Types of Magnesium Supplements: Which Form Should You Take?

Walk down a supplement aisle and you’ll see magnesium glycinate, citrate, oxide, malate, threonate, taurate, chloride and more, each promising something different. They all deliver the same mineral. What differs is the compound magnesium is attached to, which affects how much magnesium each pill contains, how well your body absorbs it, and how likely it is to upset your stomach.

This guide compares the main types of magnesium, explains what the research does and doesn’t show, and helps you match a form to your goal. For more buying guides, see our supplement guides, and to get magnesium from food first, see our guide to magnesium-rich foods.

Do you need a magnesium supplement?

Magnesium is involved in hundreds of chemical reactions in the body, including those that control muscle and nerve function, blood sugar, blood pressure, and making protein, bone and DNA. US survey data suggest that about half of Americans get less magnesium from food than they need, with older men and teenagers most likely to fall short.

Low intake doesn’t always mean deficiency, because healthy kidneys hold on to more magnesium when intake is low. True deficiency is more likely in people with digestive conditions such as Crohn’s or celiac disease, type 2 diabetes, long-term heavy drinking, and people taking certain medicines, including proton pump inhibitors for more than a year and some diuretics.

Food comes first. Pumpkin seeds, almonds, spinach, black beans, edamame, whole grains and dark chocolate are all good sources, and magnesium from food doesn’t count toward the upper limit. A supplement makes most sense if your diet is consistently low, you’re in one of the higher-risk groups, or your doctor has found low levels.

Elemental magnesium: the number that matters

Every magnesium supplement is a compound: magnesium bonded to something else, such as citric acid or the amino acid glycine. The “elemental” magnesium is the actual mineral in that compound. Some compounds are mostly magnesium; others are mostly the partner molecule.

On a US Supplement Facts panel, the amount listed is the elemental magnesium. “Magnesium (as magnesium glycinate) 200 mg” means 200 mg of magnesium. But the front of the bottle, or an ingredient list, may give the weight of the whole compound, such as “magnesium glycinate 1,000 mg”, which provides only about 140 mg of magnesium. Always use the Supplement Facts number. Our guide on how to read a supplement label explains this in more detail.

This is also why some forms need several large capsules a day: a form that’s only 8 to 14 percent magnesium takes a lot of powder to reach a meaningful dose.

Types of magnesium compared

Percentages are calculated from each compound’s chemical formula and vary with how a product is made, including how much water it contains. Absorption ratings are based on small studies; the NIH notes that forms that dissolve well in liquid, such as citrate, lactate, chloride and aspartate, are absorbed better than oxide and sulfate.

Each form in more detail

Magnesium glycinate

Magnesium bonded to glycine, an amino acid. It’s popular because it’s well tolerated and less likely to cause diarrhea than citrate or oxide, which makes it a good choice for daily use. It’s often marketed for sleep and anxiety because glycine has calming effects of its own, but there are no good trials showing glycinate works better than other forms for either. Look for “fully reacted” or “chelated” products, as some cheaper ones are mixed with magnesium oxide.

Magnesium citrate

One of the best-studied forms. It’s well absorbed and affordable, and it draws water into the bowel, so it has a mild laxative effect at higher doses. That’s a bonus if you tend toward constipation and a drawback if you don’t. Liquid magnesium citrate sold in pharmacies is a strong laxative and isn’t meant for daily supplementation.

Magnesium oxide

The most common form in cheap supplements and multivitamins, because it packs the most magnesium into a small tablet. However, much less of it is absorbed than with soluble forms. It’s effective as an osmotic laxative and antacid, and it’s the form used in many migraine studies, but it’s the most likely to cause loose stools.

Magnesium chloride and lactate

Both dissolve easily and are reasonably well absorbed. Chloride is found in some liquids, tablets and topical “magnesium oil” sprays. Lactate is gentle on the stomach and used in some slow-release tablets. Neither has a special benefit beyond providing magnesium.

