Magnesium Glycinate vs Citrate vs Oxide: Which Is Best for Absorption?
Published Updated Ben Law
Reviewed by Sarah Law, Naturopathic Nutritionist
- Best for everyday use: glycinate. Well absorbed and the gentlest form on digestion, which makes it the easiest to take every day, including in the evening.
- Citrate has the strongest head-to-head absorption data, but it is mildly laxative, so it suits digestion and daytime use.
- Oxide is high in elemental magnesium but poorly absorbed (around 4% fractional absorption in a human study).
- Our pick: a fully reacted Magnesium Glycinate, 303 mg elemental magnesium per serving, Eurofins tested, about 63p a day.
Magnesium glycinate vs citrate: for everyday use, choose glycinate. Both absorb far better than magnesium oxide, but glycinate is the gentlest form on digestion, while citrate can act as a mild laxative. Citrate actually has the strongest head-to-head absorption data; glycinate's advantage is that you can take it every day without your gut noticing. Oxide holds the most magnesium per gram, yet only around 4% was absorbed in human testing, so skip it for ongoing supplementation. Whichever well-absorbed form you pick, magnesium contributes to normal muscle function, normal psychological function and the reduction of tiredness and fatigue.
The glycinate figures in this comparison come from our own label and lab report. Love Life Supplements Magnesium Glycinate is a fully reacted, non-buffered bisglycinate: 2,750 mg of magnesium bisglycinate gives 303 mg elemental magnesium per four-capsule serving, which is 11% elemental, under the 14.1% ceiling for pure bisglycinate, so there is no hidden oxide. Eurofins confirmed the magnesium content in July 2026 (report AR-733-2026-00087324-03). A 240-capsule tub is a 60-day supply at £37.95, about 63p a day (57p on a first subscription order), or $51.18 on our US store, about 85 cents a day, rated 4.8 out of 5 from 295 customer ratings, and each tub is covered by a 60-day money-back guarantee.
Magnesium Citrate vs Glycinate vs Oxide: The Comparison at a Glance
Magnesium glycinate vs citrate vs oxide, in one line each: choose glycinate for daily, long-term supplementation and evening routines. Choose citrate for daytime use if its mild laxative effect suits you. Skip oxide for ongoing supplementation: with around 4% absorption, most of the dose never reaches your cells [1].
| Form | Absorption | Best for | Watch-outs |
|---|---|---|---|
|
Glycinate (bisglycinate) |
High, gentle | Daily use, evening routines, sensitive stomachs | Larger dose volume (capsules), as it is only 11 to 14% magnesium |
| Citrate | Good (strongest head-to-head data) | Digestion, occasional constipation, daytime | Can be mildly laxative |
| Oxide | Low (~4%) | Short-term constipation relief only | Poorly absorbed; bloating, loose stools |
Over the years I have tested nearly every form of magnesium, some worked brilliantly, others caused discomfort. That is why we use a fully reacted magnesium bisglycinate in our Magnesium Glycinate Capsules: gentle on the gut, well absorbed, and the one I take every night. It is pure, filler-free and third-party tested, made in UK GMP and BRC-certified facilities.
Magnesium Glycinate vs Citrate: Which Should You Choose?
Choose magnesium glycinate if you want a daily supplement that will not upset your stomach; choose magnesium citrate if you also want a gentle laxative effect, or you take it during the day and tolerate it well. On absorption alone the two are close, and citrate has slightly stronger published data [3][4]. The deciding factor for most people is tolerance, so magnesium citrate vs magnesium glycinate really comes down to how your gut responds.
- Absorption: in a 60-day randomised trial of 46 healthy adults, citrate produced the highest serum magnesium of the forms tested, and both citrate and an amino-acid chelate (the family glycinate belongs to) were absorbed better than oxide [4].
- Gut comfort: citrate is soluble and osmotically active, so higher doses can loosen stools. Glycinate appears to be absorbed partly intact through a dipeptide pathway and was better tolerated than oxide by every patient in one trial [5].
- Dose per capsule: citrate is around 16% magnesium, glycinate 11 to 14%, so glycinate needs a slightly larger capsule load for the same elemental dose.
- Timing: glycinate is the usual evening choice; citrate is usually taken earlier in the day, when a laxative effect is less inconvenient.
