Magnesium chloride: complete pharmaceutical guide (2026)
Magnesium chloride is the salt with the longest tradition in oral supplementation in Spain and the poorest digestive tolerance among the salts with useful bioavailability. Popularised by Ana María Lajusticia from the 1970s onwards, it was for decades the standard pharmacy magnesium until better-tolerated salts such as bisglycinate and citrate arrived. It is still a valid option in people who tolerate it, but most stop treatment because of diarrhoea or abdominal discomfort. This guide explains what it is, what it is used for, dosing, alternatives, and when continuing with it still makes sense.
This article is part of the master guide to the 10 types of magnesium. Here I go into detail on magnesium chloride.
What is magnesium chloride
Magnesium chloride (MgCl₂) is an inorganic salt of elemental magnesium with two chloride ions. Highly soluble in water, it comes as crystals, compacted tablets or sachets. Traditionally it has been credited with alkalising and restorative properties, more due to historic popular science messaging than to rigorous clinical evidence.
The origin of oral use in Spain
Ana María Lajusticia popularised magnesium chloride from the 1970s for joint problems, fatigue and energy. Entire generations associate it with the word "magnesium" without realising it is just one of more than ten available salts. This cultural inertia explains why it remains in high demand despite being overtaken by more modern forms.
Oral magnesium chloride vs topical magnesium chloride
The topical route (baths, sprays) has a genuine niche for local muscle relaxation without digestive issues. The oral route is where problems arise and is the main focus of this guide.
Bioavailability and tolerance of oral magnesium chloride
The oral bioavailability of magnesium chloride is medium–high (better than oxide, worse than bisglycinate or citrate). The issue is not absorption but tolerance: magnesium chloride causes diarrhoea, abdominal pain or heartburn in many people during the first 1–2 weeks at therapeutic doses. Many patients stop before giving it a fair trial.
What is magnesium chloride used for
- Traditional joint support: classic indication in early osteoarthritis and morning stiffness. Pharmacologically reasonable, but citrate or bisglycinate provide the same magnesium with better tolerance.
- Fatigue and general "tonic" use: magnesium itself works; for modern restorative use, bisglycinate and malate are usually a better choice.
- Occasional constipation: marked laxative effect at higher doses. Useful as an occasional laxative, not as long-term therapy.
- Topical use: foot or full-body baths, sprays. Real niche in muscle overload, post-exercise recovery and tension-related insomnia, without passing through the digestive tract.
Correct dose of magnesium chloride
Dosing is counted as elemental magnesium. Magnesium chloride provides around 12% elemental magnesium by total weight: a level teaspoon (~3 g) gives ~350 mg.
- Typical oral dose: 300–450 mg elemental magnesium per day, after the main meal.
- Classic Lajusticia regimen: 1 level teaspoon dissolved in water after dinner.
- Compacted tablets: 3–6 per day split into 2–3 doses, depending on brand.
- Starting off: begin with 1/4 of the target dose for the first 3–5 days to assess tolerance. If diarrhoea appears, reduce or switch to another form.
- Topical: 200–300 g in a full bath or 100 g in a foot bath for 15–20 minutes.
Ana María Lajusticia Magnesium Chloride 400 g: the classic reference
If you decide to try oral magnesium chloride, Ana María Lajusticia Magnesium Chloride 400 g is the historic reference product with the longest track record of use in Spain. Crystal format to dissolve in water, very competitive cost per dose and clear traceability. For those who tolerate it and keep up the habit it remains a valid and economical option; if you are trying it for the first time, it is wiser to start with a low dose before committing to a large tub.
Plantis Magnesium Chloride 100 Tablets: tablet format
If you prefer tablets to powder, Plantis Magnesium Chloride 100 Tablets is a convenient alternative: more controllable dose per unit and no bitter taste. It has the same tolerance profile as powder at equivalent doses.
Magnesium chloride vs bisglycinate: key comparison
- Where magnesium chloride wins: tradition, very low cost and topical use.
- Where bisglycinate wins: digestive tolerance, bioavailability, profile for sleep/anxiety support and long-term adherence.
For sustained oral use, bisglycinate clearly outperforms magnesium chloride. Magnesium chloride remains appropriate if you already tolerate it well or for topical use. For new users, I usually suggest starting with bisglycinate: see my magnesium bisglycinate guide.
