Magnesium glycinate vs citrate: what each form does, and who actually runs low

Georgina Waugh, Clinical Nutritionist (BHSc Nutritional Medicine) · 10 minute read · Updated 14 September 2026

Magnesium glycinate vs citrate comes down to this: both absorb better than the oxide form, and citrate has more human absorption research behind it. What I could not find is a single trial comparing the two on anything you would actually feel, sleep and cramps included.

I get asked this most weeks, usually by someone who already owns one of each.

And the question underneath is rarely about the form. It is this: I take magnesium, nothing changed, so did I buy the wrong one?

Sometimes. More often, it is a question nobody asked before the first bottle. Were you actually low?

The short version

• Glycinate and citrate both absorb better than oxide, and citrate has more human research behind it than glycinate.
• “Glycinate for sleep, citrate for digestion” is marketing shorthand. No trial has compared the two head to head on sleep.
• The best recent sleep trial of glycinate found a small benefit, and people eating the least magnesium-rich food seemed to gain the most.
• About one in four Australian women aged 30 to 74 fall short on magnesium from food. Girls, younger women and women over 75 fall short more often.
• A normal blood test does not rule out a low intake, because only about 1% of your magnesium is in your blood.

What is the difference between magnesium glycinate and citrate?

Magnesium is always sold bound to something, and the partner is the word on the front of the bottle. Glycinate, often labelled bisglycinate, is magnesium attached to glycine, an amino acid. Citrate is attached to citric acid. Oxide is attached to oxygen.

The partner changes two things.

The first is how much of the capsule is magnesium at all. Glycine is heavy, so magnesium is only about 14% of magnesium glycinate by weight, against about 60% of magnesium oxide. A label that says 500 mg of magnesium glycinate is closer to 70 mg of magnesium.

Form	How much of it is magnesium	What the research found
Glycinate (bisglycinate)	About 14%	Better than oxide as an amino-acid chelate. No trial against citrate on symptoms
Citrate	About 16%	Highest blood levels in a 60-day trial, and the most human absorption research
Oxide	About 60%	The most magnesium by weight, and absorbed worst. No better than placebo on blood levels, and works as a laxative

The second is what happens in the gut, which is where “citrate for digestion” comes from. Magnesium that is not absorbed stays in the bowel and draws water in with it. In a Japanese trial of 90 adults with long-term constipation, magnesium oxide improved symptoms in 68% of people, against 12% on placebo.

So loosening things up is not a special talent of citrate. It is what magnesium does when it stays in the bowel, which is why oxide, the form that absorbs worst, works well as a laxative. Glycinate is often described as the gentler one, but I could not find a trial that measured that against citrate.

Which form actually gets into your body?

In a 60-day UK trial, 46 healthy adults took magnesium as citrate, as an amino-acid chelate (the family glycinate belongs to), as oxide, or a placebo. Judged by how much magnesium people passed in their urine, citrate and the chelate were both absorbed better than oxide. Citrate gave the highest blood levels, and oxide did no better than placebo.

A smaller 2019 study and a 2025 review of the absorption trials land in the same place: citrate absorbs well, oxide poorly.

Glycinate’s own record is thinner than its reputation. In a 2024 study of 40 adults, a single dose of bisglycinate did not measurably raise blood magnesium over six hours, while citrate did at four hours. It was funded by a company selling a different magnesium ingredient, and one afternoon says little about weeks of taking it. But it is not evidence that glycinate absorbs better, a claim you will read everywhere.

Does magnesium glycinate help sleep?

It is the reason most people give me for choosing glycinate, and there is now a decent trial.

In 2025, researchers in Germany gave 155 adults who reported poor sleep either magnesium bisglycinate or a placebo capsule every day for four weeks, without anyone knowing which they had. Four in five were women, the average age was 41, and sleep was scored on the Insomnia Severity Index, a questionnaire out of 28 where lower is better.

Fall in the Insomnia Severity Index (0 to 28, lower is better) over four weeks, with 95% confidence intervals as thin lines. The extra fall on magnesium was 1.6 points among everyone who started and 1.9 among those who took the capsules as directed. Schuster and colleagues, Nature and Science of Sleep, 2025.

Both groups slept better. The magnesium group’s score fell by 3.9 points and the placebo group’s by 2.3, so the part you could credit to the capsule was about 1.6 points. The researchers called that a small effect, and after four weeks the magnesium group was still, on average, in the range the scale calls subthreshold insomnia.