The difference between magnesium citrate and magnesium glycinate, in short, is the carrier: citric acid versus the amino acid glycine. That carrier decides how the magnesium behaves in your gut more than how much of it you absorb. In the UK, both forms are sold widely; check the label for the elemental figure, not the compound weight.
Magnesium Oxide vs Glycinate: Which Is Better?
Magnesium glycinate vs magnesium oxide: glycinate is better for supplementation. Magnesium oxide is about 60% magnesium by weight, so a small tablet carries a big number on the label, which is why the magnesium glycinate vs oxide comparison is so often misread, but it is poorly soluble and only around 4% was absorbed in a human study of commercial preparations [1]. In a 60-day trial, oxide made no measurable difference compared with placebo [4].
Glycinate carries less magnesium per gram but much more of it is usable, and it is far less likely to cause the loose stools that oxide is known for [2]. The one fair point for oxide comes from a small isotope study in patients with ileal resection, where overall absorption from glycinate (diglycinate) and oxide was similar, 23.5% vs 22.8%. Even there, glycinate absorbed twice as well in the four patients who absorbed oxide worst (23.5% vs 11.8%) and was better tolerated by all of them [5]. Oxide's real use is short-term constipation relief, not daily top-up. The same logic answers magnesium citrate vs oxide: citrate is far more soluble and produced a much larger rise in urinary magnesium after an equal dose [3].
Magnesium Glycinate (Bisglycinate)
Magnesium glycinate binds magnesium to the amino acid glycine, creating a chelated compound that is well absorbed and gentle on digestion. Part of it appears to be absorbed intact as a dipeptide in the small intestine [5], which may explain why it rarely causes a laxative effect. Magnesium bisglycinate and magnesium glycinate are the same thing on most labels: magnesium bound to two glycine molecules. It is the go-to form for daily use without digestive discomfort, and the focus of this guide.
Magnesium Citrate
Magnesium citrate is magnesium combined with citric acid. It is highly soluble even in water [3], absorbs well and gently stimulates the bowel, which can help with occasional constipation. That same effect makes it less suitable for people with a sensitive gut, so many people take it during the day or after exercise rather than as a nightly routine.
Magnesium Oxide
Magnesium oxide contains a high percentage of elemental magnesium, but its absorption is very low, with one well-known analysis putting fractional absorption around 4% [1]. It is virtually insoluble in water and only 43% soluble even in simulated peak stomach acid [3]. Much of it passes through the gut unused and can draw water into the intestines, causing loose stools; oxide is one of the forms most commonly reported to cause diarrhoea [2]. It is cheap and common in generic tablets, but not ideal for ongoing supplementation.
What Is the Difference Between Magnesium Citrate, Glycinate and Oxide?
The difference is the carrier molecule and how much magnesium survives digestion. Oxide is magnesium bound to oxygen: dense, about 60% elemental, but poorly soluble, with roughly 4% fractional absorption in human testing. Citrate binds magnesium to citric acid: around 16% elemental and well absorbed. Glycinate binds it to the amino acid glycine: 11 to 14% elemental, well absorbed, and the least likely to cause a laxative effect.
- Glycinate: well absorbed and the most tolerable, the best choice for consistent daily supplementation.
- Citrate: good absorption, suitable for occasional use or digestive support.
- Oxide: low uptake and poor solubility, better avoided for long-term use.
| Form | Elemental magnesium content | Compound needed for 300 mg elemental | Absorption evidence |
|---|---|---|---|
| Magnesium oxide | ~60% (highest density) | ~500 mg | ~4% fractional absorption in a human study of commercial preparations [1]; no different from placebo after 60 days [4] |
| Magnesium citrate | ~16% | ~1,900 mg | More soluble and better absorbed than oxide [3]; highest serum magnesium in a 60-day trial [4] |
| Magnesium glycinate (fully reacted bisglycinate) | Up to 14.1% when genuinely non-buffered | ~2,100 mg or more | Amino-acid chelate absorbed better than oxide at 60 days [4]; absorbed partly intact and best tolerated [5] |
| Love Life Supplements Magnesium Glycinate | 11% elemental: about 76 mg per capsule, 303 mg per 4-capsule serving | 2,750 mg per serving | Fully reacted, non-buffered; magnesium content confirmed by Eurofins (measured twice, both within uncertainty of the 303 mg label); 63p a day (£37.95, 240 capsules, 60 servings) |
Elemental percentages reflect the chemistry of each form (bisglycinate's theoretical maximum is 14.1%); compound amounts are our calculation for 300 mg elemental magnesium. Love Life Supplements figures are label values and the July 2026 Eurofins report, with the price checked 13 October 2026.
