Magnesium Glycinate vs Citrate: What Actually Separates Them

Magnesium glycinate and magnesium citrate are both well absorbed forms of magnesium, and the real difference between them is what they do in your gut. Citrate draws water into the intestine, which loosens stools at higher doses. Glycinate is chelated to the amino acid glycine, produces far less of that osmotic effect, and is usually the easier one to take every day. Absorption is close enough between the two that tolerance, not bioavailability, should decide it.

If you have picked up two magnesium bottles and found yourself squinting at the small print trying to work out why one says 1500mg and the other says 1480mg, and why neither number seems to mean what you thought it meant, that is a completely reasonable reaction. The labels on magnesium supplements are among the most misleading in the entire supplement aisle, and it is not always deliberate.

So here is the comparison of magnesium glycinate vs citrate without the marketing, including the one trial that actually put these two forms head to head, and the two label traps almost nobody explains.

Magnesium glycinate vs citrate at a glance

Is magnesium glycinate the same as magnesium bisglycinate?

Yes. Magnesium bisglycinate is the chemically precise name, because one magnesium ion is bound to two glycine molecules, and bi means two. Glycinate is the shorter trade name for the same compound. If you are comparing two products and one says glycinate while the other says bisglycinate, that difference alone tells you nothing, and it is not a reason to pay more.

Which is better absorbed, magnesium glycinate or citrate?

Direct head to head evidence between glycinate and citrate is thin, and any article that tells you one is definitively superior is going beyond what the research shows. The best available comparison is a randomised, double blind, placebo controlled trial run at the University of Reading. Forty six healthy adults took 300mg of elemental magnesium a day for 60 days, as either an amino acid chelate, citrate or oxide.

The findings were more interesting than the internet consensus suggests. Citrate produced the highest mean serum magnesium of any group after both a single dose and 60 days of daily use. Both organic forms, the chelate and the citrate, showed greater absorption than oxide as measured by 24 hour urinary magnesium excretion. Magnesium oxide performed no better than placebo on any measure.

A separate study screened 15 commercially available magnesium formulations using a simulated human gut model, then took the best and worst performers into a live trial with 30 people. It found that how well a formulation dissolves predicts how well it is absorbed, which matters more than the name on the tub. Roughly 30% of the magnesium you swallow is absorbed in the intestine, and that figure moves with dose, with how much magnesium you already have on board, and with what else is in your stomach at the time.

The real difference is what happens in your gut

Citrate is highly soluble. Once it dissolves, it pulls water into the intestinal lumen by osmosis, which softens stool and speeds transit. That is why higher strength magnesium citrate is used in bowel preparation before medical procedures, and it is the property that decides whether citrate suits you.

The threshold is more precise than most people realise. European safety assessment work identified mild diarrhoea in a small proportion of adults at supplemental magnesium doses of roughly 360mg to 365mg a day, which is the lowest observed adverse effect level. Below that, most people notice nothing. Above it, the odds of a looser bowel habit rise, and they rise faster with citrate than with glycinate.

Glycinate behaves differently because the magnesium arrives already bound to glycine rather than dissociating into free ions the moment it hits water. Less free magnesium in the intestine means less osmotic pull. In practice, if you have tried magnesium before and given up because of the effect on your stomach, glycinate is the form to try next.

Elemental magnesium is the only number on the label that matters

This is where most people go wrong, and it is not their fault. A magnesium supplement label usually carries two numbers, and they measure completely different things.

The first is the weight of the whole compound. The second is the elemental magnesium, meaning the actual magnesium atoms inside that compound. Magnesium is always bound to a partner molecule, and the partner has weight. Fully reacted magnesium bisglycinate is only about 14% magnesium by weight, because the two glycine molecules make up the other 86%. So 1000mg of pure bisglycinate delivers roughly 140mg of elemental magnesium, not 1000mg.

The UK Nutrient Reference Value used on supplement labels is 375mg of magnesium a day. The NHS figures for what adults aged 19 to 64 actually need are lower, at 300mg a day for men and 270mg a day for women, and most of that should come from food. Always compare products on elemental magnesium, never on the compound weight printed in the largest font.

