How to read a magnesium supplement label?

Stop one: the ingredients line, where the form lives

Skip the front of pack entirely and start at the ingredients, listed by weight, heaviest first. The first entry names the form, which is the single most consequential word on the bottle: magnesium bisglycinate first is a glycinate; magnesium oxide first is an oxide whatever the title claims; a blend of three forms with no split is oxide-heavy by construction. A percentage after the form, bisglycinate 20% on the exhibit, is a gift, because it lets you audit the maths at stop two. The rest of the line is excipients: a capsule shell, HPMC if vegan, gelatin if not, and processing agents in milligram amounts. Short lists are good signs; herb dustings and sweeteners are decisions someone made for you.

Stop two: the elemental line with %NRV, where the dose lives

The nutrition panel must state the nutrient per serving, and for magnesium that means the elemental amount with its percentage of the 375mg reference value. This line is the dose, full stop: 300mg at 80% NRV is a full serving, 56mg at 15% is the minimum that can even carry the authorised claims, and a missing line or missing percentage means the big number elsewhere was compound weight. Run the audit the percentage enables: compound weight times the form's percentage should equal the elemental line, and on the exhibit 1500mg at 20% checks out to the printed 300mg. Any label failing that multiplication has told you everything.

Stops three and four: the serving size, and the warnings

Stop three is the serving size, the quiet number that reprices everything: 2 capsules on the exhibit, meaning a 180 bottle is 90 days, and price per day is price over servings, never over capsules. Per-capsule statements get multiplied up before comparing anything. Stop four is the warnings block, worth reading once properly: the statutory lines, not a substitute for a varied diet, do not exceed the stated dose, keep from children, plus the one that matters most, consult a healthcare professional if on medication, pregnant or breastfeeding, which this site repeats because magnesium can shift the absorption timing of some medicines and a pharmacist answers the spacing question in a minute. A label missing the statutory lines is a label outside the rules.

Stop five: the address and the panel, where accountability lives

UK law requires the responsible company's name and address on the label; a brand hiding behind a logo and a web form has failed the cheapest test of accountability there is. The test panel is the voluntary stop that separates tiers: UK supplements are foods, checked by no regulator before sale, so a shown third-party heavy-metal and microbiology panel is the only pre-purchase evidence of what a batch contains, and the words lab tested without a visible panel are decoration. The exhibit shows both panels passed. Practise the five stops on the exhibit, Futuro Labs Magnesium Glycinate, 300mg elemental at 80% NRV, 2 capsules, vegan, UK made under GMP and BRC, £19.99 for 180 at 22p a day, and then on any shelf: how to read a magnesium supplement label is a thirty-second habit, and every trick this site catalogues fails at one of the five stops.

What to check on the label

Questions people also ask

What should I look for first on a magnesium label?

The ingredients line: the first-listed form decides more than anything else on the bottle. Bisglycinate first is the pattern to want.

How do I know the real magnesium dose on a label?

The elemental line with %NRV: 300mg at 80% is a full serving. If it is missing, the big front number is compound weight.

What does the percentage after magnesium bisglycinate mean?

The material's magnesium content by weight: 1500mg at 20% contains the 300mg elemental the panel states. It lets you audit the label's maths.

Are the warnings on supplement labels legally required?

The core lines are: varied-diet, stated-dose, keep-from-children. Their absence marks a label operating outside the rules.

Why does third-party testing matter on the label?

UK supplements are foods with no pre-market testing; a shown heavy-metal and microbiology panel is the only evidence of what a batch contains.

Sources

1. Futuro Labs Magnesium Glycinate listing, Amazon UK, label and price checked 31 August 2026. https://www.amazon.co.uk/dp/B0BT7Z5VQW
2. The Food Supplements (England) Regulations 2003 (food supplements are regulated as foods in the UK). https://www.legislation.gov.uk/uksi/2003/1387/contents/made
3. Retained Regulation (EU) No 1169/2011, Annex XIII: nutrient reference value for magnesium 375mg. https://www.legislation.gov.uk/eur/2011/1169/annex/XIII
4. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research 2001;14(4):257-262. PubMed record
5. Genuis SJ, Schwalfenberg G, Siy AK, Rodushkin I. Toxic element contamination of natural health products and pharmaceutical preparations. PLoS One 2012;7(11):e49676. PubMed record
6. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of health claims related to magnesium. EFSA Journal 2010;8(10):1807. https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2010.1807

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