"In practice the form matters as much as the dose. I steer most clients toward glycinate for daily use because it absorbs well and rarely upsets digestion. I keep citrate for short-term constipation or daytime use, and I rarely recommend oxide for anything beyond occasional bowel relief."
Sarah Law, Naturopathic Nutritionist & Functional Practitioner
What Do the Absorption Studies Actually Show?
The studies agree on one thing: oxide is the worst absorbed. Citrate has the most consistent head-to-head wins, and glycinate's evidence is thinner than many brands imply, with its clearest advantage being tolerability. Here is every human study this guide relies on, in one place.
| Study | Who and how | Forms compared | What it found |
|---|---|---|---|
| Lindberg et al., 1990 [3] | Healthy volunteers; urinary magnesium after a single 25 mmol dose, plus lab solubility tests | Citrate vs oxide | Citrate was far more soluble (55% in water vs virtually insoluble oxide) and raised urinary magnesium significantly more |
| Firoz & Graber, 2001 [1] | Healthy volunteers; urinary magnesium on about 21 mEq a day | Oxide, chloride, lactate, aspartate | Oxide fractional absorption about 4%; the other three significantly higher and equivalent to each other |
| Walker et al., 2003 [4] | 46 healthy adults; randomised, double-blind, placebo-controlled, 60 days | Citrate, amino-acid chelate, oxide | Citrate and chelate absorbed better than oxide; citrate gave the highest serum magnesium; oxide no different from placebo |
| Schuette et al., 1994 [5] | 12 patients after ileal resection; double-blind crossover with an isotope tracer | Diglycinate vs oxide | Overall absorption 23.5% vs 22.8%; 23.5% vs 11.8% in the four poorest absorbers; diglycinate better tolerated by all patients |
| Pajuelo et al., 2024 [6] | 40 adults on a low-magnesium diet; crossover, single fasted dose, 6 hours of blood tests; industry funded | Microencapsulated form vs oxide, citrate, bisglycinate | Plasma magnesium rose after oxide (at 1 hour) and citrate (at 4 hours) but not significantly after bisglycinate in the 6-hour window |
Two points matter when you read this. First, single-dose studies measured over a few hours tell you how fast a form shows up in blood or urine, not how well it tops up the body's stores over weeks; the 60-day trial is the more relevant design for daily use, and there oxide did no better than placebo [4]. Second, less than 1% of the body's magnesium is in blood serum [2], so blood tests are a blunt measure. For a daily supplement, what you can tolerate and keep taking matters as much as any absorption figure, which is why glycinate remains our recommendation.
Dosage and How to Take
The NHS says adults aged 19 to 64 need 300 mg (men) or 270 mg (women) of magnesium a day in total, and that 400 mg or less a day from supplements is unlikely to cause any harm [7]. In the US, the NIH Recommended Dietary Allowance is 400 to 420 mg for men and 310 to 320 mg for women, and the Tolerable Upper Intake Level for magnesium from supplements is 350 mg a day, whichever form you choose [2]. Our Magnesium Glycinate Capsules provide 303 mg per 4-capsule serving, about 76 mg per capsule, so you can start with one or two capsules and build up. Take glycinate in the evening or split it across the day; if you use citrate for digestion or energy, take it earlier in the day. For all-day, all-round coverage, a multi-form blend like Magnesium Seven combines several forms. For detail, see how much magnesium glycinate per day.
Which magnesium is right for you?
Safety, Testing and Purity
Our magnesium glycinate is fully reacted (no oxide buffer) and made in UK GMP and BRC facilities. Our July 2026 batch was tested by Eurofins for magnesium content, heavy metals and microbes: lead measured 0.10 mg/kg against an EU limit of 3.0 mg/kg, and cadmium and mercury were below detection. The full report is under Test Results on the product page, and our method is explained in how we test and verify magnesium glycinate purity. Free from GMOs, gluten, dairy and fillers. For detail, see our Ingredients A to Z entry for Magnesium Glycinate.
