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Last updated: August 2026
Dosage Guide · UK · 2026
How Much Magnesium Glycinate Powder Per Day? The Number On The Tub Isn't The Answer
Every UK guideline for magnesium is written in elemental milligrams. Almost every magnesium product is sold by compound weight. Here is how to convert between the two, and what a sensible daily amount actually looks like in powder.
Quick Answer
Magnesium glycinate powder typically supplies between 14% and 20% elemental magnesium by weight, so 1g of powder provides roughly 140–200mg of actual magnesium. The GB Nutrient Reference Value is 375mg per day and the UK Expert Group on Vitamins and Minerals sets a guidance level of 400mg per day for supplemental magnesium. A common starting point is 1g of powder daily with food, adjusted from there. Always check the elemental percentage on the product you have bought, because it varies considerably between materials.
The Problem In One Sentence
Health guidance talks about elemental magnesium. Supplement labels usually talk about compound weight. They are not the same number, and the gap between them can be sevenfold.
Magnesium never exists on its own in a supplement. It is always bound to something — glycine, citrate, oxide, threonate. The compound weight is everything on the scale. The elemental weight is just the magnesium atoms inside it. When the NHS says adults need 270–300mg a day, it means elemental. When a tub says 1,000mg, it usually does not.
What Different Magnesium Forms Actually Deliver
| Form | Typical elemental magnesium | Powder needed for 300mg elemental |
|---|---|---|
| Magnesium oxide | ~60% | 0.5g |
| Magnesium glycinate (buffered) | ~18–20% | 1.5–1.7g |
| Magnesium citrate | ~16% | 1.9g |
| Magnesium glycinate (fully chelated) | ~14% | 2.1g |
| Magnesium L-threonate | ~8% | 3.8g |
Read that last column again. To get the same amount of magnesium you need roughly eight times as much threonate powder as oxide powder. Comparing two products on compound weight alone tells you almost nothing.
The Three UK Numbers Worth Knowing
270–300mg — NHS reference nutrient intake. 270mg a day for women, 300mg for men, from all sources including food. This is what your whole diet should provide, not what a supplement needs to.
375mg — the Nutrient Reference Value. The labelling benchmark. Every %NRV figure on a magnesium product is calculated against this.
400mg — the EVM guidance level. The UK Expert Group on Vitamins and Minerals guidance level for magnesium taken as a supplement, over and above food. Treat it as the ceiling rather than a target.
Those three get confused constantly. The NRV is a labelling convention, not a recommendation. The NHS figure includes your food. The EVM figure is the supplemental limit. A product delivering 48% NRV is not delivering "half of what you need" — it is delivering roughly 180mg on top of whatever your diet already provides.
Working Out Your Own Serving
Two steps, and you only need to do it once.
Step 1 — find the elemental percentage. It should be on the label or the product page. If it only says "magnesium glycinate 1000mg", that is compound weight and you need to ask the seller for the elemental figure. A seller who cannot tell you has not read their own specification.
Step 2 — divide your target by the percentage. Want 200mg elemental from an 18% powder? 200 ÷ 0.18 = 1,111mg, so a shade over 1g. Want 300mg from a 14% powder? 300 ÷ 0.14 = 2,143mg, so a little over 2g.
For the 18–20.3% material in our magnesium glycinate powder, the arithmetic comes out as:
| Target elemental | Powder | Approx. teaspoon | % NRV |
|---|---|---|---|
| ~100mg | 0.5g | ⅛ tsp | 24–27% |
| ~200mg | 1g | ¼ tsp | 48–54% |
| ~300mg | 1.5g | ⅜ tsp | 72–81% |
| ~400mg (EVM ceiling) | 2g | ½ tsp | 96–108% |
Why You Should Weigh It, Not Spoon It
Teaspoon conversions are everywhere in this category and they are all approximate, because powder density changes with how the material has settled, how humid the room is, and how heaped the spoon is. A "level" quarter teaspoon can vary by 30% between two people.
For a flavouring that would not matter. For a mineral where you are working to a guidance ceiling it does. A 0.1g resolution kitchen scale costs less than a single tub of powder and removes the guesswork permanently. Use the teaspoon figures as a fallback when you are away from home, not as your normal method.
Buffered Or Fully Chelated?
This is the distinction almost nobody explains, and it is why two products both called "magnesium glycinate" can assay 14% and 20%.
Magnesium glycinate is made by reacting magnesium oxide with the amino acid glycine. In a fully reacted chelate, essentially all the magnesium ends up bound to glycine, and the material assays around 14% elemental. In a buffered glycinate, a proportion stays as magnesium oxide, which pushes the elemental figure up to 18–20% because oxide is around 60% magnesium.
Buffered gives you more magnesium per gram, so less powder for the same intake and better value by weight.
Fully chelated is generally chosen for digestive comfort, because unreacted oxide is the component most associated with loose stools at higher intakes. Absorption of organic magnesium salts is generally reported as better than inorganic forms in the bioavailability literature (Schuchardt & Hahn, 2017).
Neither is better in the abstract. What matters is knowing which one you have — and a brand that publishes the composition rather than just the word "chelated" has told you.
Powder Or Capsules?
Powder wins on cost per gram and on control — you can take 0.7g if that is what suits you, which no capsule allows. Capsules win on convenience and on not needing scales or a drink. If you are new to magnesium and want to keep it simple, start with capsules. If you already know it agrees with you, or you are buying in volume, powder is the cheaper route by a considerable margin.
