Magnesium Glycinate vs Citrate: Which Form Should You Take?

Glycinate or citrate — which magnesium should you actually take?

It is one of the most common supplement questions in the UK right now. Search "magnesium glycinate vs citrate" and you will find thousands of conflicting opinions, influencer recommendations, and marketing claims. The reality is less dramatic but more useful: these are two well-tolerated organic magnesium salts with different evidence profiles, and the right choice depends on what you value most — clinical data or marketing narrative.

This article breaks down both forms honestly, including where the evidence is strong, where it is thin, and why PARTICULAR chose the form it did.

What does magnesium do?

Before comparing forms, it is worth understanding why magnesium matters. It is an essential mineral involved in over 300 enzymatic reactions, and the following health claims are authorised under EU Regulation 432/2012 (retained in UK law):

• Contributes to normal muscle function
• Contributes to normal functioning of the nervous system
• Contributes to the reduction of tiredness and fatigue
• Contributes to normal psychological function
• Contributes to electrolyte balance
• Contributes to normal energy-yielding metabolism
• Contributes to the maintenance of normal bones and normal teeth

These claims apply to magnesium as a mineral — regardless of which form delivers it. The form determines how much of the magnesium your body can actually absorb.

How magnesium forms differ

Every magnesium supplement is a compound: elemental magnesium bonded to a "carrier" molecule. The carrier affects three things:

1. Elemental magnesium percentage — how much of the total weight is actual magnesium. Magnesium oxide is roughly 60% elemental magnesium by weight. Magnesium citrate is around 16%. Magnesium glycinate (bisglycinate) is approximately 14%. A higher percentage does not mean a better supplement — what matters is how much you absorb.

2. Solubility and absorption — the carrier molecule influences how readily the compound dissolves in the gut and how efficiently the magnesium crosses the intestinal wall. This is bioavailability.

3. Secondary effects — some carriers have their own biological activity. Glycine is an amino acid involved in neurotransmitter function. Citric acid is an organic acid that can have an osmotic effect at high doses.

Magnesium citrate

Magnesium citrate is magnesium bound to citric acid. It is one of the most extensively studied supplemental forms and has a strong evidence base for bioavailability.

What the research shows:

Lindberg et al. (1990) compared magnesium citrate and magnesium oxide in healthy volunteers. Magnesium citrate was significantly more soluble — 55% soluble in water versus virtually insoluble for oxide — and produced a significantly higher increment in urinary magnesium excretion, indicating superior absorption.

Firoz & Graber (2001) measured the bioavailability of four commercially available magnesium preparations in healthy volunteers. Magnesium oxide showed a fractional absorption of roughly 4%, while organic salts (including those with similar profiles to citrate) showed significantly higher absorption.

Walker et al. (2003) conducted a randomised, double-blind, placebo-controlled trial in 46 healthy individuals over 60 days. Magnesium citrate led to the greatest mean serum magnesium concentration compared with magnesium oxide and amino-acid chelate, following both acute and chronic supplementation. Magnesium oxide showed no significant difference from placebo.

Kappeler et al. (2017) confirmed these findings in a randomised cross-over study of 20 healthy males, showing higher urinary magnesium excretion and serum levels after a single dose of magnesium citrate compared with magnesium oxide.

The main drawback: at higher doses, the citric acid carrier can draw water into the bowel (an osmotic effect), potentially causing loose stools. This is dose-dependent and is the reason magnesium citrate is also used as a bowel preparation at very high clinical doses. At supplemental doses (100–200mg elemental), most people tolerate it well — but it is a legitimate consideration.

Magnesium glycinate (bisglycinate)

Magnesium glycinate — more precisely, magnesium bisglycinate — is magnesium chelated with two molecules of the amino acid glycine. It has become extremely popular, particularly through social media, where it is marketed as the "best" form for sleep, anxiety, and calm.

What the research shows:

The honest answer is: less than you might expect. There are far fewer clinical trials directly comparing glycinate with citrate in healthy human populations than the marketing would suggest.

Schuette et al. (1994) compared magnesium diglycinate with magnesium oxide in patients with ileal resection — a very specific clinical population with impaired absorption. They found evidence that some magnesium diglycinate may be absorbed intact via a dipeptide transport pathway, suggesting a potential alternative absorption route. However, this study cannot be generalised to healthy adults.

The glycine carrier itself is an inhibitory neurotransmitter precursor, which is part of the "calming" narrative. However, the amount of glycine delivered by a typical magnesium glycinate supplement (roughly 1–2g) is modest compared with the doses used in glycine-specific sleep research (typically 3g+). The calming reputation is plausible but not well-evidenced at supplemental magnesium doses.

