesium label can show two numbers. The compound weight is the magnesium plus its partner (glycine, citrate or oxygen). The elemental weight is the magnesium alone. Only the elemental number counts toward your daily intake, and it's the only fair way to compare brands. A bottle that says "1,000mg magnesium glycinate" may deliver only about 110 to 140mg of magnesium. "200mg elemental" tells you what you're actually getting.

Which magnesium for sleep, which for constipation, and can you take both?

For an evening routine

Most people who want magnesium as part of winding down pick glycinate, because it's gentle and won't send you to the bathroom at midnight. On the science: a 2023 systematic review found that higher magnesium status is linked with better sleep measures in observational studies, but the trials are few and mixed (Arab and colleagues, 2023). No trial has shown one form works better than another for sleep. Our guide to magnesium for sleep covers that research in more detail.

For occasional constipation

Citrate and oxide are the forms in over-the-counter laxatives, because they draw water into the bowel. If regularity is your main goal, talk to your clinician or pharmacist, since constipation that keeps coming back deserves a real look.

Taking both

Some people take glycinate at night and a little citrate for regularity. That's fine only if your total supplemental magnesium stays within the upper limit below, and I'd run it past your clinician first.

So which should you choose?

• Non-buffered glycinate if you want a daily magnesium that's gentle on your stomach and fits an evening routine.
• Citrate if you want a well-absorbed form and don't mind, or actually want, looser stools.
• Oxide if your clinician recommended it for a specific reason, or cost matters more to you than absorption.

How much magnesium is safe?

The NIH sets the Tolerable Upper Intake Level for magnesium from supplements and medicines at 350mg a day for adults. Magnesium from food doesn't count toward that limit. Adult women need 310 to 320mg a day in total from food and supplements, and 200mg of elemental magnesium sits under the upper limit with room for food. Talk to your clinician before starting any form if you have kidney disease, are pregnant or breastfeeding, or take osteoporosis medicines, certain antibiotics, diuretics or acid reducers, since magnesium can interact with them.

What we chose for NO. 04, and why

I wanted a magnesium I could hand a friend or my own mom without an asterisk. NO. 04 Magnesium Glycinate is 200mg of elemental magnesium from 1,700mg of Chelamax non-buffered magnesium bisglycinate in three capsules. There's no oxide. The only other ingredients are tapioca starch and the vegetable (HPMC) capsule, with 90 capsules to a bottle. Every lot is third-party tested, and the results are on our Certificate of Analysis page. It's $36 a bottle, or $30 with Subscribe and Save, and every number is also on our Rae Basics facts page. For timing, see when to take magnesium glycinate.

Quick answers

Sources

1. NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.
2. Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res. 2003;16(3):183-191.
3. Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr. 1990;9(1):48-55.
4. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001;14(4):257-262.
5. Schuette SA, Lashner BA, Janghorbani M. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. JPEN J Parenter Enteral Nutr. 1994;18(5):430-435.
6. Arab A, Rafie N, Amani R, Shirani F. The role of magnesium in sleep health: a systematic review of available literature. Biol Trace Elem Res. 2023;201(1):121-128.