Magnesium malate, taurate and L-threonate

These newer forms are sold for specific benefits: malate for energy and muscle pain, taurate for heart health, and L-threonate for memory, because animal studies suggest it raises magnesium in the brain. The evidence for these specific claims in people is limited, and threonate in particular is expensive and contains very little magnesium per capsule.

Magnesium sulfate (Epsom salt)

Taken by mouth, magnesium sulfate is a strong laxative and shouldn’t be used as a daily supplement. Epsom salt baths are relaxing, but there’s little evidence that meaningful amounts of magnesium are absorbed through the skin.

Which form for which goal?

Each finding below carries an evidence label, explained in our editorial policy.

Correcting low intake Strong evidence

Any well-absorbed form, such as glycinate, citrate, chloride or lactate, will raise magnesium intake. Choose the one that suits your stomach and budget.

Constipation Strong evidence

Magnesium oxide and citrate are established osmotic laxatives. A small trial in people with chronic constipation found magnesium oxide improved bowel movements compared with a placebo. Start low and take it with water. Don’t use laxative doses for more than a short time without advice.

Migraine prevention Moderate evidence

The American Academy of Neurology and the American Headache Society rate magnesium as “probably effective” for preventing migraine. Studies typically used 400 to 600 mg a day, often of magnesium oxide or citrate. These doses are above the upper limit, so use them only with your doctor’s guidance.

Blood pressure Moderate evidence

Magnesium supplements lower blood pressure slightly. A Cochrane review found an average drop of about 2 mmHg in diastolic pressure, which is small compared with medicine or cutting salt. The form doesn’t appear to matter much.

Sleep Limited evidence

Magnesium is one of the most popular sleep supplements, but the research is thin.

If you want to try it, glycinate is a reasonable choice because it’s gentle, but expect a modest effect at best. For other bedtime remedies, see our guide to valerian tea.

Muscle cramps Limited evidence

A 2020 Cochrane review found magnesium is unlikely to prevent ordinary muscle cramps in older adults. It might help cramps related to pregnancy, but the evidence there is mixed.

Anxiety, memory and energy Limited evidence

Claims for glycinate and anxiety, threonate and memory, and malate and energy rest mostly on animal studies, small trials or marketing. They haven’t been confirmed in good human trials.

How much to take and when

For general use, most adults take 100 to 350 mg of elemental magnesium a day from supplements. Starting at 100 to 200 mg lets you see how your stomach reacts. Remember that your diet already provides a few hundred milligrams.

• Timing: magnesium can be taken at any time of day. Many people take it in the evening, and taking it with food reduces stomach upset.
• Split doses: two smaller doses are often absorbed better and are less likely to cause diarrhea than one large dose.
• Counting totals: add up magnesium from your multivitamin, antacids, laxatives and any other products, as they all count toward the 350 mg limit.
• Separating from other minerals: very high doses of zinc can reduce magnesium absorption, so avoid taking large doses together.

Side effects, interactions and who should avoid it

The most common side effects are diarrhea, nausea and stomach cramps, especially with oxide, citrate and sulfate. Magnesium from food isn’t a concern for healthy people, because the kidneys remove any excess.

Very high doses, usually from large amounts of magnesium-containing laxatives or antacids, can cause magnesium toxicity, with low blood pressure, vomiting, muscle weakness, breathing problems and an irregular heartbeat. Deaths have been reported, mostly at doses over 5,000 mg a day.

See also our medical disclaimer.

How to choose a good product

• Check the elemental dose on the Supplement Facts panel, and how many capsules make one serving.
• Check the form: some “magnesium glycinate” products are buffered with cheaper magnesium oxide. Look for “100% chelated” or a breakdown of forms.
• Look for third-party testing: USP Verified, NSF or ConsumerLab seals confirm the product contains what it says and isn’t contaminated.
• Compare cost per 100 mg of magnesium, not per bottle. Low-percentage forms like threonate can cost several times more for the same amount.
• Skip big claims: products promising to cure anxiety, insomnia or high blood pressure are overselling.
• Choose a format you’ll use: capsules, tablets, powders and gummies all work. Gummies are often low in magnesium and contain sugar.

Magnesium FAQ