Why some magnesium labels say buffered, and what that means for you

Look at the bottom two rows of that table again. A 1500mg serving of bisglycinate should give about 210mg of elemental magnesium if it were fully reacted, yet the label says 300mg. That is not an error. It means the formula is buffered.

Buffering means the chelate or salt has been blended with magnesium oxide. Oxide is roughly 60% elemental magnesium by weight, far denser than either glycinate or citrate, so adding some of it lifts the elemental total considerably. The reason manufacturers do this is practical rather than sinister. A fully reacted bisglycinate delivering 300mg of elemental magnesium would need around six large capsules a day, which almost nobody takes consistently.

Can you take magnesium glycinate and citrate together?

Yes, and combining forms is a recognised formulation strategy rather than a mistake. Different magnesium compounds use partly different absorption routes, so a blend can spread the load rather than saturating one pathway. The thing to watch is the total. Add up the elemental magnesium from everything you take, not the compound weights, and keep the combined figure sensible.

If a blend appeals, a purpose built multi form product is usually simpler than stacking two single form bottles, and our Magnesium Complex 6-in-1 does exactly this, combining six magnesium forms with zinc, vitamin D and vitamin B6. We explain the reasoning behind multi form blends in more detail in our guide to how the 6-in-1 complex works and who it suits.

So which should you take?

Neither form is better in the abstract. Pick based on your digestion and on what you want the supplement to do.

If your interest in magnesium is specifically about sleep or anxiety rather than the citrate and glycinate comparison, that is a different question with a different answer, and we cover it properly in our guide to which type of magnesium suits sleep, anxiety and overall health.

How the two VitaBright options compare

We make both forms, and we would rather you took the one that suits your gut than the one with the biggest number on the front.

Both are made in BRC grade AA accredited UK facilities to GMP standards, with independently verified heavy metal testing and double sealed bottles. You can see the full detail on the Magnesium Glycinate and Magnesium Citrate pages, and the judging notes behind those awards in our write up of the BBC Good Food magnesium results.

Safety, upper limits and medicines

Magnesium is well tolerated by most healthy adults, and the dose limiting effect is almost always a looser bowel habit rather than anything serious. There are still situations worth knowing about.

• If you have chronic kidney disease or reduced kidney function, speak to your GP before taking any magnesium supplement. Impaired excretion can allow magnesium to build up.
• Magnesium reduces the absorption of tetracycline and quinolone antibiotics. Take it at least 2 hours before, or 4 to 6 hours after, those medicines.
• Separate magnesium from levothyroxine by at least 4 hours, and follow the leaflet timing for bisphosphonates.
• Long term proton pump inhibitor use has been linked to low magnesium levels, so mention any supplement to your prescriber.
• If you are pregnant or breastfeeding, check with your GP or midwife before starting.

If you are unsure how much you actually need rather than which form to take, we cover that separately in how much magnesium is the right dosage for you, and if you are trying to work out whether you are running low in the first place, start with the common signs of magnesium deficiency.

References

1. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study Walker AF, Marakis G, Christie S, Byng M. Magnesium Research, 2003;16(3):183-191.
2. Predicting and Testing Bioavailability of Magnesium Supplements Blancquaert L, Vervaet C, Derave W. Nutrients, 2019;11(7):1663.
3. Safety of magnesium l-threonate as a novel food, including the SCF tolerable upper intake level for supplemental magnesium EFSA Panel on Nutrition, Novel Foods and Food Allergens. EFSA Journal, 2024.
4. Vitamins and minerals: others (magnesium) NHS.
5. Proton pump inhibitors in long-term use: reports of hypomagnesaemia MHRA Drug Safety Update.

This article is for general information and is not a substitute for medical advice. Food supplements should not be used in place of a varied and balanced diet or a healthy lifestyle. If you are pregnant, breastfeeding, taking medication or have an existing health condition, speak to your GP before starting a new supplement.