In short: Magnesium chloride is a salt made of magnesium and chloride that dissolves very easily in water. Comparison studies found it absorbed as well as organic forms, and clearly better than magnesium oxide. It tastes bitter, so it's best taken diluted or as a tablet with food. On the outside, you'll know it as magnesium oil and as bath flakes.
Key points
- Well absorbed: in studies, magnesium from chloride was absorbed as well as from lactate, aspartate or citrate, and clearly better than from oxide.
- Magnesium content: anhydrous magnesium chloride is 25.5% magnesium; the common form with crystal water (hexahydrate) is 12.0%.
- Bitter, but easy to dilute: dissolved in a large glass of water or juice and split across two meals, it's well tolerated.
- Many faces: nigari, magnesium oil and bath flakes are all magnesium chloride. For taking by mouth, only products sold as food are suitable.
- Stay within the limit: keep to no more than 250 mg of magnesium a day from supplements. Large amounts at once have a laxative effect.
Contents
- What is magnesium chloride?
- How much magnesium is in magnesium chloride?
- Is magnesium chloride well absorbed?
- What is magnesium chloride good for?
- Delbet cure, infections, hair: what's the evidence?
- Taste, tolerance and the laxative effect
- How do you take magnesium chloride?
- On the skin: flakes, magnesium oil and baths
- Magnesium chloride, citrate or glycinate?
- Frequently asked questions
- Limits of the research and all sources
What is magnesium chloride?
Magnesium chloride is a salt: one magnesium particle and two chloride particles. You'll know chloride from table salt, where it sits next to sodium. In magnesium chloride, it sits next to magnesium.
The salt draws water out of the air and dissolves in water instantly. In shops, it's usually sold as white flakes or crystals. These contain crystal water built firmly into the structure; chemists call this the hexahydrate (six waters per magnesium).1
It's extracted from seawater or from old salt deposits. One well-known form is nigari: the bitter liquid left over once table salt has been extracted from seawater. In Japan, nigari has long been used to curdle soy milk into tofu.2, 3
What the studies show: a Japanese survey of 17 nigari samples and 15 raw products sold as food additives found large differences. Only 5 of the 15 additive samples met the planned Japanese purity standard, though no sample showed notable heavy-metal contamination.2
Chloride also has its own, officially approved role in the body. Chloride contributes to normal digestion by production of hydrochloric acid in the stomach. This claim applies to chloride from sources other than table salt, so it also covers magnesium chloride.4
How much magnesium is in magnesium chloride?
That depends on the water content. Anhydrous magnesium chloride is 25.5% magnesium. The hexahydrate, meaning the usual flakes and crystals, is only 12.0%. The rest is chloride and crystal water.
These figures follow from the weight of the atoms (our calculation from the molar masses):1
| Form | Molar mass | Magnesium content | To get 250 mg of magnesium, you need |
|---|---|---|---|
| Magnesium chloride, anhydrous | 95.21 g/mol | 25.5% | around 0.98 g |
| Magnesium chloride hexahydrate (flakes, crystals) | 203.30 g/mol | 12.0% | around 2.1 g |
How we calculated it: magnesium weighs 24.305 units. 24.305 divided by 95.21 gives 25.5%, divided by 203.30 gives 12.0%.
On the label: check whether the figure is given for magnesium or for magnesium chloride. 1,000 mg of magnesium chloride hexahydrate delivers only around 120 mg of magnesium. If a hexahydrate product states clearly more than 12% magnesium, something's off with the figure, or some anhydrous salt has been mixed in.
With the magnesium, you always take in chloride too. 250 mg of magnesium as chloride comes with around 730 mg of chloride. That's just over 90% of the daily amount given as a reference value for chloride on food labels (800 mg).5 For comparison, the same amount of chloride is in around 1.2 g of table salt (our calculation).
Is magnesium chloride well absorbed?
Yes. Magnesium chloride is one of the well-absorbed forms, even though it isn't an "organic" form of magnesium. The reason is its solubility: in the stomach, the magnesium is already dissolved.
What the studies show: in a US study with healthy volunteers, magnesium from chloride, lactate and aspartate was absorbed equally well. From oxide, only around 4% got through.6 In a Norwegian study with 18 female students, the amount of magnesium in the urine rose just as much after a chloride solution as after citrate-lactate tablets.7 A 2025 review of controlled studies in healthy adults rates citrate and chloride as well absorbed, and oxide as poorly absorbed.8
A larger review of 14 comparison studies finds organic forms slightly ahead on average, and shows one thing above all: the bigger the single dose, the smaller the share that gets absorbed.9
The tablet matters. In one study, magnesium from enteric-coated chloride tablets was absorbed far worse than from a dissolved comparison form.10 The coating probably opens only late in the gut, leaving less time for absorption.
