Magnesium Glycinate, Citrate, Oxide and More: Magnesium Forms Explained

By the nutrima editorial team · Last reviewed October 2026 · How we research and write

Short answer: Magnesium glycinate, citrate, oxide and the other "forms" on supplement labels are all magnesium bound to a different partner molecule (an amino acid, an organic acid or oxygen). The partner changes how much of the capsule's weight is actually magnesium and how well the compound dissolves. The NIH Office of Dietary Supplements (ODS) sets the adult RDA at 310–420 mg a day depending on age and sex, and a tolerable upper intake level of 350 mg a day for magnesium from supplements and medicines for anyone aged 9 and over. The number that matters on the Supplement Facts panel is elemental magnesium.

In this guide:

What magnesium is

Magnesium is an essential mineral: your body needs it but cannot make it, so it has to come from food, drinks or supplements. According to the NIH Office of Dietary Supplements, magnesium is a cofactor in more than 300 enzyme systems in the body, including those involved in protein synthesis, muscle and nerve function, and energy production. It is also a structural part of bone.

ODS notes that an adult body contains about 25 grams of magnesium, and that roughly 50–60% of it sits in the bones, with most of the rest in soft tissues.

Because magnesium is a reactive metal, it never appears in a supplement on its own. It is always part of a compound, a salt or a chelate, and the name of that compound is what you see on the label as the "form."

Magnesium forms compared

ODS lists magnesium oxide, citrate and chloride among the common forms in supplements, and notes that forms which dissolve well in liquid are more completely absorbed in the gut than less soluble forms. It also reports that small studies have found magnesium in the aspartate, citrate, lactate and chloride forms is absorbed more completely than magnesium oxide and magnesium sulfate. Other forms below are common on US shelves but are not individually compared in the ODS fact sheet.

The "approximate % magnesium by weight" column is simple chemistry: the share of the compound's molecular weight that is magnesium. Real ingredients vary with water content (hydrates) and with how a supplier makes them, so read these figures as rough guides and rely on the label for your product.

Form on the label What the compound is Approx. % magnesium by weight Notes
Magnesium oxide Magnesium bound to oxygen; a dense white mineral powder About 60% A lot of magnesium per gram of compound; ODS describes it as less soluble and less completely absorbed than citrate, lactate, aspartate or chloride in small studies
Magnesium citrate Magnesium bound to citric acid, the acid found in citrus fruit About 16% (anhydrous) Dissolves well in water; also used in some over-the-counter laxative products
Magnesium glycinate (bisglycinate) Magnesium chelated with two molecules of glycine, a small amino acid About 14% Bulky compound, so capsules carry less magnesium per gram; often "buffered" with other forms, which the label should name
Magnesium chloride Magnesium bound to chloride; a salt that readily absorbs water About 12% (hexahydrate) Used in liquids and flakes as well as tablets
Magnesium lactate Magnesium bound to lactic acid About 12% Listed by ODS among the more completely absorbed forms in small studies
Magnesium aspartate Magnesium bound to aspartic acid, an amino acid About 8% Listed by ODS among the more completely absorbed forms in small studies
Magnesium malate Magnesium bound to malic acid, the acid in apples About 15% Not individually reviewed in the ODS fact sheet
Magnesium taurate Magnesium bound to taurine, an amino sulfonic acid About 9% Not individually reviewed in the ODS fact sheet
Magnesium L-threonate Magnesium bound to threonic acid, a breakdown product of vitamin C About 8% Low magnesium per gram; not individually reviewed in the ODS fact sheet
Magnesium sulfate Magnesium bound to sulfate; the compound in Epsom salt About 10% (heptahydrate) ODS lists it with oxide as less completely absorbed in small studies
Magnesium carbonate Magnesium bound to carbonate; also used in antacids About 29% ODS lists carbonate among the forms most commonly reported to cause diarrhea

Two practical takeaways. First, a gram of magnesium glycinate and a gram of magnesium oxide contain very different amounts of magnesium, which is why capsule size alone tells you little. Second, being "more completely absorbed" in a small study is a statement about absorption, not about any health outcome. ODS does not rank one form as the right choice for everyone, and neither do we.

Combination products

Magnesium also appears inside multi-ingredient products, such as capsules that pair it with probiotics and enzymes, evening formulas that pair it with melatonin and chamomile (see our evening ingredients guide), and ketone salt products that list magnesium beta-hydroxybutyrate (BHB). In each case the Supplement Facts panel should still show the elemental magnesium per serving, which is what counts toward the upper limit.

What "elemental magnesium" on a label means

"Elemental magnesium" is the weight of the magnesium atoms alone, not the whole compound. ODS states that the Supplement Facts panel declares the amount of elemental magnesium in the product, not the weight of the entire magnesium-containing compound.

