Types of Magnesium: Every UK-Permitted Form and Its Elemental Dose

UK law lists 23 magnesium compounds a food supplement may use, the latest two added in 2023 (magnesium citrate malate) and 2026 (magnesium L-threonate monohydrate, which also needed a novel-food authorisation). Each is magnesium bound to something else, so the share of magnesium by weight runs from about 60% for oxide to about 6% for gluconate.^{1, 2} The directory below gives every form, its status and its elemental magnesium; no form is ranked. It sits inside the Wellgard vitamins and minerals guide.

Sources checked on 4 November 2026.

Which forms of magnesium can a UK supplement contain?

The 23 entries of Schedule 2 to the Nutrition (Amendment etc.) (EU Exit) Regulations 2019, the GB list that the Food Supplements (England) Regulations 2003 point to: the 21 carried over from Annex II of the food supplements directive, from magnesium acetate to magnesium acetyl taurate, plus magnesium citrate malate, inserted on 10 February 2023, and magnesium L-threonate monohydrate, inserted on 5 March 2026 for Scotland and Wales and on 12 August 2026 for England.¹ The directive's Annex II on legislation.gov.uk is the pre-2021 origin of that list, published for cross-reference and not amended since; the Schedule is the text that counts. Magnesium L-threonate therefore sits on the Schedule and on the Food Standards Agency register (NOVEL-166), which shows it authorised as a novel food in England, Scotland and Wales from 5 March 2026, for adults only, excluding pregnant and lactating women, at a maximum of 250 mg of magnesium a day, stated on the label.² England's purity criteria (magnesium assay 7.2 to 8.3%) took effect on 13 August 2026.³ The European assessment found it safe at up to 3,000 mg a day for adults "except for pregnant and lactating women"; it assessed safety, not effects.⁴

Whatever the salt, the wording belongs to the mineral: "Magnesium contributes to normal muscle function" is one of ten authorised wordings in the Great Britain register, usable where a serving supplies at least 15% of the 375 mg reference value, 56.25 mg of magnesium; no form has a wording of its own.^{5, 6}

How much magnesium is in each form?

From about 60% (oxide) to about 6% (gluconate). Every percentage here is calculated from the formula, so the panel line "magnesium ... mg (% NRV)" is the figure to read against the NHS amounts of 300 mg a day for men and 270 mg for women aged 19 to 64 (page reviewed 3 August 2020).^{6, 7} Worked examples: 500 mg of bisglycinate about 50 to 70 mg of magnesium; 500 mg of citrate 40 to 80 mg; 500 mg of oxide about 300 mg; 2,000 mg of L-threonate about 145 to 165 mg.

What are all the types of magnesium, and where is each covered?

Which magnesium forms are medicines rather than supplements?

Five, as the formulary describes them: magnesium hydroxide for "Constipation"; magnesium citrate with sodium picosulfate for "Bowel evacuation on day before radiological examination, endoscopy, or surgery"; magnesium aspartate for "Treatment and prevention of magnesium deficiency"; magnesium glycerophosphate for "Hypomagnesaemia"; and magnesium sulfate, by injection or infusion, for "Severe acute asthma" and other hospital uses.^{9, 10, 11, 12, 13} The aspartate and glycerophosphate monographs both say "Magnesium preparations may not be interchangeable due to differences in bioavailability".^{9, 12}

Which forms are not permitted in UK supplements?

Any compound not on the Schedule: orotate, aspartate (a medicine here), bicarbonate in solution, tartrate, fumarate and rarer salts. "Not on the list" is a legal fact.¹

Is glycinate the same as bisglycinate, and are the phosphates one form or three?