The part I find most useful is a side analysis: people who said they rarely ate magnesium-rich foods tended to improve more on the capsule. The researchers call it exploratory, because it rested on a single question.

An older trial in 100 adults over 51 points the same way. Sleep improved just as much on placebo, and magnesium only measurably raised blood levels in the participants who started low. A review of three small trials in older adults found people fell asleep about 17 minutes faster on magnesium, on evidence rated low or very low quality.

So if magnesium is going to help your sleep, it looks most likely when you were not getting enough to begin with. That makes the form the second question, not the first.

If your nights look more like wired at 11pm and awake at 3am, I have also written about what else produces that pattern.

Who actually runs low on magnesium in Australia?

The 2023 national nutrition survey compared what Australians usually eat with the average requirement for their age and sex. Three in ten Australians aged two and over fall short on magnesium from food and drink, women less often than men (27.3% against 35.2%).

Usual magnesium intake from food and drink for Australian women, 2023. Each bar covers the middle half of women in that age group, the darker line is the median, and the dashed line is the average requirement (265 mg a day, 260 mg from 18 to 29). The bold figure is the share below it. Supplements are not counted. Australian Bureau of Statistics.

Between 30 and 74, about one in four women fall short (26.0% to 28.1%). It rises at both ends: 43.9% of girls aged 12 to 17, 37.3% of women 18 to 29, and 39.6% of women 75 and over.

The survey counts food, not supplements, and it measures intake rather than what is in anyone’s body. Australia has never measured magnesium levels nationally, which I wrote about in what Australians are actually low in.

Food is not the only route to running low. Healthdirect lists type 2 diabetes, conditions such as Crohn’s disease, long-term vomiting or diarrhoea, kidney problems, alcohol dependency, and some long-term medicines including diuretics and reflux medicines. That last one is worth a second look: a review of nine studies covering 115,455 patients found people on reflux medicines were more likely to have low magnesium, although the studies varied too much for a firm number.

What I see in clinic. The pattern I meet most is a woman on her second or third magnesium, who has swapped forms because the first did not seem to work, and who has never written down what she eats in a day.

When we do, the gap is rarely the capsule. It is the days breakfast is a coffee, lunch is eaten at the desk, and there is not a nut, seed, legume or wholegrain in sight until dinner.

A different bottle does not change those days. Seeing them written down is where the useful conversation starts.

Chickpeas, quinoa and a handful of greens. Nothing in this bowl came out of a bottle, and it covers three of the food groups Healthdirect lists for magnesium.

Can a blood test tell if you are low in magnesium?

Sometimes. Only about 1% of your body’s magnesium is in your blood. Most is stored in bone, some of which can be released when needed, and the rest sits in muscle and soft tissue, as Healthdirect explains. So a low result means something, but a normal one does not prove your intake has been enough. Australia’s nutrient reference values say serum magnesium has not been properly validated as a reliable indicator of the body’s magnesium status.

It is the same trap as bloods that come back normal while you feel awful. The test still has a place: if you take a reflux medicine or a fluid tablet long term, have ongoing diarrhoea, or your GP is concerned about symptoms, it is a reasonable thing to ask about. It just cannot answer “should I be taking magnesium?” on its own.

What about leg cramps?

A Cochrane review of 11 trials found magnesium is unlikely to make a meaningful difference to the night-time leg cramps common in older adults, and in pregnancy the trials disagreed. Cramps that are new, severe or in one leg only, or come with swelling or redness, are a GP visit, not a supplement question.

Before you buy another bottle, try this

None of this costs anything, and it takes about twenty minutes over a week.

1. Turn your current bottle around and find the line that gives magnesium on its own, usually “equivalent to magnesium”. That is the number worth comparing, and if the form is oxide, you now know what the absorption trials found.
2. Write down three ordinary days of food, including one of the rushed ones, and put them through the free micronutrient calculator. It compares your magnesium with the Australian targets: for women, 310 mg a day from 19 to 30 and 320 mg a day from 31.
3. See where your magnesium came from. Healthdirect’s food list puts 30 g of pepitas at 159 mg, 30 g of almonds at 80 mg, half a cup of cooked brown rice at 72 mg and half a cup of cooked spinach at 57 mg.
4. If you take a reflux medicine or a fluid tablet long term, ask your GP whether checking your magnesium makes sense for you.

And before you swap to a different form, ask yourself:

• Did I start magnesium because I was low, or because someone said it helps with sleep?
• What else changed in the month I started it?
• How many days this week did I eat nuts, seeds, legumes or wholegrains?
• Am I on a medicine that can lower magnesium?
• If it stopped working tomorrow, would I actually notice?