Here is how that plays out. Suppose a capsule holds 1,000 mg of magnesium glycinate. At about 14% magnesium by weight, that is roughly 140 mg of elemental magnesium. The same 1,000 mg of magnesium oxide would hold roughly 600 mg of elemental magnesium. The Supplement Facts row for magnesium should show the elemental figure (140 mg or 600 mg in this example), often followed by the form in parentheses, for example "Magnesium (as magnesium glycinate) 140 mg."

Some product names and front labels quote the compound weight instead, so the big number on the front and the number on the Supplement Facts panel can differ. When they do, the Supplement Facts panel is the figure to compare against the RDA and the upper limit. If a front label is unclear, the panel is the tiebreaker, and our store's Supplement Facts label guide walks through every row.

How much magnesium: RDA and upper limit

The Recommended Dietary Allowance (RDA) is the average daily intake that meets the needs of nearly all healthy people in a group. It covers magnesium from all sources: food, drinks and supplements combined. These figures are from the ODS health professional fact sheet.

Age Male Female Pregnancy Lactation
Birth to 6 months 30 mg* 30 mg*
7–12 months 75 mg* 75 mg*
1–3 years 80 mg 80 mg
4–8 years 130 mg 130 mg
9–13 years 240 mg 240 mg
14–18 years 410 mg 360 mg 400 mg 360 mg
19–30 years 400 mg 310 mg 350 mg 310 mg
31–50 years 420 mg 320 mg 360 mg 320 mg
51+ years 420 mg 320 mg

*Adequate Intake (AI), used for infants where there is not enough data to set an RDA.

The 350 mg upper limit applies to supplements, not food

The Tolerable Upper Intake Level (UL) is the most you can take daily without likely risk of side effects. For magnesium, ODS explains that the UL applies only to magnesium from dietary supplements and medicines, not to magnesium naturally present in food and drinks, because the kidneys remove excess dietary magnesium in healthy people.

Age UL for supplemental magnesium
Birth to 12 months Not established
1–3 years 65 mg
4–8 years 110 mg
9 years and older (including pregnancy and lactation) 350 mg

Note that the UL for adults (350 mg) is lower than the adult RDA (310–420 mg). That is not a contradiction: the RDA counts food, and the UL counts only supplements and medicines. Antacids and laxatives that contain magnesium also count toward the 350 mg, so add those up alongside any supplement.

% Daily Value

The % Daily Value (%DV) on a Supplement Facts panel compares the amount per serving with a single reference number set by the FDA. For magnesium, the Daily Value for adults and children 4 years and older is 420 mg. A product with 210 mg of elemental magnesium per serving would therefore show 50% DV.

Magnesium in food

ODS lists legumes, nuts, seeds, whole grains and green leafy vegetables such as spinach among good food sources, along with fortified breakfast cereals and other fortified foods. Milk, yogurt and some other dairy products contain magnesium too, and tap, mineral and bottled water can supply some, depending on the source. ODS notes that many people in the United States take in less magnesium than recommended from food alone.

How to read a magnesium label

  1. Find the serving size. "Serving size: 2 capsules" means every number on the panel is for two capsules, not one.
  2. Read the elemental amount. The magnesium row shows the elemental magnesium in milligrams (mg) per serving. Compare this number, not the compound weight, with the UL of 350 mg.
  3. Check the form in parentheses. "(as magnesium bisglycinate chelate)" or "(as magnesium oxide, magnesium citrate)" tells you which compounds are used. A list of several forms means a blend.
  4. Look at %DV. Based on 420 mg for adults.
  5. Scan for other magnesium sources. Multivitamins, electrolyte drinks, ketone salts, antacids and laxatives may also contain magnesium.
  6. Read "Other ingredients." This lists the capsule shell, fillers and flow agents, which matters if you avoid gelatin or certain allergens.
  7. Check for a "proprietary blend." If magnesium is inside a blend, the label may show only the total blend weight. In that case you may not be able to tell the exact magnesium amount from the panel; ask the seller or contact the manufacturer.

Who should check with a doctor first

Talk to your doctor or pharmacist before taking a magnesium supplement if any of these apply to you:

  • Kidney disease or reduced kidney function. ODS explains that the risk of magnesium toxicity rises with impaired kidney function or kidney failure, because the kidneys lose the ability to remove excess magnesium.
  • You take prescription or regular over-the-counter medicines, especially those in the interactions list below.
  • Pregnancy or breastfeeding. Needs differ (see the RDA table), and the 350 mg UL still applies.
  • Under 18. Children's ULs are much lower (65 mg at ages 1–3, 110 mg at ages 4–8). Do not give adult products to children without a clinician's advice.
  • Digestive conditions, type 2 diabetes, long-term heavy alcohol use, or older age. ODS lists these groups as more likely to have low magnesium status, so a clinician may want to look at your situation rather than you guessing at a dose.
  • Any heart condition or scheduled surgery. Tell your care team about every supplement you take.