Yes: glycinate, bisglycinate and diglycinate are one compound, magnesium with two glycine molecules, which the law names "magnesium bisglycinate".¹ Its human data are small: in 12 people with part of the small bowel removed, a 100 mg isotope dose was absorbed no differently from oxide overall (23.5% against 22.8%), better in the four poorest absorbers, and "better tolerated by all patients"; in 46 healthy adults on 300 mg a day for 60 days, an amino-acid chelate and citrate raised urinary magnesium more than oxide, and red-cell magnesium did not differ between groups.^{14, 15}

The phosphates are one legal entry, "magnesium salts of orthophosphoric acid", covering three salts: monomagnesium (8.4% magnesium as the tetrahydrate), dimagnesium (13.9% as the trihydrate) and trimagnesium phosphate (27.7% dry, 17.9% as the octahydrate); "magnesium phosphate" on a label could mean any of them, so read the panel.¹

What we don't know

• Which salt is best absorbed. The 2017 review concluded that "it remains unclear which Mg2+ binding form produces the highest bioavailability" and that dose and existing status matter more.¹⁶ The studies disagree: a urine-based comparison found oxide at 4% fractional absorption, with chloride, lactate and aspartate "significantly higher and equivalent"; a crossover in 41 adults found 520 mg a day as oxide raised cell magnesium where 296 mg as citrate did not; and an unpublished 2007 crossover of 14 healthy volunteers, summarised in a 2018 European assessment of a manufacturer's dossier, put oxide lowest of four forms on a 24-hour serum curve after a single 150 mg dose, with a buffered bisglycinate highest (0.109 against 0.225, 0.196 for di-magnesium malate and 0.164 for bisglycinate, units not stated).^{17, 18, 23}
• What threonate does in people. Four placebo-controlled trials: in 44 adults with cognitive impairment, a cognition score improved over 12 weeks (developer-employed authors) and sleep and anxiety effects "could not be determined"; in 109 women after breast-cancer surgery, no difference in pain, mood, sleep or cognition over 12 weeks; in a supplier-funded 21-day trial of 80 adults, wearable sleep scores beat placebo; and in a six-week trial of 100 adults aged 18 to 45 with self-reported dissatisfied sleep, funded by the ingredient's developer, 2 g a day of a branded threonate improved a composite cognition score more than placebo (p = 0.043) and self-reported sleep-related impairment, while sleep disturbance, restorative sleep and the wearable's sleep measures did not differ; a correction in October 2026 changed a statistical wording only. None measured brain magnesium.^{19, 20, 21, 22}
• The EU list that Northern Ireland follows. It moves on its own timetable, and an EU decision does not change the GB text.

Frequently asked questions

What is chelated magnesium?

Magnesium bound to an organic molecule such as glycine (bisglycinate), lysine (lysinate) or taurine (taurate). The two published human chelate studies above, and the unpublished 2007 crossover, found better tolerance or uptake than oxide on some measures, not an effect beyond the magnesium; "chelated" describes the compound and claims nothing.^{14, 15, 23}

What is the difference between magnesium oil, flakes and Epsom salt?

Oil and flakes are magnesium chloride, usually the hexahydrate at 12.0% magnesium; Epsom salt is magnesium sulphate heptahydrate at 9.9%. Both are bath or skin products, not food supplements.

Is magnesium aspartate a supplement in the UK?

No. It is not among the 23 listed sources; in the UK it is a medicine for "Treatment and prevention of magnesium deficiency".^{1, 9} In the one absorption comparison that included it, it matched chloride and lactate.¹⁷

What is a magnesium complex?

Two or more listed salts in one serving: the ingredients list names each compound, and the nutrition panel's single magnesium figure is the dose.⁶ No trial has compared a blend with a single salt; how to choose a magnesium supplement covers blends and "buffered" labels.