To be clear: magnesium glycinate is not a bad form. It is well-tolerated, unlikely to cause GI issues, and the glycine carrier is harmless. The issue is the gap between how it is marketed and what has been demonstrated in comparative clinical trials.

Head-to-head comparison

Factor	Magnesium citrate	Magnesium glycinate
Bioavailability	High — demonstrated across multiple RCTs	Likely good — fewer direct comparisons
Evidence base	Strong — well-studied since 1990	Limited — few head-to-head human trials
Elemental Mg content	~16% by weight	~14% by weight
GI tolerance	Osmotic effect possible at high doses	Generally well-tolerated
Cost	Lower — widely available	Higher — chelation process costs more
Common marketing claim	"Best absorbed"	"Best for sleep and calm"
Best suited for	General supplementation with evidence-backed absorption	Those prioritising GI tolerance or who respond poorly to citrate

Other forms worth knowing

Magnesium oxide — contains the highest percentage of elemental magnesium (~60%) but has the poorest absorption. Firoz & Graber (2001) measured roughly 4% fractional absorption. It is cheap, which is why it dominates high-street multivitamins. Most of it passes straight through.

Magnesium threonate — marketed for cognitive function based on a single animal study suggesting it crosses the blood-brain barrier. Human data is extremely limited. It is expensive and contains very little elemental magnesium per dose.

Magnesium taurate — magnesium chelated with the amino acid taurine. Some emerging interest in cardiovascular contexts, but clinical evidence in humans remains early-stage. Not widely available in the UK.

Why PARTICULAR uses magnesium citrate

The decision was straightforward:

1. Evidence base — citrate has the deepest body of human bioavailability research among organic magnesium salts, with consistent results across multiple independent trials spanning over 30 years
2. Demonstrated absorption — Walker et al. (2003) showed citrate produced the highest serum magnesium levels of the forms tested, including amino-acid chelates
3. Regulatory standing — magnesium citrate is a well-established, EU-authorised source of magnesium for food supplements
4. Manufacturing compatibility — citrate works well with the microgranule coating process, maintaining stability through the enteric layer

We would rather use the form with the strongest evidence than the form with the strongest marketing.

How microgranules solve citrate's main drawback

The one genuine advantage glycinate holds over citrate is GI tolerance at higher doses. Citrate's osmotic effect — drawing water into the bowel — is the reason some people experience loose stools with standard magnesium citrate tablets or powders.

PARTICULAR's microgranule technology eliminates this problem:

• Each granule is individually enteric-coated, so the magnesium citrate passes through the stomach intact
• Release occurs in the upper intestine, where magnesium absorption is most efficient and where the osmotic effect is substantially reduced
• The dose is personalised from your questionnaire responses — not a one-size-fits-all amount, reducing the risk of exceeding your individual tolerance
• Magnesium is released independently from other minerals like calcium and zinc, avoiding competitive inhibition at absorption sites

In short: you get the bioavailability advantage of citrate without the GI compromise that makes some people reach for glycinate instead.

For a deeper look at how magnesium contributes to sleep quality specifically, see our article on magnesium for sleep.

Key takeaways

1. Both magnesium citrate and glycinate are well-tolerated organic magnesium forms — neither is a poor choice
2. Citrate has a significantly larger body of clinical evidence for bioavailability, demonstrated across multiple independent RCTs since 1990
3. Glycinate's reputation for "calm and sleep" is driven more by marketing than by comparative clinical data at supplemental doses
4. Magnesium oxide — the cheapest and most common form in high-street supplements — has roughly 4% absorption and is not a meaningful source
5. The main legitimate advantage of glycinate over citrate is GI tolerance at high doses — an advantage that enteric-coated microgranule delivery removes
6. Form matters, but so does dose — PARTICULAR's questionnaire calibrates your magnesium dose to complement your dietary intake, not replace it

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Sources cited in this article:

• Lindberg JS, Zobitz MM, Poindexter JR, et al. "Magnesium bioavailability from magnesium citrate and magnesium oxide." J Am Coll Nutr. 1990;9(1):48-55.
• Firoz M, Graber M. "Bioavailability of US commercial magnesium preparations." Magnes Res. 2001;14(4):257-62.
• Walker AF, Marakis G, Christie S, et al. "Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study." Magnes Res. 2003;16(3):183-91.
• 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.
• EU Commission Regulation 432/2012 — Authorised health claims made on foods.