Magnesium: the types on the shelf and how they differ

Walk along a supplement shelf and magnesium appears half a dozen times with a different second word each time. Those second words are not marketing: magnesium is a reactive metal, so it is always supplied bound to something — an acid, an amino acid, or oxygen. That partner determines the size of the tablet, how the product tends to be tolerated, and crucially how much actual magnesium is in a serving.

Start with the elemental figure

The number that matters is elemental magnesium — the magnesium itself, not the weight of the whole compound. A capsule containing 500 mg of magnesium citrate does not contain 500 mg of magnesium; the citrate makes up most of that weight. Well-written labels state it plainly, for example 'magnesium citrate 1500 mg, providing 240 mg magnesium'.

If a label only shows the compound weight, you cannot compare it fairly with a label that shows elemental content. In the EU and UK the elemental figure and the %NRV must appear; in North America the Supplement Facts panel shows magnesium with a %DV. Either way, that is the line to read.

The forms you will see

The list below is descriptive, not a ranking. Different forms suit different people, and the most common reason someone switches is digestive comfort rather than any dramatic difference in outcome.

Magnesium oxide is a useful example of why the elemental figure matters in both directions. It carries a high proportion of magnesium by weight, which keeps tablets small, but a smaller share of it is absorbed than from forms such as citrate or glycinate. Neither fact alone makes it the right or wrong choice — it depends on the dose, the format and how it sits with you.

Food first, as usual

Magnesium is widespread in food: pumpkin seeds, almonds, cashews, dark leafy greens, legumes, wholegrains and dark chocolate all contribute. Most national guidance treats a varied diet as the starting point and supplements as a way of closing a gap, not a replacement for the list above.

• Read the elemental magnesium per serving, not the compound weight.
• Note how many capsules make up that serving.
• Powders let you divide a dose; capsules are easier to travel with.
• If a product does not agree with you, a different form is often the simplest change.

Sensible cautions

Magnesium supplements can interact with certain medicines, including some antibiotics, and intakes above published upper limits can cause digestive upset. Anyone with reduced kidney function, or who is pregnant, breastfeeding or taking prescription medicines, should ask a pharmacist or doctor before starting. This article is educational and is not a substitute for that conversation.

The bottom line

There is no single best magnesium. Compare on elemental content, pick a form and format you can keep taking comfortably, and keep the rest of your diet in the picture. If you are choosing between two products that look identical, the label — not the front of the box — will tell you which is which.

This article is educational. Food supplements are not a substitute for a varied diet or medical care. Speak to a healthcare professional about your own situation.