Magnesium is one of the few supplements where the label genuinely matters more than the brand. Two products can both say "magnesium 400 mg" and deliver wildly different amounts of usable mineral. Magnesium is also one of the small number of supplement ingredients with approved UK health claims, so unlike most of the wellness aisle, the benefits here are legally established rather than implied. Here's a UK buyer's guide to reading the label properly, which form to pick, and what to avoid.
Key takeaways
- The form determines absorption. Magnesium oxide is cheap and poorly absorbed. Glycinate and citrate are far better tolerated.
- Elemental magnesium is the only number that counts. "1,000 mg magnesium citrate" delivers roughly 160 mg of actual magnesium.
- UK reference intake is 300 mg a day for men and 270 mg for women, and most of that should come from food.
- 250 mg is the EU upper limit for supplemental magnesium, separate from what you get in your diet. More is not better.
- Magnesium has approved health claims, including contributing to normal psychological function and to the reduction of tiredness and fatigue.
Why magnesium became the UK's default supplement
Magnesium is involved in more than 300 enzyme systems in the body, and UK national diet surveys have consistently found a meaningful proportion of adults, particularly teenage girls and younger women, falling below the reference intake. That combination made it an easy recommendation.
Three things pushed it into the mainstream:
- It has approved claims. Most wellness ingredients legally cannot say what they do. Magnesium can, which makes it one of the few honest "benefit" stories on the shelf.
- The sleep conversation. Because melatonin is prescription-only in the UK, magnesium became the default ingredient in British night-time formulas.
- Form education. Shoppers learned that oxide and glycinate aren't the same thing, and started reading labels. Our glycinate vs citrate vs oxide guide is our most-read article for exactly that reason.
What to look for on the label
1. Elemental magnesium, not compound weight
This is the single most misread number in the category. A magnesium compound is the mineral bound to something else, and only part of that total weight is magnesium itself:
- Magnesium oxide: around 60% elemental, but poorly absorbed, so the high percentage is misleading
- Magnesium citrate: around 16% elemental
- Magnesium glycinate (bisglycinate): around 14% elemental
- Magnesium L-threonate: around 8% elemental
A compliant UK label states elemental magnesium and its % NRV (nutrient reference value). If a product only shouts the compound weight on the front, turn it over.
2. The right form for your purpose
There's no universally best form, only trade-offs:
- Glycinate: bound to the amino acid glycine, gentle on the stomach, the usual choice for daily use
- Citrate: well absorbed, but has a mild laxative effect at higher doses
- Malate: often chosen by people who exercise regularly
- Oxide: cheapest, poorest absorption, mostly used as a filler to inflate the headline number
3. A dose that respects the upper limit
EFSA sets a tolerable upper intake of 250 mg per day for supplemental magnesium, separate from dietary intake. A supplement delivering 100 to 200 mg elemental magnesium sits sensibly within that. Products pushing 400 mg or more of supplemental elemental magnesium are exceeding the guidance, and the main practical result is usually digestive.
4. % NRV stated clearly
UK labels should show the % NRV, based on a reference of 375 mg. This lets you compare products in seconds without doing conversion maths.
5. What else is in the formula
Magnesium is often paired with vitamin B6, which also contributes to normal psychological function, or with botanicals. Pairing is fine, as long as every dose is declared. A named stack beats a vague "relax complex".
6. Third-party testing and a CoA
Minerals can carry heavy-metal contamination from their source material. Independent batch testing with a certificate of analysis available on request is the baseline quality signal.
What to avoid
Oxide-only products with a big front-of-pack number
"Magnesium 500 mg" from oxide looks impressive and absorbs poorly. It's the most common way the category misleads.
Mega-doses above the upper limit
Supplemental magnesium above 250 mg a day exceeds EFSA guidance. There's no benefit to overshooting, and the practical outcome is usually loose stools.