Magnesium chloride vs citrate: when I prefer citrate
Citrate shares high bioavailability and some laxative effect with magnesium chloride but offers better digestive tolerance, a broader therapeutic profile (muscle function, bowel regularity, kidney stone prevention), improved taste and flexible formats. If your main goal was bowel regularity or muscle function, citrate is the logical update: see my magnesium citrate guide.
Vittalogy Triple Magnesium: modern all-round option
If you have been using magnesium chloride for years and want to update without giving up daily long-term magnesium supplementation, Vittalogy Triple Magnesium Complex combines bisglycinate + citrate + malate: broader functional coverage (sleep support, muscle function, cellular energy), far superior digestive tolerance and an easy capsule format. It is what I most often recommend when someone says "I have been on Lajusticia for years but I would like something better".
When NOT to take magnesium chloride
- Chronic diarrhoea or IBS with a tendency to loose stools.
- Severe renal impairment.
- Poorly controlled hypertension (caution because of extra chloride intake).
- Known gastric sensitivity (chronic heartburn, gastritis).
- Concomitant use with bisphosphonates, quinolones or tetracyclines: separate by at least 2 hours.
When to expect results with magnesium chloride
- Laxative effect: within 12–24 hours if the dose is sufficient.
- Joint support or general restorative effect: 4–8 weeks.
- Muscle function and energy: 4–6 weeks if well tolerated.
Common mistakes with magnesium chloride
- Starting at full dose on day one: main reason people give up. Titrate up from 1/4 dose.
- Taking it on an empty stomach: triggers heartburn and diarrhoea. Always take with food.
- Combining it with strong coffee or acidic drinks at the same time: increases discomfort. Separate doses.
- Persisting despite poor tolerance: if it bothers you, change salt form. A supplement you abandon does not work.
Frequently asked questions about magnesium chloride
Does magnesium chloride cure osteoarthritis? No supplement cures osteoarthritis. Magnesium supports protein synthesis and periarticular muscle function. It complements medical management; it does not replace it.
Why does it cause diarrhoea? Unabsorbed magnesium chloride draws water into the colon by an osmotic effect. The intensity depends on dose, baseline gut status and individual tolerance.
How many Lajusticia tablets can I take per day? The classic regimen is 1 level teaspoon of crystals after dinner (~350 mg elemental magnesium). With tablets, typical dosing is 3–6 per day depending on brand. Always start low.
Is magnesium chloride better than bisglycinate? Bisglycinate wins on tolerance, sleep/anxiety profile and adherence. Magnesium chloride keeps its niche in topical use and in people who already tolerate it well. For new users I favour bisglycinate.
Does magnesium chloride help you lose weight? Not directly. It may help normalise bowel movements and support muscle function but it is not a fat burner. Claims of dramatic weight loss are marketing without solid backing.
Final pharmaceutical recommendations
Magnesium chloride is the historic salt in Spain; it still has its place, but today there are forms with a better overall profile for most goals.
If you have been taking Ana María Lajusticia Magnesium Chloride for years and tolerate it well, I would not change: adherence is the most important factor in long-term supplementation. For topical use its usefulness is not in doubt.
If you are trying magnesium for the first time, consider a modern form: Vittalogy Triple Magnesium Complex covers more indications with better tolerance. If your main goal is sleep support or anxiety relief, my bisglycinate guide will be more relevant; if your focus is muscle function or digestion, see my citrate guide.
If you are unsure about your specific case or how to switch from magnesium chloride to a modern salt while keeping your daily regimen stable, you can contact our pharmacy team without obligation.
Magnesium chloride vs other forms of magnesium: quick comparison
| Form | Absorption | GI tolerance | Recommended use | Relative price |
|---|---|---|---|---|
| Magnesium chloride | Medium–high | Low (diarrhoea frequent) | Topical use and those who already tolerate it | € |
| Bisglycinate | High | Very high | Sleep support, anxiety, sustained use | €€€ |
| Citrate | High | Medium (laxative at high doses) | Muscle function, transit | €€ |
| Malate | High | High | Energy, chronic fatigue | €€ |
| Oxide | Very low | Low | Low cost; little clinical usefulness | € |
Frequently asked questions
Scientific references
