Magnesium Forms Compared: Glycinate, Citrate, Oxide, Malate, Threonate and More
Magnesium glycinate, citrate, oxide, malate, threonate and other forms compared: what small human studies, animal work and a laxative trial show, and what is missing.
Content last updated . This page has not been medically reviewed.
The question
"Which magnesium is best?" has no single answer, because it depends on what a person wants it for, and the documented differences are small and mostly about absorption. For absorption into the blood, small human studies found citrate better than oxide. For the other forms, evidence is thin, comes from special groups or animals, or is missing. Marketing claims for specific benefits (sleep, calm, memory) mostly outrun the form-by-form evidence. For roles, food sources and safety, see Magnesium.The forms side by side
| Form | What is documented | Evidence strength | Caution |
|---|---|---|---|
| Citrate | In 46 healthy adults given 300 mg of elemental magnesium daily for 60 days, citrate gave the highest serum magnesium. [1] In 14 healthy men (400 mg, single dose), it showed higher bioavailability than oxide. [2] | Small human trials, biomarker | Absorption is not the same as benefit. |
| Oxide | Showed no differences compared with placebo in the 46-person trial. [1] Used at 1.5 g as a laxative, it improved chronic constipation symptoms in 68.3% versus 11.7% on placebo. [3] | Small trials; laxative use is a separate question | Loosens stools at higher amounts. |
| Glycinate (diglycinate) | In 12 people who had part of the small bowel removed, absorption overall was not different from oxide (23.5% vs 22.8%), and it was better tolerated. [4] | Special population, not healthy adults | Cannot be applied to healthy adults. |
| Amino-acid chelate | Organic forms (citrate and an amino-acid chelate) showed greater absorption than oxide at 60 days by urinary excretion. [1] | Small trial | Chelate type in that trial is not named as glycinate. |
| Malate, acetyl taurate | In mice, brain magnesium levels rose with acetyl taurate; malate was also tested, and the abstract reports no malate-specific result. [5] | Preclinical | Animal results do not transfer. |
| Threonate | A 30-day trial in 109 healthy Chinese adults tested a formula based on magnesium L-threonate and phosphatidylserine, with vitamins C and D. [6] | Promising but limited | The formula was tested against placebo, not against other magnesium forms. |
| Chloride; malate in humans | Proper evidence not found in the sources we read for human trials comparing these with other forms. | Insufficient evidence | Do not infer benefit from marketing. |
Reading the table carefully
- Absorption is not the same as benefit. The trials measure blood or urine magnesium, not sleep, cramps or mood. Biomarker change is not a clinical outcome. [2]
- Threonate studies. The 109-person trial tested a formula that also contained phosphatidylserine and vitamins C and D, so an effect cannot be attributed to magnesium threonate alone. [6] A second 12-week trial (44 older adults with cognitive impairment, 23 on the test product) used a proprietary formula whose abstract does not name its ingredients; its PubMed keywords include magnesium and L-threonate. [7] Neither compared threonate with citrate or glycinate.
- Animal results do not transfer. The mouse work gave magnesium compounds by mouth to mice and measured tissue levels. [5]
- Special groups. The glycinate result comes from people with small-bowel resection. [4]
Official amounts and tolerability (UK, NHS)
The NHS says more than 400 mg of magnesium for a short time can cause diarrhoea, and that 400 mg or less a day from supplements is unlikely to cause harm. [8] UK reference amounts for adults aged 19 to 64 are 300 mg a day for men and 270 mg for women. [8] Other countries use different figures. We could not read the US NIH Office of Dietary Supplements page (access blocked), so we quote no US figures; see RDA, AI, DV and UL. Check whether a label states elemental magnesium, since studies report amounts that way. [1]No universal winner
Citrate has the best human absorption data against oxide; oxide is documented as a laxative; glycinate and threonate have little form-versus-form evidence in healthy adults. A clinician or pharmacist can help match a form to a person.Frequently asked questions
Which is better, magnesium glycinate or citrate?
Proper evidence not found for a head-to-head trial in healthy adults. Citrate has the better human absorption data against oxide. [1][2] Glycinate was well tolerated in a small trial of people with poor absorption. [4]
Is magnesium oxide bad?
It absorbed less than citrate in the studies above, and it works as a laxative at higher amounts. [1][3] That is a documented difference, not a reason to avoid or choose it.
Is magnesium threonate better for the brain?
Two small trials of formulas linked to threonate reported cognitive gains over placebo, but they used proprietary formulas and no other magnesium form for comparison. [6][7] Evidence is promising but limited.
How much magnesium is too much from supplements?
The NHS says 400 mg or less a day from supplements is unlikely to cause harm. [8]
Is magnesium malate or chloride better absorbed?
Proper evidence not found in the sources we read for human absorption trials of these forms. We looked at the PubMed records listed on this page.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: evidence in adequately nourished people, promising but limited, preclinical (animals or cells), insufficient evidence.
Safety and who should ask a clinician
- Kidney conditions. If your kidneys do not work well, ask a clinician before taking any magnesium supplement; see Minerals, supplements and kidney disease.
- Medicines. Ask a pharmacist whether magnesium needs spacing from your medicines; see Spacing supplements and medicines and How interactions work.
- Pregnancy, children, liver, surgery. Proper evidence not found in the sources we read for form-specific advice. Ask a clinician, and tell the surgical team about supplements: Supplements before surgery.
- Magnesium for sleep is covered in Magnesium for sleep; this page does not repeat it.
References
- Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res, 2003 Read 2026-10-23.
- Assessment of bioavailability of Mg from Mg citrate and Mg oxide by measuring urinary excretion in Mg-saturated subjects. Magnes Res, 2019 Read 2026-10-23.
- Senna Versus Magnesium Oxide for the Treatment of Chronic Constipation. Am J Gastroenterol, 2021 Read 2026-10-23.
- Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. JPEN, 1994 Read 2026-10-23.
- Dose-Dependent Absorption Profile of Different Magnesium Compounds. Biol Trace Elem Res, 2019 (mouse study) Read 2026-10-23.
- A Magtein, Magnesium L-Threonate, -Based Formula Improves Brain Cognitive Functions in Healthy Chinese Adults. Nutrients, 2022 Read 2026-10-23.
- Efficacy and Safety of MMFS-01, a Synapse Density Enhancer, for Treating Cognitive Impairment in Older Adults. J Alzheimers Dis, 2016 Read 2026-10-23.
- NHS, Other vitamins and minerals (UK). Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.