Medically reviewed by Dr. Reina Punj, MBBS, PG Diploma in Endocrinology (University of South Wales), Lead Physician, Excelgenics Clinical Panel.
Magnesium glycinate and magnesium citrate are both organic forms that the body absorbs better than magnesium oxide. Citrate has the stronger direct absorption evidence and is also used, in larger doses, as a laxative, so it is more likely to loosen stools. Glycinate (the same thing as bisglycinate) is often chosen because many people find it gentle on the stomach, but no trial has shown it to be better absorbed than citrate. For most healthy adults, either is a reasonable choice; your stomach, budget and the elemental magnesium per tablet matter more than the name.
This guide compares magnesium glycinate vs citrate, and also how glycinate compares with magnesium oxide and magnesium L-threonate. For dosage, timing and safety in more depth, see our Magnesium Supplements Guide.
Magnesium glycinate vs citrate vs oxide vs threonate: at a glance
| Feature | Glycinate (bisglycinate) | Citrate | Oxide | L-threonate |
|---|---|---|---|---|
| What it is | Magnesium bound to the amino acid glycine | Magnesium bound to citric acid | A simple inorganic salt | Magnesium bound to threonic acid |
| Absorption evidence | Better than oxide in some small studies; not shown to beat citrate | Better than oxide in several small human studies | Lowest of the common forms (about 4% in one small study) | Very limited human data |
| Effect on stools | Loose stools possible, but many find it gentle | More likely to loosen stools; also sold as a laxative | Often loosens stools | Few data |
| Usually chosen for | Daily, long-term use; evening routines | General top-up; occasional constipation | Low cost | Marketed for brain health |
Is magnesium glycinate the same as bisglycinate?
Yes. Magnesium bisglycinate, magnesium glycinate and magnesium diglycinate are names for the same compound: one magnesium atom held by two glycine molecules. "Bis" just means two. When a label says bisglycinate and a search result says glycinate, they mean the same ingredient. We explain the label terms, including "buffered" and "fully reacted", in Magnesium Glycinate vs Bisglycinate.
Magnesium glycinate vs citrate: what the research shows
Absorption research on magnesium forms is small and mostly short term. The main findings:
- Walker and colleagues (2003) gave 46 healthy adults 300 mg of elemental magnesium a day for 60 days as citrate, an amino acid chelate or oxide, or a placebo. Both citrate and the chelate raised urinary magnesium more than oxide, a sign of better absorption. Citrate gave the highest blood and saliva levels, and the authors concluded it was the most bioavailable form in their study. The abstract describes the chelate only as an "amino acid chelate", not specifically glycinate.
- A 2021 systematic review (Pardo and colleagues, 14 studies) concluded that organic forms appear more bioavailable than inorganic ones, that absorption also depends on the dose, and that all forms may maintain normal levels in healthy people without a prior shortfall.
- We found no published head-to-head trial comparing glycinate with citrate for absorption or stomach comfort.
So the honest answer to "magnesium citrate vs glycinate: which is better absorbed?" is that both are well absorbed, citrate has more direct evidence, and the difference between them in daily use is not established.
Magnesium citrate vs glycinate for your stomach
Unabsorbed magnesium draws water into the bowel. Magnesium citrate is sold in larger doses as a saline laxative for occasional constipation and to empty the bowel before a colonoscopy (MedlinePlus), which is why it is the form more associated with loose stools. At ordinary supplement doses many people take citrate without trouble, but if your stomach is sensitive, this is the main practical difference.
Glycinate has a reputation for being gentle. It is generally well tolerated, though loose stools, nausea and stomach cramps can still happen with any magnesium supplement, especially at higher doses. The NIH lists carbonate, chloride, gluconate and oxide as the forms most often reported to cause diarrhoea.
Magnesium glycinate vs magnesium oxide
Magnesium oxide packs a lot of magnesium into a small tablet (it is about 60% magnesium by weight), which keeps it cheap. The catch is absorption:
- In normal volunteers, Firoz and Graber (2001) measured fractional absorption of only about 4% from magnesium oxide, while chloride, lactate and aspartate forms were absorbed significantly better.
- Lindberg and colleagues (1990) found oxide almost insoluble in water, and urinary magnesium rose far more after citrate than after oxide.
- In a small crossover trial of 12 patients with part of the small intestine removed, magnesium diglycinate and oxide were absorbed similarly overall (about 23% each). In the four patients who absorbed oxide worst, glycinate was absorbed better, and patients tolerated glycinate better (Schuette and colleagues, 1994).
For a daily top-up, glycinate or citrate is usually the better choice than oxide. Oxide is also used as an antacid and, short term, as a laxative (MedlinePlus).