Whatever the form, magnesium is not for everyone: people with kidney disease, heart block or myasthenia gravis, and anyone on interacting medicines such as some antibiotics, should check with their GP, doctor or pharmacist first. See who should not take magnesium.
Frequently Asked Questions
Which magnesium form absorbs best?
Citrate has the strongest head-to-head absorption data, and glycinate also absorbs well; both are far ahead of oxide, which showed about 4% fractional absorption in a human study. For everyday use, glycinate is usually the better pick because it is the gentlest on digestion.
Is magnesium glycinate better for sleep?
Glycinate is the form most people choose for an evening dose because it is gentle on the stomach and does not loosen stools at label doses. There is no authorised health claim linking magnesium to sleep; the authorised claims include normal functioning of the nervous system and normal psychological function.
Can I take magnesium glycinate and citrate together?
Yes. Citrate by day and glycinate at night is a common pairing, or use a multi-form blend. Count both towards your total: the NHS says 400 mg or less a day of magnesium from supplements is unlikely to cause any harm. In the US, the upper limit for magnesium from supplements is 350 mg a day.
Is magnesium oxide ever useful?
It can help short-term with constipation, because unabsorbed magnesium draws water into the bowel, but it is not ideal for ongoing supplementation due to low absorption.
What is the most gentle magnesium supplement?
Glycinate. It is the best tolerated of the three, and in a crossover trial in patients with ileal resection it was better tolerated by every patient than magnesium oxide.
What is the difference between magnesium citrate, glycinate and oxide?
They are the same mineral attached to different carriers: citric acid, the amino acid glycine, or oxygen. The carrier changes solubility, absorption and gut effect. Citrate and glycinate absorb well and oxide absorbs poorly; citrate and oxide can both loosen stools, glycinate rarely does.
Magnesium glycinate or oxide: which is better?
Glycinate for supplementation. Oxide contains more magnesium per gram, but only around 4% is absorbed in human testing, so little reaches your cells. A fully reacted glycinate such as ours delivers 303 mg elemental magnesium per serving in a form the gut tolerates.
What is better, magnesium citrate or magnesium glycinate?
For daily long-term use, glycinate: it is gentler on digestion and does not loosen stools at label doses. Citrate absorbs well too, and some prefer it during the day, accepting its mild laxative effect. Tolerance is the deciding factor.
Is a 400 mg magnesium oxide tablet better than magnesium glycinate?
No. A bigger number on the label does not mean more magnesium reaches your cells. Mg oxide tablets, common in US drugstores, often carry 400 mg or more of elemental magnesium (US Supplement Facts panels list the elemental amount [2]), but oxide showed about 4% fractional absorption in testing [1], and 400 mg is above the 350 mg US upper limit for supplements, set at the point where diarrhea becomes more likely. For daily use, a smaller dose of glycinate that you absorb and tolerate is the better choice; for occasional constipation, citrate is gentler than oxide.
References
- Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001;14(4):257-62. PubMed
- NIH Office of Dietary Supplements. Magnesium Fact Sheet for Health Professionals. NIH ODS
- 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. PubMed
- 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):183-91. PubMed
- 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):430-5. PubMed
- Pajuelo D, Meissner JM, Negra T, Connolly A, Mullor JL. Comparative Clinical Study on Magnesium Absorption and Side Effects After Oral Intake of Microencapsulated Magnesium (MAGSHAPE Microcapsules) Versus Other Magnesium Sources. Nutrients. 2024;16(24):4367. PubMed
- NHS. Vitamins and minerals: Others (magnesium). NHS
PubMed references verified against the NCBI database on 13 October 2026.
The sleep and calm specialist: Magnesium Glycinate, fully reacted bisglycinate, 303 mg elemental magnesium per serving, UK-made and third-party tested.
View productBen Law is the founder of Love Life Supplements and host of the Optimised Health Show. With over a decade of experience in clean, science-backed formulation, Ben focuses on filler-free, third-party tested supplements made in the UK. Learn more on the About page.