Magnesium Complex: 13 Supplements Compared

A magnesium complex is only better than a magnesium with a single form if the label says how much magnesium comes from which form, and most labels don't. We compared 13 widely sold supplements from drugstores, pharmacies and online retailers and did the math. All four complexes contain magnesium oxide, the cheapest form, and only one of them says how much magnesium comes from it. Six others are made entirely of oxide, including the most expensive of the 13.

What magnesium is good for and how much you need is covered in our magnesium guide. Here we're just looking inside the packages.

What is a magnesium complex?

A magnesium complex is a supplement that mixes several magnesium compounds in one capsule or tablet, for example oxide, citrate and bisglycinate. There's no fixed definition for the term, so each manufacturer decides for themselves how many forms go in and in what ratio.

The different forms exist because pure magnesium can't be put into a capsule. It always needs a binding partner, and that partner determines how much space the whole thing takes up and how well it dissolves in the gut. For oxide that's oxygen, for citrate it's citric acid and for bisglycinate it's the amino acid glycine.

Magnesium oxide is about 60% magnesium, while citrate and bisglycinate, depending on the variant, are only 12 to 16%. So for the same amount of magnesium, you need roughly four to five times as much citrate as oxide. That makes oxide small, light and cheap, and anyone who wants to print "400 mg" on an inexpensive tablet can hardly get around it. So the fact that oxide is in so many packages definitely has nothing to do with what your body makes of it, and everything to do with the purchase price of the raw material. It's no coincidence that all three drugstore products in our comparison were pure oxide. How exactly this converts is explained in our comparison of magnesium forms.

Magnesium complex comparison: the results

Half of the 13 supplements cost no more than €0.17 a day, the cheapest €0.05. Only three manage entirely without oxide: an effervescent tablet with citrate, a licensed medicine and a capsule with bisglycinate, and they cost between €0.24 and €0.41 a day. For comparison, the last row of the table shows our own magnesium, CALM by Fifty Five.

And this is where it gets really interesting. The most expensive of the 13 supplements comes from a pharmacy and is pure magnesium oxide. It costs €0.43 a day, more than eight times the cheapest drugstore tablet. Yet both contain exactly the same compound. So you can't tell the form from the price, only from the label.

How we compared

We copied price, ingredients and recommended daily intake from labels, product pages and one official product information sheet on September 24, 2026. No lab was involved. The selection ranges from the own brands of two drugstore chains through pharmacy brands and a licensed medicine to five well-known brands sold online. We don't name brands, because what we care about here is forms and numbers. For one of the two drugstore own brands, the magnesium content comes from the product name and a nutrition database, so the table is a little less solid at that point.

How do you recognize a good magnesium supplement?

You recognize a good magnesium supplement by its label. It states the form and amount, isn't mostly oxide and stays at no more than 250 mg of magnesium a day. We want you to be able to judge this yourself from now on, and five quick checks are all it takes. That's less than two minutes.

1. Magnesium per day. The nutrition table shows how much magnesium the daily serving delivers. Only this number can be compared, because the weight of the whole compound is always much higher.
2. The compound. Whether it's oxide, citrate, bisglycinate or carbonate is listed in the ingredients.
3. For complexes, the shares. A good label says how much magnesium comes from which form. If that's missing, stay skeptical.
4. The amount. If a supplement delivers more than 250 mg a day, it's above the upper limit. And if everything is in a single tablet, you can't even take less.
5. The rest of the list. The shorter it runs after the magnesium, the easier the product is to assess. In our comparison, it included hydrogenated fats, talc and sweeteners, among other things.

Is a magnesium complex worth it, or is one form enough?

A mix makes sense when every form in it has a job and the label states the shares. More forms alone don't make a supplement better, and a magnesium with just one well-chosen form is not an inferior product.

The best-documented gap is the one between citrate and oxide. In a double-blind study with 46 adults over 60 days, citrate produced the highest magnesium levels in the blood, a form bound to amino acids was also absorbed better than oxide, and oxide did no better than the placebo. The study was small, but it doesn't stand alone. When four commercial supplements were tested on healthy volunteers, only about 4% of the magnesium oxide was absorbed.

Whatever isn't absorbed stays in the gut and draws water in there, which is why very high doses of magnesium oxide have even been studied as a laxative in patients with chronic constipation. Ben from our story experienced exactly that with a cheap year's supply of 400 mg magnesium oxide, as you can read in Ben's story from shift work.

Bisglycinate is considered the form that's easiest on the stomach, and the first data on it do point that way. So far, though, it has only been studied on a small scale. The most frequently cited study involved twelve patients after bowel surgery and a single dose, and what came out of it is covered in our forms comparison under magnesium bisglycinate. Nobody has compared it over several weeks in healthy people yet.

Triple, 5-in-1, 7-in-1 or 8-in-1 complex: what does the number on the package mean?

The number tells you how many forms a supplement contains, but not how much magnesium each of them delivers. We didn't have a complex with seven or eight forms in our comparison, ours had three or five, but the math stays the same.

One of the complexes at least states the weight of each compound: 400 mg of oxide per day and 300 mg each of four other forms. That sounds like a fair split, but oxide carries a lot more magnesium and alone delivers a good 240 of the 400 mg, leaving around 40 mg for each of the other four. Five names are printed the same size on the package, and one of them delivers about six times as much as each of the others.

If there's no amount stated at all, only the ingredient list helps, because it's sorted by weight. In three of our four complexes, magnesium oxide comes first. In the fourth it's citrate, because there are a few milligrams more of it in the tablet, and yet 69% of its magnesium still comes from oxide.