If your three days come back short, food is the first place to close the gap. If they come back fine and you are still sleeping badly, magnesium was probably never the answer, and that is worth knowing too.

Not sure magnesium is even the right question?

In a free 15-minute call we look at what you eat, what you already take and what is going on with your sleep or energy, and work out what is worth checking first.

Book a free 15-minute call

Fifteen minutes, on the phone, and nothing to buy to book it.

Common questions

Is magnesium glycinate or magnesium citrate better?

Neither has been shown to be better at anything you would feel, because no trial has compared them head to head on sleep, cramps or energy. Citrate has more human research on absorption. Whether you were low to begin with matters more than the form.

What is the downside of magnesium glycinate?

Magnesium is only about 14% of magnesium glycinate by weight, so it takes more of the compound to deliver the same magnesium. Its reputation for better absorption is not well supported by human studies. Like any magnesium supplement, too much can cause diarrhoea, nausea and stomach cramps.

Which is better for leg cramps, magnesium citrate or magnesium glycinate?

There is no good evidence that either form helps ordinary leg cramps. A Cochrane review found magnesium in any form is unlikely to make a meaningful difference to night-time cramps in older adults. Cramps that are new, severe or in one leg only should be checked by a GP.

What should you never mix with magnesium?

Two cautions from Australian guidance. Some magnesium products also contain vitamin B6, listed as pyridoxine or pyridoxal 5-phosphate, so stop taking them and see your doctor if you notice tingling, burning or numbness. And some long-term medicines, including diuretics and reflux medicines, can lower magnesium. For anything else you take, ask your pharmacist whether the timing matters.

Which magnesium is best for seniors?

No form has been shown to be best for older adults. What stands out is intake: 39.6% of Australian women and 50.2% of men aged 75 and over do not get enough magnesium from food. Your kidneys clear extra magnesium, so anyone with kidney problems should check with their GP before taking a supplement.

Sources

1. PubChem, magnesium glycinate, trimagnesium dicitrate and magnesium oxide: molecular formulas and weights. National Library of Medicine.
2. Morishita D and colleagues. Senna versus magnesium oxide for chronic constipation: a randomised, placebo-controlled trial. American Journal of Gastroenterology, 2021.
3. Walker AF and colleagues. Magnesium citrate found more bioavailable than other magnesium preparations in a randomised, double-blind study. Magnesium Research, 2003.
4. Werner T and colleagues. Bioavailability of magnesium from magnesium citrate and magnesium oxide, measured by urinary excretion. Magnesium Research, 2019.
5. Merschmann R and colleagues. Bioavailability of magnesium and potassium salts: a review. Molecular Nutrition and Food Research, 2025.
6. Pajuelo D and colleagues. Magnesium absorption and side effects after microencapsulated magnesium versus other magnesium sources. Nutrients, 2024. Funded by the ingredient manufacturer.
7. Schuster J and colleagues. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomised, placebo-controlled trial. Nature and Science of Sleep, 2025.
8. Nielsen FH and colleagues. Magnesium supplementation improves indicators of low magnesium status in adults older than 51 years with poor quality sleep. Magnesium Research, 2010.
9. Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies, 2021.
10. Australian Bureau of Statistics. Australian Health Survey: Usual Nutrient Intakes, 2023. Minerals, magnesium.
11. Healthdirect. Magnesium deficiency.
12. Park CH and colleagues. Proton pump inhibitor use and the risk of low magnesium: a systematic review and meta-analysis. PLoS One, 2014.
13. Healthdirect. Magnesium blood test.
14. National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: magnesium. Eat For Health.
15. Garrison SR and colleagues. Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews, 2020.
16. Healthdirect. Foods high in magnesium. Values from the Australian Food Composition Database.
17. Healthdirect. Magnesium and your health.

Important: This article is general information written by a clinical nutritionist. It is not medical advice and does not replace care from your GP or another qualified health professional. Functional testing does not diagnose, treat, cure or prevent any condition, and results are best interpreted alongside your symptoms, history, medications and supplements.

Written and reviewed by Georgina Waugh

Clinical Nutritionist, BHSc Nutritional Medicine

Last updated: 14 September 2026

Sources reviewed: Healthdirect and NHMRC guidance, the ABS 2023 usual nutrient intakes, a Cochrane review, three further reviews and six clinical trials of magnesium absorption, sleep and constipation.