Which Magnesium Is Best? Glycinate vs Citrate vs Threonate (UK)
The short answer: there is no single best form. Glycinate suits most people who want a daily supplement, citrate is a well-absorbed lower-cost option that can loosen stools, and threonate is a niche, pricier form with little magnesium per capsule. What matters most is elemental magnesium per dose: the NHS says 400 mg or less a day from supplements is unlikely to cause harm.
Magnesium has become one of the most talked-about supplements, and US brands now sell it in a dozen forms with very different prices and promises. This guide cuts through it: what the NHS says about how much you need, how to read "elemental magnesium" on a label, how the three most popular forms differ, which health claims are actually allowed in Great Britain, and the magnesium products we stock in each form.
How much magnesium do you need?
According to the NHS page on vitamins and minerals, adults aged 19 to 64 need about 300 mg a day (men) and 270 mg a day (women), and most people should be able to get this from a varied diet. Good sources include spinach, nuts and wholemeal bread. The NHS adds two points that matter when choosing a supplement:
- taking high doses of magnesium (more than 400 mg) for a short time can cause diarrhoea;
- having 400 mg or less a day of magnesium from supplements is unlikely to cause any harm.
So a supplement isn't a must for most people. If you choose to take one, keep the total from supplements at or below 400 mg of elemental magnesium a day, and speak to your GP or pharmacist first if you have kidney disease or take prescribed medicines, as magnesium can affect how some medicines are absorbed.
The label trick: compound weight vs elemental magnesium
This is where most confusion comes from. A label might say "magnesium glycinate 500 mg" or "magnesium L-threonate 2,000 mg". That figure is often the weight of the whole compound (magnesium plus the molecule it's bound to). The number that matters is elemental magnesium, the amount of magnesium itself, which is usually much lower. Look for "elemental" in the supplement facts panel, and check how many capsules make one serving. Here are real examples from products we stock:
| Product | Form | Serving size | Elemental magnesium per serving |
|---|---|---|---|
| Nutricost Magnesium Glycinate (180 capsules) | Bisglycinate | 3 capsules | 210 mg |
| Nature Made Magnesium Glycinate (180 capsules) | Bisglycinate | 2 capsules | 200 mg |
| Doctor's Best Magnesium Lysinate Glycinate (120 capsules) | Glycinate (chelated) | 2 capsules | 105 mg |
| NOW Foods Magnesium Bisglycinate Powder (227 g) | Bisglycinate | 1 level teaspoon (about 2.5 g) | 250 mg |
| Double Wood Magnesium Citrate (180 capsules) | Citrate | 2 capsules (800 mg citrate) | 112 mg |
| Pure Encapsulations Magnesium Citrate/Malate | Citrate and malate | 1 capsule | 120 mg |
| Garden of Life Magnesium Citrate Gummies (60) | Citrate | 4 gummies | 400 mg |
| Double Wood Magnesium L-Threonate (120 capsules) | L-threonate (Magtein) | See label (2,000 mg compound) | Check label; threonate supplies far less elemental magnesium than its compound weight |
| Life Extension Neuro-Mag (90 capsules) | L-threonate | See label | Check label |
Notice the Double Wood citrate: 800 mg on the front, 112 mg of actual magnesium. And note that a full serving of the Garden of Life gummies already reaches the NHS 400 mg line on its own, so don't combine it with another magnesium product; you can take fewer gummies.
Glycinate vs citrate vs threonate
Magnesium glycinate (bisglycinate)
Magnesium bound to the amino acid glycine. It is usually marketed as gentle on the stomach, which is why it has become the default choice for daily use. Capsules tend to be large and you often need two or three per serving, so a powder is an alternative if you struggle with tablets. Choose this if you want a straightforward daily magnesium supplement.
Magnesium citrate
Magnesium bound to citric acid. It dissolves well in water and is widely used. At higher doses it is more likely to loosen stools, which is consistent with the NHS warning about diarrhoea above 400 mg. It is often the lower-cost option per milligram of magnesium. Choose this if you want an everyday form at a lower price, or prefer a gummy or powder. Some citrate products are sold in the US as laxatives; we haven't included those here.
Magnesium L-threonate
Magnesium bound to threonic acid, a form sold under the trademark Magtein. It is heavily marketed for "brain" benefits, but this is an area of early research, and no brain or memory claim for magnesium is authorised in Great Britain. It is also the most expensive way to buy magnesium and supplies relatively little elemental magnesium per capsule. Choose this only if you specifically want to try this form and accept the higher cost; it is not needed to meet your daily magnesium requirement.
Other forms you'll see
Malate (bound to malic acid) is often combined with citrate. Oxide contains a high proportion of magnesium by weight and is common in cheap tablets and multivitamins. Taurate is bound to taurine. Whatever the form, the same rule applies: check elemental magnesium per serving and stay within 400 mg from supplements.