Our take: for absorption, magnesium chloride plays in the same league as citrate and glycinate. If the bitter taste doesn't bother you, or you take tablets, it's a good choice. You get the most out of it dissolved, or as an ordinary (non-enteric-coated) tablet, split into two smaller portions with food. How chloride and glycinate compare head to head is something studies still need to show.
What is magnesium chloride good for?
For everything magnesium is good for. The EU's officially approved claims apply to every form of magnesium, including chloride:
- Magnesium contributes to a reduction of tiredness and fatigue.
- Magnesium contributes to normal muscle function.
- Magnesium contributes to normal functioning of the nervous system.
- Magnesium contributes to electrolyte balance.
You'll find an overview of all ten claims in our article Magnesium benefits.
Magnesium chloride specifically has been studied a lot, because it's easy to dose as a solution. Most of the studies looked at people with low magnesium levels or certain health conditions.
What the studies show: a Mexican research group studied 116 adults with prediabetes and low magnesium levels. For four months, they drank 30 ml of a 5% magnesium chloride solution daily (382 mg of magnesium) or a placebo. With magnesium, blood magnesium levels rose, and fasting blood sugar ended up lower than in the placebo group.11 In a US study, 126 adults with mild to moderate depressive symptoms took 248 mg of magnesium as chloride daily for six weeks. Their symptoms, measured on a questionnaire, improved more than during the six weeks without magnesium.12 People with fibromyalgia, a chronic pain condition, reported less severe pain after a month on 100 mg of magnesium as chloride than on placebo.13
These studies describe what researchers observed in specific groups. They're not a substitute for treatment. If you have a medical condition, talk to your doctor about magnesium.
Delbet cure, infections, hair: what's the evidence?
Magnesium chloride is searched for especially often in France, Spain, Italy and Romania, where many people regard it as a home remedy. The "Delbet therapy" is named after the French surgeon Pierre Delbet. Guides and forums mention solutions for colds, joint complaints or grey hair.
Looked at factually: we haven't found any controlled human studies testing magnesium chloride for infections, hair or as a "cure". The solid studies on magnesium chloride are the ones described above, mostly in people with low magnesium levels. What you can say with confidence is in the official claims above.
If you want to try a "cure" from a recipe you found online, work out the amount of magnesium first. One example: 20 g of magnesium chloride hexahydrate in one litre delivers around 2.4 g of magnesium (our calculation). A 125 ml glass then contains around 300 mg, so more than the 250 mg upper limit for supplements.14
Taste, tolerance and the laxative effect
Magnesium chloride tastes distinctly bitter, with a slightly salty, metallic note. Well diluted, with juice, or as a tablet, the taste is much less noticeable.
What the studies show: in taste tests, magnesium chloride was described above all as bitter, and also as salty, metallic and astringent.15 In a small study, the stomach emptied more slowly after 800 mg of magnesium chloride.16
Like all readily soluble magnesium salts, magnesium chloride can soften stools in larger amounts. Magnesium the gut doesn't absorb holds onto water. In France, it's therefore also used for a "purge", a kind of bowel cleanse. We'd advise against this: a large single dose doesn't give you any extra magnesium; what it mostly gives you is diarrhoea.
What the studies show: the EU food safety authority sets the upper limit for magnesium from supplements at 250 mg a day, especially for readily soluble salts such as chloride.14 An analysis of newer studies found that amounts between 128 and 1,200 mg a day mostly caused no more diarrhoea than placebo.17 In the US study with 248 mg of magnesium as chloride a day, it was well tolerated.12
Important: with reduced kidney function, magnesium can build up in the body.18 In that case, only take magnesium chloride after talking to your doctor. Very large amounts, for example as a laxative or as undiluted nigari, can cause too much magnesium in the blood even in healthy people. Case reports describe heart rhythm problems and circulatory problems, in rare cases with a fatal outcome.3, 19, 20 Leave a gap of a few hours from thyroid hormone, certain antibiotics and osteoporosis medicines. The details are in When to take magnesium?
How do you take magnesium chloride?
Dissolve it in a large glass of water, or take it as a tablet, each with a meal. Stick to no more than 250 mg of magnesium a day from supplements, unless your doctor says otherwise. It's best to split the amount across two meals, since proportionally more is absorbed from smaller portions.9
How to do it:
- Powder or flakes (hexahydrate): for 125 mg of magnesium, you need around 1 g of salt. Dissolve it in at least 200 ml of water, ideally with a splash of juice against the bitter taste. One portion in the morning and one in the evening makes 250 mg (our calculation).
- Ready-made solutions and nigari: check the magnesium content per millilitre. Liquid nigari is very concentrated. In a Japanese study, 5 ml of nigari contained 500 mg of magnesium, double the daily upper limit in a single teaspoon.21
- Tablets: take ordinary tablets, not enteric-coated ones. In one study, far less was absorbed from these.10
- Only take food-grade products: bath flakes and magnesium oil aren't meant for drinking. Only take products labelled as a food supplement or food.