Proprietary blends
If the label says "magnesium complex 600 mg" without breaking down each form and its elemental content, you cannot evaluate it. Assume the cheap form dominates.
Compound weight dressed up as the dose
Watch for "1,500 mg magnesium bisglycinate" in large type with "210 mg elemental (56% NRV)" in tiny print. The second number is the real one.
Sugar-loaded night formulas
Some magnesium drinks and gummies carry 8 to 12 g of sugar per serving. Check the nutrition panel, particularly for anything taken before bed.
How Healthier Options fits in
We don't sell a standalone magnesium supplement, and we won't pretend otherwise to fit this article.
Magnesium is included in our Ashwagandha Gummies with Lion's Mane & Ginkgo Biloba as part of a 4,700 mg active serving:
- 200 mg Magnesium Glycinate, the better-tolerated form, sitting within the 250 mg supplemental upper limit
- Alongside 2,500 mg KSM-66 Ashwagandha, 1,000 mg Lion's Mane and 1,000 mg Ginkgo Biloba
- With Vitamin B6 and B12, which also contribute to normal psychological function
- Pectin-based, fully vegan, no added sugar, third-party tested with a CoA on request
If you specifically want a high-dose standalone magnesium, buy a dedicated one and use the checklist above. If you want magnesium as part of a broader daily routine, ours covers it at a sensible dose.
Who should consider a magnesium supplement?
- People whose diets are low in leafy greens, nuts, seeds, wholegrains and legumes, the main food sources
- Vegans and vegetarians tracking their intakes, see our guide for vegans
- People who exercise heavily, as magnesium contributes to normal muscle function and electrolyte balance
- Older adults, as absorption tends to decline with age
- Anyone told by a GP that their intake or levels are low
Who shouldn't take magnesium supplements
- People with kidney disease or reduced kidney function, without medical supervision, as impaired kidneys can't clear excess magnesium
- Anyone taking certain antibiotics, bisphosphonates or diuretics, as magnesium can affect absorption. Ask a pharmacist about timing
- People already taking a magnesium-containing antacid or laxative, to avoid doubling up
- Pregnant or breastfeeding women, without checking with a GP or midwife
- Children, without paediatric advice
How long until you notice anything?
If your intake was genuinely low, correcting it happens over weeks rather than days, and the effect depends entirely on your starting point. If your diet was already adequate, topping up may change very little, which is the honest answer most brands won't give you.
Magnesium is a nutrient, not a fast-acting compound. Consistency beats dose size. Our guide to building a supplement routine that sticks covers the habit side.
Common questions
Which magnesium is best overall?
For most people taking it daily, glycinate is the sensible default: well tolerated and gentle on digestion. Citrate is a good alternative if absorption is your priority and you tolerate it. Avoid oxide-only products. Full comparison in our magnesium forms guide.
How much magnesium should I take a day?
UK reference intake is 300 mg for men and 270 mg for women, ideally mostly from food. For supplements specifically, EFSA's upper limit is 250 mg a day on top of your diet, so most people don't need a high-dose product.
Should I take magnesium in the morning or at night?
There's no strong evidence that timing changes the outcome for a nutrient. Many people prefer evenings, but the consistency of taking it daily matters much more than the hour.
Can I take magnesium with other supplements?
Generally yes, and it's commonly paired with B vitamins. Check you're not doubling up if you take a multivitamin or a combination product that already contains magnesium, such as ours. Space it apart from certain antibiotics and iron supplements, and ask a pharmacist if you take regular medication.
Read next
- Magnesium for Sleep: Glycinate vs Citrate vs Oxide
- Best Supplements for Sleep UK 2026
- The Best Supplements for Vegans
Last reviewed and updated July 2026. We refresh our articles every 90 days with the latest UK supplement-safety guidance, new internal links to related research, and any updates to dosing or ingredient evidence. This article is general information, not medical advice. Speak to your GP or pharmacist if you take regular medication.
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