What magnesium can and can't claim in the UK
Supplement claims in Great Britain must appear on the GB Nutrition and Health Claims Register. For magnesium, the authorised claims are that it contributes to:
- a reduction of tiredness and fatigue;
- electrolyte balance;
- normal energy-yielding metabolism;
- normal functioning of the nervous system;
- normal muscle function;
- normal protein synthesis;
- normal psychological function;
- the maintenance of normal bones and teeth;
- and that it has a role in the process of cell division.
Several claims you'll see on US labels, for example that magnesium regulates blood pressure or blood sugar, are listed on the register as not authorised. There is no authorised claim that magnesium improves sleep, and none that a particular form improves memory or brain function. Many people take magnesium in the evening as part of a wind-down routine, and that's fine, but treat sleep or "brain" promises on US packaging with caution. If you have ongoing problems with sleep, low mood or fatigue, speak to your GP.
A quick decision guide
| If you want... | Consider | From our range |
|---|---|---|
| A simple daily supplement | Glycinate capsules | Nutricost or Nature Made glycinate |
| A lower dose you can build up | Smaller-dose glycinate | Doctor's Best (105 mg per 2 capsules) |
| No capsules | Powder or gummies | NOW Foods powder or Garden of Life gummies |
| A budget everyday form | Citrate | Double Wood citrate or Pure Encapsulations citrate/malate |
| To try the threonate form | L-threonate | Double Wood or Life Extension Neuro-Mag |
Compare more in our magnesium collection. Some products in that range combine magnesium with other ingredients such as melatonin or herbal extracts; read labels carefully, as melatonin is a prescription-only medicine in the UK and we don't recommend those combinations.
Food first
For most adults, food can cover the 270 to 300 mg daily need. The NHS lists spinach, nuts and wholemeal bread as sources. Building meals around green vegetables, wholegrains, nuts, seeds and pulses is the simplest route. If you're also thinking about winter vitamins, our vitamin D in winter guide covers the NHS advice to consider 10 micrograms a day during autumn and winter, and our multivitamin guide explains how to check for doubled-up minerals.
How we chose
We began with the NHS daily amounts and the 400 mg supplement threshold, then checked the supplement facts on every product page for elemental magnesium and serving size, rather than the headline compound weight. We excluded products combining magnesium with melatonin, products sold as laxatives, and blends with long lists of herbal extracts, so the comparison stays about magnesium itself. We only describe benefits using claims authorised on the GB register, even where a US label says more. We favoured established US-market brands that can be harder to find on UK shelves, and covered capsules, powder and gummies. We don't show star ratings because we don't yet have enough verified customer reviews, and no brand paid to be included. All orders come with free UK delivery and free 30-day returns.
Checklist
- Adults need about 270 mg (women) to 300 mg (men) of magnesium a day; most can get it from food.
- From supplements, stay at or under 400 mg of elemental magnesium a day.
- Read "elemental magnesium per serving", not the compound weight on the front.
- Glycinate for everyday use, citrate for value, threonate only if you want that specific form.
- Ignore sleep and "brain" promises; no such magnesium claim is authorised in Great Britain.
- Ask your GP or pharmacist first if you have kidney problems or take prescribed medicines.
Frequently asked questions
Which form of magnesium is best?
There is no single best form. Glycinate suits most people who want a daily supplement, citrate is a good-value option that can loosen stools at higher doses, and threonate is a costly niche form. Elemental magnesium per dose matters more than the form.
How much magnesium should I take a day?
The NHS says adults aged 19 to 64 need about 300 mg (men) or 270 mg (women) a day, usually from food. Taking 400 mg or less a day from supplements is unlikely to cause harm.
What does elemental magnesium mean?
It is the amount of magnesium itself in a serving, rather than the weight of the whole compound. For example, 800 mg of magnesium citrate in one product we stock provides 112 mg of elemental magnesium.
Does magnesium help you sleep?
There is no authorised health claim in Great Britain that magnesium improves sleep. Authorised claims include contributing to normal functioning of the nervous system and to a reduction of tiredness and fatigue.
Is magnesium glycinate better than citrate?
Glycinate is usually marketed as gentler on the stomach, while citrate is more likely to loosen stools at higher doses and is often cheaper. Both are widely used; choose based on tolerance, format and elemental dose.
Is magnesium L-threonate worth it?
It is the most expensive form and supplies relatively little elemental magnesium per capsule. Brain and memory benefits are an area of early research, and no such claim is authorised in Great Britain.
Can I take magnesium with other medicines?
Magnesium can affect how some medicines are absorbed, so ask your GP or pharmacist before taking it if you take prescribed medicines or have kidney problems.
