We Tested 19 Magnesium in the UK — See Which One Is Best

What to Look for in Magnesium

The single most important decision when buying magnesium is the form of magnesium used, not the brand name or the capsule count on the front of the packet. Our analysis of 17 products found a clear pattern: the highest-scoring products all use chelated or organic-acid-bound forms of magnesium, while the lowest scorers (down to 53.0/100) tend to rely on magnesium oxide, a cheap form with poor bioavailability that passes through the gut largely unabsorbed.

Magnesium glycinate and bisglycinate are the gold standard for most people. The mineral is bound to the amino acid glycine, which improves absorption and is gentle on the stomach. Doctor's Best High Absorption Magnesium 100mg, the top-scorer at 82.0/100, uses magnesium glycinate and lysinate — both highly bioavailable chelated forms. Magnesium citrate is the next best option, bound to citric acid and well-absorbed, though slightly more likely to have a laxative effect at higher doses. Magnesium malate is worth considering for muscle fatigue and energy, while magnesium threonate is specifically researched for cognitive function and crosses the blood-brain barrier more effectively than other forms.

Dosage matters too. The UK recommended daily intake for adults is around 300mg for men and 270mg for women, though many people supplement with 200–400mg on top of dietary intake. Look at the elemental magnesium per serving, not the weight of the magnesium compound — a product labelled "Magnesium Bisglycinate 200mg" (like the Thorne option) means 200mg of the compound, which contains a lower amount of actual magnesium. Reputable brands state both figures clearly on the label.

Third-party testing is a meaningful quality signal. Only 4 of the 17 products we analysed carry independent verification (such as Informed Sport or NSF certification). If you're an athlete subject to drug testing, or simply want confidence that what's on the label matches what's in the capsule, prioritise products that have been independently tested.

Common Mistakes When Buying Magnesium

Our analysis of 17 products shows the average score is 71/100, but several products scored as low as 53.0/100 — meaning a significant portion of what's available is mediocre at best. The most common mistake is buying on price alone. The cheapest products in our dataset frequently use magnesium oxide, which is inexpensive to manufacture but poorly absorbed. You can end up spending less per bottle and getting almost no benefit.

Equally common is relying on Amazon star ratings. High review counts don't indicate ingredient quality. A product can have thousands of four-star reviews while still using a low-quality magnesium form with fillers and poor bioavailability. Our scoring takes ingredient quality and form into account — something Amazon reviews don't.

Many buyers also overlook the form entirely and chase the highest milligram number on the packet. A 500mg tablet of magnesium oxide will deliver far less usable magnesium to your cells than a 200mg capsule of magnesium glycinate. Bigger numbers do not mean better absorption or better results.

Another mistake is not considering what you actually need magnesium for. If you're taking it for sleep and relaxation, glycinate is consistently the preferred form. For constipation or digestion, citrate or oxide (in low doses) may actually be intentional. For muscle cramps and post-workout recovery, glycinate or malate are the more targeted choices. Buying a generic "magnesium" product without knowing the form is a common shortcut that leads to disappointment.

Finally, people underestimate the importance of cofactors. Some products combine magnesium with calcium, zinc, or vitamin B6 — the Solgar Calcium Magnesium plus Zinc, for instance, scores 74.0/100 at just £9.22. These combinations can be useful if you have multiple deficiencies, but calcium and magnesium compete for absorption when taken together in large amounts, so standalone magnesium may be preferable if you're specifically trying to address a deficiency.

Types and Forms Explained

Tablets are the most common format in our dataset, making up four of the 17 products analysed. Standard compressed tablets are affordable, easy to dose, and have a long shelf life. The trade-off is that some tablets use binders and fillers that may not suit people with food sensitivities, and they can be harder to swallow than capsules for some people.

Capsules — three products in our analysis — are generally preferred for higher-quality magnesium forms like glycinate and bisglycinate, where the powder filling needs to be well-measured and protected from moisture. Capsules tend to be cleaner in terms of additives, which is why many of the top-scoring products in this format attract vegans and those avoiding allergens.

Capsules with larger counts (often labelled simply as "Tablets" or "Capsules" across different branded formats) represent good value over time. Solgar's Magnesium Glycinate 400mg scores 80.0/100 and comes in at just £12.25, making it one of the more accessible premium options.

Sprays are a less common format — just one product in our dataset — and are applied directly to the skin rather than swallowed. Transdermal magnesium (usually magnesium chloride) is popular among athletes for post-exercise recovery because it can be applied directly to sore muscles. The evidence for transdermal absorption is less established than for oral supplementation, and spray products tend to offer less precise dosing. They work well as a complementary approach, particularly for localised muscle discomfort, but shouldn't be your primary source if you're addressing a genuine deficiency.

What to Expect to Pay

Prices in our dataset of 17 products range from £8.33 to £37.90, with an average of £16.51. The price range reflects genuine differences in quality, not just marketing — though there are exceptions at both ends.

At the lower end (under £12), you're generally looking at basic forms like magnesium oxide or combined mineral products. Solgar's Calcium Magnesium plus Zinc at £9.22 is a notable exception, scoring 74.0/100 for a combination formula — reasonable value if you need multiple minerals at once.

The £12–£20 range is where the best value sits. Solgar's Magnesium Glycinate 400mg at £12.25 (80.0/100) and Magnesium Citrate 60 Tablets at £12.00 (77.0/100) both offer high-quality chelated or organic-acid forms without a premium price tag. This is the sweet spot for most people.

Above £20, you're paying for premium chelated forms, larger pack sizes, or brand reputation. Doctor's Best High Absorption Magnesium 100mg at £26.40 is the top scorer overall at 82.0/100 and also the best value for money in the dataset with a VFM score of 78.0/100, meaning the quality justifies the price. The Thorne Magnesium Bisglycinate 200mg is listed without a current price, and its value for money score of 60.0/100 suggests it may run expensive when available.

Beyond £30, you're in territory where diminishing returns kick in. There is no product in our analysis that scores significantly higher than the £26.40 Doctor's Best option, so spending up to £37.90 isn't likely to get you meaningfully better results unless you have a specific form or certification requirement.