ODS notes that high intakes of magnesium from supplements or medicines can cause diarrhea, nausea and abdominal cramping, and that magnesium carbonate, chloride, gluconate and oxide are the forms most commonly reported to cause diarrhea. Very large doses of magnesium-containing laxatives and antacids (more than 5,000 mg a day) have been linked to magnesium toxicity, which ODS describes as including low blood pressure, nausea, vomiting, facial flushing, muscle weakness and irregular heartbeat. If you notice symptoms like these, stop and seek medical help.

Medication interactions listed by ODS

The ODS health professional fact sheet lists these interactions. This is a summary, not a complete list; your pharmacist can check your exact medicines.

Medication type Examples What ODS says
Bisphosphonates (bone medicines) Alendronate Magnesium-rich supplements or medicines can decrease absorption of oral bisphosphonates; ODS advises separating them by at least 2 hours.
Some antibiotics Tetracyclines (such as doxycycline) and quinolones (such as ciprofloxacin) Magnesium can form insoluble complexes with these antibiotics. ODS advises taking the antibiotic at least 2 hours before or 4–6 hours after a magnesium-containing supplement.
Loop and thiazide diuretics Furosemide, hydrochlorothiazide Can increase the loss of magnesium in urine.
Potassium-sparing diuretics Amiloride, spironolactone Reduce magnesium excretion.
Proton pump inhibitors (PPIs) Esomeprazole, lansoprazole Taken for prolonged periods (typically more than a year), can cause low blood magnesium.

ODS also notes that very high doses of zinc from supplements can interfere with magnesium absorption.

Storage

Keep magnesium products in the original container with the lid tightly closed, in a cool, dry place away from direct sunlight. Some forms, especially magnesium chloride, attract moisture, so avoid bathrooms and steamy kitchens. Keep all supplements out of children's reach, given the much lower children's ULs. Check the date printed on the bottle before use.

Shop this category

Magnesium products and products that list magnesium are in our Daily Essentials collection, with more in Capsules. Each product page shows the full Supplement Facts panel, including the elemental amount, the form and the country of manufacture.

Related reading: our evening ingredients guide covers melatonin, L-theanine and botanicals that often appear next to magnesium, and the focus ingredients guide covers bacopa, alpha-GPC and caffeine. All our guides are collected on the guides hub.

Frequently asked questions

Is magnesium glycinate the same as magnesium bisglycinate?

In practice, the two names are used for the same idea: magnesium chelated with glycine. "Bisglycinate" spells out that two glycine molecules are bound to each magnesium atom. Some products are "buffered," meaning another form such as magnesium oxide is mixed in; the label's parentheses should list every form used.

Why does my magnesium glycinate capsule have less magnesium than an oxide tablet?

Glycine is a relatively large partner molecule, so only about 14% of magnesium glycinate's weight is magnesium, compared with about 60% for magnesium oxide. A capsule can only hold so much powder, which is why glycinate products often list a lower elemental amount per capsule or use a multi-capsule serving.

Does the 350 mg limit include magnesium from food?

No. ODS sets the 350 mg UL for magnesium from supplements and medicines only. Magnesium naturally present in food and drinks does not count toward it.

Which magnesium form is absorbed most completely?

ODS reports that forms that dissolve well in liquid are more completely absorbed, and that small studies found the aspartate, citrate, lactate and chloride forms absorbed more completely than oxide and sulfate. ODS does not name a single form as the right one for everyone; a doctor or pharmacist can help if you have a specific reason to choose.

Can I take magnesium with my antibiotic?

For tetracycline and quinolone antibiotics, ODS advises taking the antibiotic at least 2 hours before or 4–6 hours after a magnesium-containing supplement. Ask your pharmacist about your specific prescription.

Is it safe to take magnesium if I have kidney disease?

Do not start magnesium without your doctor's approval. ODS explains that impaired kidney function raises the risk of magnesium building up to toxic levels.

What does "% Daily Value" mean for magnesium?

It is the amount per serving compared with the FDA's Daily Value of 420 mg for adults and children 4 years and older. It is a labeling reference, not a personal target.

Sources

These statements have not been evaluated by the Food and Drug Administration. This product information is not intended to diagnose, treat, cure, or prevent any disease. Talk to your doctor before starting any supplement.