What the studies show: the Mexican studies used 382 mg of magnesium as a chloride solution a day, the US study on depressive symptoms used 248 mg.11, 12
On the skin: flakes, magnesium oil and baths
A large share of magnesium chloride doesn't end up in a glass, but in the bathtub or on your skin. Magnesium oil isn't actually oil, but a concentrated solution of magnesium chloride in water that feels oily on skin.22 Magnesium flakes (magnesium chloride flakes) are hexahydrate flakes for full and foot baths.
With flakes, you can make your own magnesium oil too: mix equal parts flakes and warm water until everything has dissolved. 100 g of flakes contains around 12 g of magnesium (our calculation).
A warm foot bath with flakes in the evening is a pleasant ritual. How much magnesium reaches you through the skin varies from person to person. What studies show about oil, spray and baths, how to use them, and what to watch for with sensitive skin, we've covered in detail in Magnesium oil, spray and bath.
Magnesium chloride, citrate or glycinate?
All three are among the well-absorbed forms. The difference lies mainly in taste, tolerance and what you use them for.
| Magnesium chloride | Magnesium citrate | Magnesium glycinate | |
|---|---|---|---|
| Magnesium content (our calculation)1 | 25.5% anhydrous, 12.0% as hexahydrate | 16.2% anhydrous | up to 14.1% |
| Absorption | good, like lactate and aspartate, better than oxide6, 8 | good, better than oxide8, 9 | good, better than oxide9 |
| Taste | bitter | sour | mild |
| Tolerance | laxative in larger amounts | laxative in larger amounts | considered gentle on the stomach |
| Typical form | solution, tablets, oil, bath flakes | powder, capsules | capsules, powder |
| Notable for | also usable externally, comes with chloride | standard form, well studied | popular for the evening |
Our take: magnesium chloride is a well-absorbed, versatile form. It suits you if you like taking magnesium as a drink, prefer tablets, or want to use it for baths too. If you have a sensitive stomach, or don't like the bitter taste, you're well served by magnesium glycinate or magnesium citrate. You'll find all forms compared in Which magnesium is best?
Frequently asked questions
What is magnesium chloride? A readily soluble salt of magnesium and chloride. It's extracted from seawater or salt deposits and used as a supplement, in tofu coagulants (nigari), and externally as magnesium oil or bath flakes.2, 3, 22
Is magnesium chloride good for you? Magnesium chloride is a well-absorbed source of magnesium.6, 8 Magnesium contributes to a reduction of tiredness and fatigue. Magnesium contributes to normal muscle function. It's important to stay within 250 mg of magnesium a day from supplements.14
Is magnesium chloride dangerous for your heart? Not at normal amounts. It only becomes dangerous at very large amounts, for example when magnesium salts are drunk as a laxative or as undiluted nigari, and with reduced kidney function. Then, too much magnesium in the blood can disturb your heart rhythm.3, 18, 19
Is nigari the same as magnesium chloride? Almost. Nigari consists mostly of magnesium chloride, but depending on how it's made, it can contain other salts too. Quality varies: in a Japanese survey, only 5 of 15 additive samples met the planned purity standard.2
Can I take bath flakes by mouth? No, only if they're explicitly sold as food or a food supplement. Bath products aren't made or tested as food.
Does magnesium chloride help with grey hair? We haven't found any human studies on this. There's no officially approved claim for magnesium and hair, either.
Limits of the research and all sources
The comparison studies on absorption are small, and mostly measure magnesium in urine after a few days or a single dose.6, 7 That says only so much about supply over months. In a lab experiment with gut cells, magnesium from chloride even passed through worse than from oxide or carbonate; this hasn't shown up in humans so far.23 In a study of 17 healthy people, everyone received a single dose of 300 mg of magnesium as chloride. Afterwards, free magnesium in the blood rose, but the total blood level and urine level didn't change measurably. The study was co-funded by companies from the industry.24
The studies on blood sugar, depressive symptoms and fibromyalgia each looked at specific groups, mostly with low magnesium levels. Whether the results carry over to healthy people is unclear.11–13 The study on depressive symptoms had no placebo group.12 In the fibromyalgia study, the main outcome, overall stress, didn't differ from placebo; one co-author worked for the manufacturer of the product.13 In 15 trained athletes without a deficiency, some endurance measures were even slightly worse after nine days of 600 mg of magnesium chloride a day than with placebo.25 For uses such as the Delbet cure, infections or hair, controlled human studies are lacking.
