Swallowed, magnesium chloride is a good form. The hydrated salt is about 12% magnesium by formula weight against about 14% for bisglycinate, and the NIH Office of Dietary Supplements names chloride among the better-absorbed forms. Chloride is also the salt in topical magnesium oil, and there the case is weak: a 2017 review found too little evidence that magnesium applied to the body raises body magnesium to recommend it.
So this comparison splits in two. Taken by mouth, chloride and glycinate are both defensible daily forms with different trade-offs. Applied to the body, chloride is being sold on a route the evidence does not support, and that half of the question is where most of the confusion lives.
What is the difference between magnesium chloride and magnesium glycinate?
Chloride is an inorganic salt: one magnesium bound to two chloride ions, usually sold hydrated with six water molecules, which puts it at about 12% magnesium by formula weight. Glycinate holds one magnesium between two molecules of the amino acid glycine and is about 14% magnesium. Both dissolve in water. Chloride has a direct absorption record in small human studies, glycinate a thinner one, and only chloride is also sold for application to the body.
The "inorganic" label is worth a sentence, because it is the word the rest of the aisle uses against forms like chloride. Organic salts such as citrate, glycinate and malate are often sold as inherently better absorbed than inorganic ones. Chloride is the inorganic salt that breaks the rule: it dissolves readily, which is the property that matters, and the absorption studies below put it level with the organic salts rather than behind them.
Is magnesium chloride a good form of magnesium?
Swallowed, yes. The NIH Office of Dietary Supplements names chloride, with aspartate, citrate and lactate, as forms small studies found more completely absorbed than oxide and sulfate. In Firoz and Graber's study of four commercial products, oxide's fractional absorption was 4% while chloride, lactate and aspartate were significantly higher and equivalent to each other. The same Office also lists chloride among the forms most often reported to loosen stools.
The Firoz and Graber study (Magnesium Research, 2001) measured absorption the practical way, as the rise in urinary magnesium in normal volunteers given about 21 mEq of each product a day — roughly 255 mg of magnesium, by our arithmetic. Its conclusion is the useful one for anyone reading a label: an inorganic salt can be as bioavailable as an organic one, depending on the preparation. Its limits are the usual ones for this literature. Urinary excretion is a proxy for absorption rather than a direct measure, and the abstract does not report how many volunteers took part.
The European regulator files chloride the same way. The Scientific Committee on Food's upper level for supplemental magnesium, carried in EFSA's current overview, applies to "readily dissociable" magnesium salts, and chloride is the first example it names, ahead of sulphate, aspartate and lactate. Readily dissociable means the salt lets go of its magnesium easily in solution, which is the first step to absorbing it.
A recent trial in people who train points the same way. Bomar and colleagues (Nutrients, 2025) gave a magnesium chloride product to 15 regular exercisers for nine days in a double-blind crossover: ionised magnesium in the blood rose from 0.47 to 0.63 mmol/L by day eight (p = 0.015), so the chloride was absorbed. Performance did not improve, and two measures fell. The trial was funded by the company that supplied the product, it was 15 people for nine days, and what it found is set out in full in magnesium glycinate side effects.
How much elemental magnesium is in magnesium chloride?
About 12% of the hydrated salt by formula weight, and about 26% of the anhydrous salt. The difference is water of crystallisation: magnesium chloride hexahydrate carries six water molecules, and those six weigh more than the magnesium chloride they are attached to. The same elemental dose therefore takes roughly twice as much hexahydrate as anhydrous salt, which is why the elemental figure in the panel tells you the dose and the form name does not.
The reference amount in this table is 275 mg of magnesium, the elemental figure printed on Night Work's label. It is a label figure, and nothing in the table was measured; every compound weight is 275 divided by the unrounded magnesium fraction behind the percentage beside it, from PubChem's formula weights, rounded to the nearest 10 mg.
| Form | Magnesium by weight | Compound needed for 275 mg of magnesium |
|---|---|---|
| Magnesium chloride, hexahydrate | about 12% | about 2,300 mg |
| Magnesium chloride, anhydrous | about 26% | about 1,080 mg |
| Magnesium bisglycinate | about 14% | about 1,950 mg |
| Night Work, by its label | 11% (275 ÷ 2,500) | 2,500 mg of magnesium glycinate |
Two readings follow. As a capsule ingredient, hydrated chloride needs a little more powder than bisglycinate for the same magnesium, so neither makes for a small serving. And the hydrate question is a reason to trust the printed elemental figure over any table, including this one. The same division across every common form is in supplement forms compared, and the method, with the atomic masses printed, in how to read an elemental magnesium label.
Does magnesium chloride cause loose stools?
It can, at higher doses, like any magnesium salt. The NIH Office of Dietary Supplements lists chloride with carbonate, gluconate and oxide as the forms most commonly reported to cause loose stools, and attributes the laxative effect of magnesium salts to unabsorbed salt holding water in the bowel. Being well absorbed and appearing on that list are not a contradiction: whatever share of a dose is not absorbed acts on the bowel, so the dose decides.
That is the practical difference from glycinate, and it is a difference of reputation more than of measurement. Glycinate is the form usually chosen when a looser bowel is the effect someone wants least, but no trial we found has compared chloride with glycinate on gut effects at the same elemental dose. Glycinate's own absorption record is thin: in a 2024 crossover that gave 375 mg of magnesium as each of four forms, Pajuelo and colleagues saw no significant rise in plasma magnesium after bisglycinate, with a sponsor selling a competing ingredient and a six-hour window. The fuller comparison is in glycinate against citrate.
Does magnesium oil absorb?
