Minerals & forms

Magnesium citrate vs oxide: which is in your electrolytes?

The same milligram number on two labels can behave very differently, because the form of magnesium decides how much your body actually takes in and whether it upsets your stomach.

Rawstone Learn · general education, not medical advice

Magnesium is a mineral your body needs, and you lose some of it in sweat. So it turns up on the label of most electrolyte drinks and supplement tubs. What almost nobody explains is that "magnesium" on a label is not one single thing. It is always bound to something else to make a stable powder, and that partner changes everything about how the magnesium behaves. The two you will see most often are magnesium oxide and magnesium citrate. They are not interchangeable.

What "form" actually means

Pure magnesium is a metal, so it is never sold on its own in a drink. It is joined to another compound to make a usable powder. That partner is the "form". Magnesium oxide is magnesium joined to oxygen. Magnesium citrate is magnesium joined to citric acid, the mild sour compound found in lemons. Same magnesium at the centre, very different behaviour once it hits water and then your gut.

Magnesium oxide: high on the label, low on absorption

Oxide is a common form, and there is a practical reason it turns up so often. Gram for gram it carries a lot of magnesium and it is inexpensive, so it is an easy way to reach a high number on the label. The thing worth understanding is absorption, which just means how much of it actually crosses from your gut into your body rather than passing straight through. Oxide is one of the lower forms for this, so your gut takes in only a small fraction of it.

Oxide also barely dissolves in water. Drop it in a glass and much of it sits there as a cloudy grit rather than going into solution. That is a problem for a drink, where you want the mineral evenly mixed and ready to absorb.

The loose-stool effect, explained plainly

Here is the bit people search for most: does magnesium cause diarrhoea? It can, and the form is a big part of why. Any magnesium your gut does not absorb stays in your bowel, and magnesium left in the bowel pulls water in alongside it. More water in the bowel means looser stools. That is not a mysterious side effect, it is the same principle behind some magnesium laxatives.

Because oxide is so poorly absorbed, more of it is left behind to do exactly that, especially at higher doses. Citrate is absorbed more readily, so less is left over, though any magnesium can loosen things if you take enough. The practical point is that the small amount in an electrolyte serve, like the 75mg in Rawstone, sits well below the level where this normally becomes an issue.

Magnesium citrate: dissolves fully, absorbs better

Citrate is the form we chose, and the reason is straightforward. It dissolves fully in water, so it actually belongs in a drink, and studies of how well different forms are taken up put citrate well ahead of oxide. There is a bonus for a powdered electrolyte too. The citrate part is mildly sour, so it works with the citric flavour of the drink instead of fighting it, and it does not carry the metallic or chalky edge that cheaper forms can bring. You can read more about how mineral forms shape taste and absorption in the science of salt and hydration.

The honest bit about cramps

Magnesium is often linked with muscle cramps, so it is worth being straight about the evidence. A large 2020 review by the Cochrane group, which pools together many trials to get a clearer answer, looked at eleven studies and concluded it is unlikely that magnesium supplements give any clinically meaningful protection against cramps. We are not going to tell you Rawstone stops cramps, because the research does not support it. Magnesium is on our label because it is a mineral you genuinely lose in sweat and it rounds out a complete electrolyte, not as a muscle-cramp fix.

Where Rawstone sits

Rawstone is a sugar-free electrolyte hydration powder, and it carries 75mg of magnesium per serve, as magnesium citrate. Under Australian food labelling rules that amount makes it a source of magnesium, which is a sensible everyday top-up rather than a mega-dose. We picked citrate over oxide on purpose: it dissolves cleanly, more of it is absorbed, and it keeps the drink tasting like a drink. It sits alongside 1000mg of sodium and 250mg of potassium, and the potassium is also a citrate for the same taste and absorption reasons. If you want the wider picture on daily use, our piece on electrolytes while fasting covers when a lighter serve makes sense.

This article is general education about minerals and physiology, not medical advice. Rawstone is a food supplement, not a medicine, and is not intended to diagnose, treat, cure or prevent any disease. If you have a kidney condition or take medication that affects your magnesium levels, talk to your doctor before using any electrolyte or magnesium supplement.