Magnesium glycinate vs magnesium threonate
Magnesium L-threonate was developed after a 2010 study in rats (Slutsky and colleagues, Neuron) found it raised magnesium levels in the brain. Human evidence is thin. The main trial randomised 51 adults aged 50–70 with self-reported memory complaints to a threonate-based product or placebo for 12 weeks; 44 completed it. The product group scored better on cognitive tests, but sleep and anxiety improved in both groups. The study was funded by the company that developed the ingredient, which also analysed the cognitive results (Liu and colleagues, 2016).
As with any form, check the elemental magnesium per serving on the label. If your aim is simply to meet your daily magnesium needs, glycinate or citrate is the more practical choice; threonate is a specialist product with early-stage evidence.
Which should you choose?
- Sensitive stomach, daily long-term use: glycinate (bisglycinate) is a sensible first choice.
- Most direct absorption evidence: citrate, if loose stools are not a problem for you.
- Occasional constipation: citrate or oxide may be suggested by your doctor or pharmacist, but do not use magnesium as a regular laxative without advice.
- Brain-health claims: threonate's human evidence is limited; treat marketing claims with caution.
Whatever the form, compare products on elemental magnesium per serving, not the compound weight. The NIH upper limit for magnesium from supplements is 350 mg a day for adults (food does not count). For example, Magneva Magnesium Bisglycinate 350mg + Vitamin B6 provides 350 mg of elemental magnesium per vegan tablet, the full limit, so it should not be combined with other magnesium supplements. For timing and dose, see Magnesium Glycinate Dosage and Best Time to Take It, and if you would rather start with food, see Magnesium Rich Foods.
Safety
Common side effects of magnesium supplements are loose stools, nausea and stomach cramps. Take magnesium only on medical advice if you have kidney disease, and speak to your doctor if you are pregnant or breastfeeding. Take tetracycline or quinolone antibiotics at least 2 hours before or 4–6 hours after magnesium, and separate bisphosphonates from magnesium by at least 2 hours. More detail is in Magnesium Glycinate Side Effects.
Frequently asked questions
Is magnesium glycinate or citrate better?
Neither is better for everyone. Citrate has more direct absorption evidence but is more likely to loosen stools; glycinate is often better tolerated. Both are better absorbed than oxide.
Which is better for sleep, glycinate or citrate?
No study has compared the two forms for sleep. Research on magnesium and sleep in general is limited: a 2021 review of three small trials in older adults rated the evidence as low to very low quality. Magnesium contributes to normal functioning of the nervous system and to normal psychological function, and is better seen as one part of a healthy routine.
Can I take magnesium glycinate and citrate together?
You can, but add up the elemental magnesium from both and keep the total from supplements within 350 mg a day unless your doctor advises otherwise.
Which magnesium is used for constipation?
Citrate and oxide have the stronger laxative effect. Persistent constipation should be checked by a doctor rather than self-treated long term.
References
- Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research. 2003;16(3):183–191. PubMed 14596323
- Pardo MR, Garicano Vilar E, San Mauro Martín I, Camina Martín MA. Bioavailability of magnesium food supplements: a systematic review. Nutrition. 2021;89:111294. doi:10.1016/j.nut.2021.111294
- Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research. 2001;14(4):257–262. PubMed 11794633
- Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. Magnesium bioavailability from magnesium citrate and magnesium oxide. Journal of the American College of Nutrition. 1990;9(1):48–55. doi:10.1080/07315724.1990.10720349
- Schuette SA, Lashner BA, Janghorbani M. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. Journal of Parenteral and Enteral Nutrition. 1994;18(5):430–435. doi:10.1177/0148607194018005430
- Slutsky I, Abumaria N, Wu LJ, et al. Enhancement of learning and memory by elevating brain magnesium. Neuron. 2010;65(2):165–177. doi:10.1016/j.neuron.2009.12.026
- Liu G, Weinger JG, Lu ZL, Xue F, Sadeghpour S. Efficacy and safety of MMFS-01, a synapse density enhancer, for treating cognitive impairment in older adults: a randomized, double-blind, placebo-controlled trial. Journal of Alzheimer's Disease. 2016;49(4):971–990. doi:10.3233/JAD-150538
- Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies. 2021;21:125. doi:10.1186/s12906-021-03297-z
- MedlinePlus. Magnesium citrate. US National Library of Medicine. medlineplus.gov
- MedlinePlus. Magnesium oxide. US National Library of Medicine. medlineplus.gov
- National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. ods.od.nih.gov
This article is for general education and is not medical advice. Food supplements are not intended to diagnose, treat, cure or prevent any disease. Consult a qualified healthcare professional before starting any supplement, particularly if you are pregnant, breastfeeding, have a medical condition or take medication.