Show all 25 sources
| # | Study | Who was studied | Result | Strength of evidence |
|---|---|---|---|---|
| 1 | PubChem: Chloride 5360315, Chloride hexahydrate 24644, Citrate 6099959, Bisglycinate 84645 | Substance database | Molar masses 95.21 / 203.30 / 451.12 / 172.42 g/mol → 25.5 / 12.0 / 16.2 / 14.1% magnesium | Reference data |
| 2 | Ogimoto et al. 2006, Shokuhin Eiseigaku Zasshi | 17 nigari samples, 15 raw additive products | only 5 of 15 met the planned specification; no heavy-metal contamination | Laboratory analysis |
| 3 | Jung et al. 2015, J Emerg Trauma Shock | one patient after drinking bittern | too much magnesium in the blood, prolonged QT interval; nigari serves as a tofu coagulant | Case report |
| 4 | Regulation (EU) No 432/2012 | EU list of approved claims | chloride and magnesium: approved claims | Official |
| 5 | Regulation (EU) No 1169/2011, Annex XIII | Reference intakes for nutrition labelling | chloride 800 mg, magnesium 375 mg per day | Official |
| 6 | Firoz & Graber 2001, Magnes Res | healthy adults, around 250 mg of magnesium a day, 4 products | oxide around 4% absorption; chloride, lactate, aspartate equal and better | Small study |
| 7 | Bøhmer et al. 1990, Magnes Trace Elem | 18 female students, urine over 24 hours | no difference between chloride solution, citrate/lactate and hydroxide | Small study |
| 8 | Merschmann et al. 2025, Mol Nutr Food Res | controlled studies in healthy adults | citrate and chloride well absorbed, oxide poorly | Review |
| 9 | Pardo et al. 2021, Nutrition | 14 comparison studies | organic forms better on average; share falls with dose | Systematic review |
| 10 | Fine et al. 1991, J Clin Invest | healthy adults, rising amounts with meals | far less absorbed from enteric-coated magnesium chloride than from dissolved acetate | Basic research study |
| 11 | Guerrero-Romero et al. 2015, Diabetes Metab | 116 adults with prediabetes and low magnesium, 382 mg/day as a chloride solution, 4 months | magnesium level higher, fasting blood sugar lower than with placebo | Controlled study, disease group |
| 12 | Tarleton et al. 2017, PLoS One | 126 adults with mild to moderate depressive symptoms, 248 mg/day, 6 weeks | questionnaire scores markedly better than without magnesium; well tolerated | Open study without placebo, university-funded |
| 13 | Macian et al. 2022, Nutrients | people with fibromyalgia, 100 mg/day, 1 month | main outcome overall stress unchanged vs placebo; less stress in subgroup, less pain | Controlled study, co-author at the manufacturer |
| 14 | EFSA / SCF 2001 | Agency opinion | upper limit 250 mg/day for readily soluble magnesium salts from supplements | Official assessment |
| 15 | Lawless et al. 2003, Food Qual Prefer | taste tests with calcium and magnesium salts | chloride mainly bitter, also salty, metallic, astringent | Sensory study |
| 16 | Geboes et al. 2002, Aliment Pharmacol Ther | 11 healthy adults, 800 mg magnesium chloride | stomach empties more slowly, digestion of fat and protein unchanged | Small study |
| 17 | Costello et al. 2023, Adv Nutr | 10 studies since 1997 | mostly no more diarrhoea than placebo (128–1,200 mg/day) | Review with assessment |
| 18 | Rosner et al. 2023, Mayo Clin Proc | Review | build-up with reduced kidney function | Review |
| 19 | Bokhari et al. 2017, Am J Med Sci | one patient, magnesium laxative | fatal magnesium excess despite normal kidney function | Case report with literature review |
| 20 | Torikoshi-Hatano et al. 2013, J Forensic Sci | a 75-year-old woman | death from magnesium excess after magnesium chloride in milk as a home remedy | Case report |
| 21 | Kishimoto et al. 2010, Br J Nutr | 16 healthy men, 5 ml nigari (500 mg magnesium) with a high-fat meal | blood fats after the meal lower and delayed | Small controlled study |
| 22 | Werner et al. 2017, Trace Elem Electrolytes | Review | magnesium oil is a concentrated magnesium chloride solution, not an oil | Review |
| 23 | Kyselovič et al. 2021, Physiol Res | gut cells in the lab, 7 salts | chloride, citrate, sulfate passed through worse than carbonate, pidolate, oxide | Cell study |
| 24 | Zhan et al. 2020, Nutrients | 17 healthy adults, 300 mg of magnesium as chloride, single dose | free magnesium in the blood rose, total level and urine unchanged | Small controlled study, co-funded by companies |
| 25 | Bomar et al. 2025, Nutrients | 15 trained athletes, 2 × 300 mg magnesium chloride, 9 days | endurance measures slightly worse than placebo | Small controlled study |
Author: PRONESIUM Editorial Team · Last reviewed: 01/10/2026 · This article does not replace medical advice.