There is little evidence that it raises the body's magnesium. Magnesium oil is magnesium chloride dissolved in water, sprayed or rubbed on. Grober and colleagues' 2017 review in Nutrients concluded that the promotion of transdermal magnesium is scientifically unsupported and that they could not yet recommend it. The body's outer layer is a water-repellent barrier, and a magnesium ion in solution is charged and surrounded by water, which is close to the worst profile for crossing it.
The review's reasoning is specific. A charged ion cannot dissolve its way through the fatty outer layer, so the only plausible routes are the follicles and sweat glands, which Grober and colleagues put at 0.1% to 1% of the body's surface area. The studies offered for the other side were few and, in their words, of "questionable quality."
The best of them is small. Kass and colleagues (PLoS One, 2017) randomised 25 adults to a magnesium cream supplying 56 mg of magnesium a day or a placebo cream for two weeks, applied to the torso and legs, and analysed 24. Serum magnesium in the cream group went from 0.82 to 0.89 mmol/L, a change that was not statistically significant (p = 0.29); urinary magnesium did not change significantly either (p = 0.48). The serum rise reached significance only in a subgroup of non-athletes. The authors reported no specific funding, and one of them declared a future royalty interest in a different magnesium cream. A pilot of 24 people, a subgroup finding and 56 mg a day — about 13% of the 420 mg RDA for men over 30 — is a reason for a larger trial, not a reason to buy a spray.
Can an Epsom salt bath raise your magnesium?
Not on any evidence that has passed peer review. Epsom salt is magnesium sulfate rather than chloride, and the study usually quoted for it — 19 people bathing daily for seven days, with a rise in plasma magnesium reported — was, in Grober and colleagues' account, published only on the internet and never in a peer-reviewed journal. Whatever a bath is for, it is not a measured way to take magnesium.
Sulfate is also one of the two forms the NIH Office of Dietary Supplements names as less well absorbed when swallowed, alongside oxide. A salt that is a weak performer by mouth is an odd candidate for a route with a barrier in the way.
Which is better, magnesium chloride or glycinate?
Swallowed, both are reasonable daily forms, and chloride has the firmer absorption record. As the usual hydrate it carries less magnesium per gram, about 12% against 14%, and it sits on the Office of Dietary Supplements' list of forms most often reported to loosen stools; glycinate is chosen for tolerability, on thinner evidence. Applied to the body as an oil or a cream, chloride has not been shown to raise body magnesium in any trial large enough to rely on.
Either way the arithmetic is the same: read the elemental figure, divide it by the compound weight, and add every supplemental source in the day against the 350 mg ceiling on supplemental magnesium, which counts supplements and medicines but not food. The ceiling and how a cabinet reaches it are in can you take too much magnesium; the daily requirement it sits against is in how much magnesium per day; the panel vocabulary is in the supplement label glossary; and the full buying procedure is in how to choose a magnesium supplement.
What the research does not show
No trial has compared magnesium chloride with magnesium glycinate in people. The chloride absorption evidence is a 2001 urinary-excretion study of four commercial products with an unreported number of volunteers, the Office of Dietary Supplements' summary of small studies, and a nine-day, 15-person crossover funded by the company that supplied its chloride product. That is enough to call chloride well absorbed by mouth. It is not enough to rank it against glycinate, and this page does not.
The topical evidence is thinner still. One randomised pilot of 24 analysed adults at 56 mg a day for two weeks, a significant finding only in a subgroup, a bath study that never reached a journal, and a review that weighs them and declines to recommend the route. No trial we found measured serum magnesium after weeks of a chloride spray. The absence of evidence is not proof that nothing crosses; it is a reason not to count a spray toward a daily intake.
Nor does any of this show chloride, sprayed or swallowed, doing anything a man who trains would notice beyond a blood figure. What magnesium does in the body belongs to the mineral, whichever salt carries it. Magnesium supports normal muscle function.* The evidence form by form is collected in the magnesium research summary, and the other comparisons in this series are glycinate against malate and glycinate against oxide.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Where Night Work sits
Night Work is magnesium glycinate in capsules: by its label, 275 mg of elemental magnesium from 2,500 mg of magnesium glycinate per three-capsule serving, 30 servings. It is the only supplemental magnesium in the TARE range, so the label's 275 mg is the whole of the range's supplemental total, 75 mg under the 350 mg tolerable upper intake level. TARE sells no chloride and no topical magnesium, so nothing above is an argument for something on our shelf. What is and is not measured for Night Work is set out on Testing & Certification.
Sources
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals (updated 6 January 2026). NIH Office of Dietary Supplements
- Firoz M, Graber M. Magnes Res 2001;14(4):257-262. PubMed 11794633
- Grober U, Werner T, Vormann J, Kisters K. Nutrients 2017;9(8):813. PubMed 28788060
- Kass L, Rosanoff A, Tanner A, et al. PLoS One 2017;12(4):e0174817. PubMed 28403154
- Bomar MC, Ewell TR, Brown RL, et al. Nutrients 2025;17(5):915. PubMed 40077784
- PubChem. Magnesium chloride hexahydrate, CID 24644 (molecular formula Cl2H12MgO6). pubchem.ncbi.nlm.nih.gov
- PubChem. Magnesium chloride, CID 5360315 (molecular formula Cl2Mg). pubchem.ncbi.nlm.nih.gov
- Pajuelo D, Meissner JM, Negra T, et al. Nutrients 2024;16(24):4367. PubMed 39770988
- European Food Safety Authority. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food and the EFSA NDA Panel, version 11 (August 2025). efsa.europa.eu