What to look for in magnesium tablets?

The format's own issues, why tablets are usually oxide and whether a tablet dissolves at all

What to look for in magnesium tablets is a question about a format before it is a question about a mineral, because the five reads that apply to any magnesium, the salt, the elemental figure, the arithmetic, the pence and the compliance line, apply to a tablet too, and the tablet adds problems of its own. Why tablets are usually oxide: a compressed tablet has a practical size limit of a gram or so before it becomes hard to swallow, and magnesium oxide at about 60% magnesium by weight fits a full 300 to 400mg dose in one tablet, while bisglycinate at 20% would need one and a half to two grams of compound, two or three large tablets, so the tablet format selects for the salt this section least recommends, poorly absorbed and most laxative, and a reader who wants a tablet for convenience usually buys oxide without knowing it, the ingredients list being the first read for that reason. Whether a tablet dissolves at all: a tablet must disintegrate in the gut to release its contents, and a tablet that is compressed too hard, coated too thickly or built with the wrong excipients can pass through partly or wholly intact, the supplement tablet quality literature's finding that disintegration failures are a real and measurable problem in the category, so a tablet's quality is not only what it contains but whether it lets go of it, a question a capsule never raises because a two-piece shell dissolves in the stomach within minutes, and a question a reader can test crudely by dropping a tablet in warm water and watching whether it breaks up within half an hour.

The size problem, the split line, the abandonment problem, when a capsule is the better format, and the format filed

The size problem: a good salt in tablet form is large or several, a bisglycinate or citrate tablet delivering a useful elemental dose being the size that stops people swallowing it, and a manufacturer's answer being either a thin dose per tablet with a direction to take four, or a switch to oxide, the buying-tablets page's trap of a 300mg-of-what figure on a tablet that is either compound or oxide. The split line: a tablet with a score line divides a dose, useful for a reader who wants 150mg twice for absorption or who is titrating down for the gut, and a tablet without one crumbles when cut, coated tablets especially, so a split line is worth looking for on any tablet meant to be divided. The abandonment problem: a tablet that carries a laxative salt at the guidance level, the magnesium 400 oxide tablet the shelf is full of, is the format most likely to give a new user the loose stools that make them stop in week one, so the tablet that looked convenient is the one that ends up in the drawer, the every-day pages' adherence finding in reverse. When a capsule is the better format: for a nightly habit, for a good salt at a useful dose, for a reader who splits or opens their dose, for a reader who cannot swallow large tablets, and for anyone who wants the contents released reliably, a two-piece HPMC or gelatin capsule dissolving in minutes, opening into yoghurt or a smoothie for the reader who cannot swallow it, and carrying bisglycinate at 300mg elemental over two, the format this site's worked example uses for those reasons. A tablet is the better format for one reader, the constipated reader who wants oxide's laxative effect and tolerates it, and a reasonable one for a reader who has checked the salt is not oxide, the tablet breaks up in water and the elemental figure is honest. The format filed: tablets are usually oxide, must disintegrate, are large or several in a good salt, need a split line to divide, and are the format most often abandoned, with the capsule avoiding all five and the worked example being that capsule, £19.99 for 90 days at 22p.

The verdict, five format problems and a capsule that has none of them

What to look for in magnesium tablets: the format's own five issues before the mineral's five reads, that tablets are usually oxide because only oxide fits a full dose in one, that a tablet must disintegrate to be absorbed and heavy compression or a thick coating can stop it, that a good salt in tablet form is large or several, that a split line is needed to divide a dose without crumbling, and that a tablet carrying a laxative salt at the guidance level is the format most likely to be abandoned in week one, with a two-piece capsule of bisglycinate avoiding all five and a tablet being the better format only for the constipated reader who wants oxide's effect. The capsule that avoids the five: Futuro Labs Magnesium Glycinate, bisglycinate in a vegan HPMC capsule that opens, 300mg elemental at 80% NRV over two, £19.99 for 90 days at 22p a day.

What to check on the label

Questions people also ask

Why are most magnesium tablets magnesium oxide?

Because a compressed tablet has a practical size limit of about a gram and oxide, at about 60% magnesium by weight, fits a full 300 to 400mg dose in one tablet, while bisglycinate at 20% would need two grams of compound, so the tablet format selects for the least absorbed and most laxative salt.

How do I know if a magnesium tablet will dissolve?

Drop one in a glass of warm water and watch whether it breaks up within half an hour; a tablet that stays intact is compressed too hard or coated too thickly and may pass through the gut partly unabsorbed, a measurable problem in the supplement tablet category.

Are magnesium tablets or capsules better?

Capsules for a nightly habit, a good salt at a useful dose, a reader who splits or opens their dose and anyone who wants the contents released reliably, since a two-piece shell dissolves in minutes; tablets suit a constipated reader who wants oxide's laxative effect and a reader who has checked the salt, the dissolution and the elemental figure.

Can I cut a magnesium tablet in half?

Only reliably along a score line: a scored tablet divides a dose cleanly for a reader who wants 150mg twice, while an unscored or coated tablet crumbles when cut, and a capsule is opened into food instead.

What is the best magnesium tablet for a lifter?

One that is not oxide unless constipation is the point, breaks up in warm water, prints an honest elemental figure and %NRV per tablet at a swallowable size, and carries a salt the gut tolerates so it is still being taken in month three; most lifters end up with a bisglycinate capsule for exactly those reasons.

Sources

1. The supplement tablet quality literature: compressed tablets must disintegrate in the gut to release their contents, and tablets that fail disintegration tests pass through unabsorbed, with coatings, compression force and excipient choice determining whether a tablet dissolves within the standard time. PubMed record
2. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research 2001;14(4):257-262. PubMed record
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. 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

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