One practical note: magnesium glycinate powder has a mild, slightly alkaline taste rather than a bitter or sour one. Most people find it mixes into juice or squash without noticing it. Around 200ml of liquid per gram is about right.
What Magnesium Is Authorised To Say In The UK
Magnesium holds ten authorised claims on the GB Nutrition and Health Claims Register, more than almost any other mineral. A product must supply at least 15% NRV per portion to use them. Reproduced in their authorised wording:
- Magnesium contributes to a reduction of tiredness and fatigue
- Magnesium contributes to electrolyte balance
- Magnesium contributes to normal energy-yielding metabolism
- Magnesium contributes to normal functioning of the nervous system
- Magnesium contributes to normal muscle function
- Magnesium contributes to normal protein synthesis
- Magnesium contributes to normal psychological function
- Magnesium contributes to the maintenance of normal bones
- Magnesium contributes to the maintenance of normal teeth
- Magnesium has a role in the process of cell division
You will notice sleep is not on that list. Magnesium is marketed for sleep constantly, and there is no authorised claim for it. Any product or article telling you magnesium is a sleep aid is going beyond what the register permits.
When To Take It, And Who Should Check First
There is no required time of day. Take it with food, at a time you will remember, and keep it consistent — magnesium status responds to regular intake rather than to individual doses. If you are taking more than 1g of powder, split it across two meals rather than taking it all at once.
Speak to your GP before starting magnesium if you have reduced kidney function, since impaired kidneys cannot clear excess magnesium efficiently, or if you take prescribed medication — magnesium can affect absorption of certain antibiotics, bisphosphonates and thyroid medication, and separating doses by a few hours is often advised. Loose stools are the usual sign of taking more than suits you; reduce the serving and it resolves.
Dietary magnesium intake below reference levels is commonly reported among older adults across European populations (Barbagallo et al., 2021), which is part of why magnesium is one of the most widely supplemented minerals in the UK. That is a statement about intake data, not a suggestion that you personally are short of it — that is a question for a blood test and a GP, not a supplement label.
The Short Version
- Find the elemental percentage, not the compound weight.
- Divide your target elemental amount by that percentage to get your powder weight.
- Weigh it rather than spooning it.
- Start low, take it with food, stay consistent.
- Keep supplemental intake at or below 400mg elemental per day unless your GP says otherwise.
- If a label will not tell you the elemental figure, buy from someone whose will.
Where We Sit
Our Magnesium Glycinate Powder assays 18%–20.3% elemental magnesium by ICP, so 1g provides 180–203mg. It is a buffered glycinate — we publish the composition rather than leaving you to guess — milled to 40 mesh with no fillers, flow agents or additives. Eight sizes from 50g to 100kg, UK stock, same-day dispatch before 3:30pm.
If you would rather have a fixed serving, our magnesium glycinate capsules are the fully chelated form at 85mg elemental per capsule — a different material, generally chosen for digestive tolerance rather than magnesium per gram.
Frequently Asked Questions
How much magnesium glycinate powder should I take per day?
It depends on the elemental percentage of your powder. For an 18–20% material, 1g provides around 180–200mg elemental magnesium. Keep total supplemental intake at or below 400mg elemental daily, which is the UK EVM guidance level.
How many teaspoons is 1g of magnesium glycinate powder?
Roughly a quarter teaspoon, so half a teaspoon is about 2g. Treat these as approximate — powder density varies, and a scale is more accurate.
Is 400mg of magnesium too much?
400mg elemental is the UK Expert Group on Vitamins and Minerals guidance level for supplemental magnesium in adults. It is a ceiling rather than a target, and it does not include magnesium from food. Speak to your GP before exceeding it.
Why do two magnesium glycinate products show different elemental percentages?
Because one is likely a fully reacted chelate at around 14% and the other a buffered glycinate at 18–20%. Buffered material retains some magnesium as oxide, which raises the elemental figure.
Should I take magnesium in the morning or at night?
There is no required time. Take it with food at a time you will remember. Consistency matters more than timing.
Does magnesium help with sleep?
There is no authorised GB health claim for magnesium and sleep, so we cannot tell you it does. Magnesium does hold an authorised claim for contributing to normal psychological function, which is a different and narrower statement.
Can I take too much magnesium?
Loose stools are the usual first sign of taking more than suits you, and reducing the serving resolves it. People with reduced kidney function should not supplement magnesium without medical advice, because impaired kidneys cannot clear the excess efficiently.
Research References
Provided for educational context only. These are not health claims and do not describe the effects of any product.
Schuchardt JP, Hahn A. Intestinal Absorption and Factors Influencing Bioavailability of Magnesium — An Update. Current Nutrition & Food Science, 2017. Review. PubMed 29123461
Barbagallo M, Veronese N, Dominguez LJ. Magnesium in Aging, Health and Diseases. Nutrients, 2021. Review. PubMed 33652515
Rondanelli M, Faliva MA, Tartara A, et al. An update on magnesium and bone health. Biometals, 2021. Review. PubMed 33959846
Read our full magnesium guide on r/HealthByKnowledge →
Food supplement — not a medicine. This article is general information and not medical advice. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Do not exceed the recommended intake. Consult your GP before starting any supplement if you are pregnant, breastfeeding, taking prescribed medication, or have an existing medical condition — particularly reduced kidney function.
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