Sources

1. The Nutrition (Amendment etc.) (EU Exit) Regulations 2019, SI 2019/651, Schedule 2 Part B: mineral substances which may be used in the manufacture of food supplements. Latest available (revised) text, read 4 November 2026; footnotes F2 (magnesium citrate malate inserted 10 February 2023 by SI 2023/28), F3 and F4 (magnesium L-threonate monohydrate inserted 5 March 2026 for Scotland and Wales and 12 August 2026 for England). legislation.gov.uk. Origin of the list: Directive 2002/46/EC, Annex II, legislation.gov.uk.
2. FSA regulated products register, NOVEL-166: magnesium L-threonate monohydrate. Last updated 5 March 2026. data.food.gov.uk.
3. SI 2026/680: Food Supplements Purity Criteria (Magnesium L-threonate monohydrate) (England) Regulations 2026. legislation.gov.uk.
4. EFSA NDA Panel. Safety of magnesium L-threonate as a novel food pursuant to Regulation (EU) 2015/2283 and bioavailability of magnesium from this source. EFSA Journal, 2024. PubMed 38481468.
5. Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register. Updated 19 May 2026. gov.uk.
6. Retained Regulation (EU) No 1169/2011, Annex XIII: nutrient reference values and the 15% rule. legislation.gov.uk.
7. NHS. Vitamins and minerals: others, including magnesium. Page last reviewed 3 August 2020 (review overdue). nhs.uk.
8. EFSA NDA Panel. Magnesium citrate malate as a source of magnesium added for nutritional purposes to food supplements. EFSA Journal, 2018. PubMed 32625777.
9. BNF. Magnesium aspartate. bnf.nice.org.uk.
10. BNF. Magnesium hydroxide. bnf.nice.org.uk.
11. BNF. Magnesium citrate with sodium picosulfate. bnf.nice.org.uk.
12. BNF. Magnesium glycerophosphate. bnf.nice.org.uk.
13. BNF. Magnesium sulfate. bnf.nice.org.uk.
14. Schuette SA, et al. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. JPEN Journal of Parenteral and Enteral Nutrition, 1994. Randomised crossover, 12 patients, single dose; US public research funding listed on PubMed (NIH and FDA grants). PubMed 7815675.
15. Walker AF, et al. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research, 2003. Randomised placebo-controlled trial, 46 adults, 60 days; research support from a source other than the US government listed on PubMed, funder not named. PubMed 14596323.
16. Schuchardt JP, Hahn A. Intestinal absorption and factors influencing bioavailability of magnesium: an update. Current Nutrition and Food Science, 2017. Narrative review; funding not stated on PubMed. PubMed 29123461.
17. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research, 2001. Urinary study, healthy volunteers (number not in abstract), four salts; funding not stated on PubMed. PubMed 11794633.
18. Shechter M, et al. Comparison of magnesium status using X-ray dispersion analysis following magnesium oxide and magnesium citrate treatment of healthy subjects. Magnesium Research, 2012. Randomised crossover, 41 adults, one month each; funding not stated on PubMed. PubMed 22433473.
19. Liu G, et al. Efficacy and safety of MMFS-01, a synapse density enhancer, for treating cognitive impairment in older adults: a randomized, double-blind, placebo-controlled trial. Journal of Alzheimer's Disease, 2016. 44 adults aged 50 to 70, 12 weeks; authors employed by the developer. PubMed 26519439.
20. Ni Y, et al. A randomized, double-blind, placebo-controlled trial to evaluate the therapeutic effect of magnesium-L-threonate supplementation for persistent pain after breast cancer surgery. Breast Cancer: Targets and Therapy, 2023. 109 women, 12 weeks; no conflicts declared. PubMed 37520407.
21. Hausenblas HA, et al. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: a randomized controlled trial. Sleep Medicine: X, 2024. 80 adults aged 35 to 55, 1 g a day for 21 days; supplier-funded. PubMed 39252819.
22. Lopresti AL, Smith SJ. Frontiers in Nutrition, 2025 (correction October 2026). Randomised placebo-controlled trial of a branded magnesium L-threonate, 100 adults aged 18 to 45, 2 g a day for 6 weeks; funded by the ingredient's developer, which took part in the design; the lead author directs a contract-research company funded by supplement makers. PubMed 41601871; correction PubMed 42959782.
23. EFSA ANS Panel. Evaluation of di-magnesium malate, used as a novel food ingredient and as a source of magnesium. EFSA Journal, 2018. Regulatory opinion on a manufacturer's dossier, summarising an unpublished 2007 four-arm crossover in 14 healthy volunteers (section 3.4.1). PubMed 32625931.

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This article is general information, not medical advice: with kidney disease or prescription medicines, ask your pharmacist or GP first.