Magnesium Glycinate vs Citrate: What the Evidence Actually Shows

This article is for general education and is not medical advice. Nume supplements are not intended to diagnose, treat, cure, or prevent any disease.

What is the difference between magnesium glycinate and magnesium citrate?

Both deliver elemental magnesium, but the molecule attached to it differs. Glycinate binds magnesium to glycine, an amino acid. Citrate binds it to citric acid. That attached molecule is what changes how the supplement tends to sit with people, and it is the practical reason most people pick one over the other.

The rest of this article is about what the evidence does and does not support, because this is a category where the marketing has run well ahead of the research.

Is magnesium glycinate better absorbed than magnesium citrate?

There is no good evidence for that claim. It gets repeated constantly, but direct head-to-head human trials comparing glycinate and citrate absorption are scarce, and glycinate is largely absent from the comparative bioavailability literature that does exist.

The most-cited comparison of magnesium salts tested ten forms: oxide, chloride, sulphate, carbonate, acetate, pidolate, citrate, gluconate, lactate and aspartate. Glycinate was not among them. It also ran in magnesium-depleted rats rather than people, and found organic salts only slightly more available than inorganic ones, with gluconate highest (Coudray et al., 2005).

So if a brand tells you glycinate is the best-absorbed form, ask what they are citing. Usually the honest answer is nothing specific.

Which form of magnesium is poorly absorbed?

Magnesium oxide is the one with a genuine evidence problem. A human study of commercial magnesium preparations found relatively poor bioavailability for magnesium oxide, at around 4 percent fractional absorption, while magnesium chloride, lactate and aspartate were significantly higher and roughly equivalent to each other (Firoz and Graber, 2001).

Oxide is common because it is cheap and packs a lot of elemental magnesium per capsule. If a label shows a large magnesium number at a low price, it is worth checking which form it uses.

So why do people choose glycinate for the evening?

Tolerability, not absorption. Magnesium citrate is widely sold over the counter as a saline laxative, and that osmotic effect on the bowel is its best-known property. For someone taking magnesium nightly as part of a wind-down routine, that effect is usually unwanted.

Glycinate does not carry the same reputation, which is why it tends to be the form chosen for daily and evening use. That is a practical distinction about comfort and consistency. It is not a claim that one form works better.

Which magnesium form should you choose?

Match the form to the job rather than chasing an absorption ranking:

• Glycinate is generally chosen for daily or evening use, where the bowel effect of citrate would be unwelcome.
• Citrate is well studied and soluble, and its laxative effect is a feature for some people and a problem for others.
• Oxide is the cheapest per milligram and the weakest on absorption evidence.

The form you will actually take every day matters more than a few percentage points of theoretical absorption.

How much magnesium do you need?

Requirements vary by age and sex, and supplemental magnesium sits on top of what you already get from food. Leafy greens, nuts, seeds, legumes and whole grains are all meaningful sources. Read the label on your specific product for its elemental magnesium content, and speak with your healthcare provider before starting a supplement, particularly if you are pregnant, nursing, taking medication, or managing a health condition. Magnesium can interact with some medications.

Where Nume sits

Nume's Magnesium Calm uses magnesium glycinate, in a 90-capsule format, made in the USA. It is intended as daily support for relaxation and restful sleep as part of a balanced routine.

For anyone building an evening routine more broadly, our guide to apigenin and chamomile covers the other ingredient people ask about most.

Frequently asked questions

Can you take magnesium glycinate and citrate together?

They are different forms of the same mineral, so taking both means taking more total elemental magnesium than either alone. Check the combined amount against the labels, and speak with your healthcare provider before stacking magnesium products, especially alongside medication.

Does magnesium citrate cause diarrhoea?

Magnesium citrate is widely sold as an over-the-counter saline laxative, so a loosening effect on the bowel is its best-known property and the usual reason people switch away from it for daily use. Individual responses vary. Stop and speak with your healthcare provider if you have discomfort.

Is magnesium glycinate the most absorbable form of magnesium?

That claim is not well supported. Glycinate is largely absent from the comparative bioavailability studies that exist, so there is no strong basis for ranking it first. Glycinate is chosen mainly for tolerability in daily use rather than for demonstrated superior absorption.

When should you take magnesium glycinate?

Product labels differ and the instruction on your specific product is the one to follow. Many people take it in the evening as part of a wind-down routine. Consistency from day to day tends to matter more than the exact hour.

References

1. Coudray C, Rambeau M, Feillet-Coudray C, Gueux E, Tressol JC, Mazur A, Rayssiguier Y. Study of magnesium bioavailability from ten organic and inorganic Mg salts in Mg-depleted rats using a stable isotope approach. Magnes Res. 2005;18(4):215-223. PubMed 16548135
2. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001;14(4):257-262. PubMed 11794633