What is allowed on the package?

"For muscles and nerves" or something similar is printed on many magnesium packages. Behind it are claims that have been reviewed and authorized in the EU. For magnesium there are ten, for example that it contributes to normal muscle function, to normal functioning of the nervous system and to the reduction of tiredness and fatigue. The EU list of authorized health claims makes no distinction by form, and the fact that citrate is absorbed better than oxide comes from studies and isn't on any official list.

High-dose magnesium: why isn't 400 mg better?

With magnesium from supplements, more isn't better, because 400 mg is above the limit that applies in the EU. The European Food Safety Authority (EFSA) lists 250 mg per day as the upper limit for magnesium from food supplements, and magnesium from food doesn't count toward it.

The limit comes from the gut. The EU's Scientific Committee on Food reviewed studies for it in which things stayed calm up to this amount, while from around 360 mg some participants developed loose stools. Germany's Federal Institute for Risk Assessment (BfR) applies the same maximum amount.

In our comparison, ten of the 13 supplements deliver 400 mg per day. That's 150 mg more than the upper limit listed by EFSA, and one more sits above it too at 350 mg. In eight of these eleven, the entire daily amount is also packed into a single tablet, capsule or effervescent tablet, so there's no way to take a smaller dose. "High-dose" describes the amount, the word says nothing about quality.

A supplement doesn't need to deliver that much anyway, because the German Nutrition Society (DGE) gives a reference value of 350 mg a day (men) and 300 mg (women), and that's the total from food, drinks and supplement. More on this in our article on magnesium dosage and the upper limit.

Magnesium from drugstores, pharmacies or online: what are the differences?

In our comparison, the difference between drugstores and pharmacies was mainly in the price and hardly in the form. All three drugstore products and three of the five pharmacy products were pure magnesium oxide.

Many people deliberately buy their magnesium at drugstores, others prefer the pharmacy because it somehow feels "safer" there. Going by our numbers, that makes surprisingly little difference to the form. The pharmacy did offer two exceptions, the effervescent tablet with citrate and the licensed medicine, whose product information states every compound down to the milligram.

Online, most forms are listed on the label, but four out of five products still contain oxide. Wherever you buy, you have to check the back of the package.

Best magnesium supplement: what did Stiftung Warentest and Öko-Test test, and what didn't they?

There's no current magnesium test winner from Stiftung Warentest, Germany's leading consumer testing organization. At least, as of September 30, 2026, test.de had no test that compares and rates magnesium supplements. The article "Does magnesium help with muscle cramps?" from February 2026 reviews studies, and the magazine article "Magnesium supplements: a treat for your calves" dates back to October 2001. The prices there are still in pfennigs.

Öko-Test, another German consumer magazine, on the other hand, tested 28 supplements in June 2026, but the results per product are only available behind a paywall. Publicly, the magazine names four points of criticism: for healthy adults, the supplements are generally unnecessary, every second one exceeds the BfR maximum amount, and there are controversial additives such as sweeteners and talc, plus missing information on the package. Christine Throl, a biologist at Öko-Test, puts it like this (our translation): "The magnesium supplements in our test cost up to 1.25 euros a day. Healthy people can usually save their money."

We don't disagree at all. The DGE also considers a real magnesium deficiency "relatively rare", as long as someone eats a balanced diet and has a healthy metabolism. A supplement is there for the gap, after all, and whether you have one, you can estimate pretty well with our overview of foods high in magnesium.

None of the four points of criticism asks about the form, and that's what our comparison is about. By the way, many of the "test winner" lists you find when searching come from comparison portals or from manufacturers themselves, and because we make a magnesium ourselves, we're not crowning a winner here.

Where does CALM stand in this comparison?

CALM is the last row in the table and meets all three criteria we measure the others by: no magnesium oxide, stated shares and an amount below the upper limit. Two capsules a day deliver 206 mg of elemental magnesium from bisglycinate and citrate, mixed in a ratio of 65 to 35, plus 2.0 mg of vitamin B6 in its active form.

I developed CALM together with doctors and nutrition scientists, and every decision in it has a reason. We combined the two forms deliberately, because each is good at something different. Citrate dissolves easily and is quickly available to the body, while bisglycinate follows more slowly and is particularly well tolerated, even if you take it every day. We left out oxide, because the body only absorbs a small part of it and the rest binds water in the gut. At 206 mg, CALM complements your food and therefore stays below the 250 mg. And because it comes as two standard capsules, the dose can be split: both with dinner, or one each with two meals.

CALM costs €27.99 per jar with 30 daily servings, which works out to €0.93 a day and keeps it under €1. That's the highest price in our table, and we stand by it. Because for that, you get two forms we combined on purpose, in an amount below the upper limit, and none of the oxide that's in every one of the supplements up to €0.17 a day.

What does the magnesium that actually gets absorbed cost?

The price per milligram on the label unfortunately says little about how much magnesium you really get into your body for your money. So we worked it out for the pure oxide supplements in our table that have a fixed daily amount of 400 mg. Our calculation is based on the roughly 4% that was absorbed in a comparison of four commercial supplements made from magnesium oxide. The number comes from a single study with US supplements, but it works perfectly well as a rule of thumb. Of 400 mg on the package, only about 16 mg actually reaches you, and measured against the 300 mg the DGE sets for women, that's just around 5%.

So the bargain on the label quickly turns into a supplement that brings you just about 16 mg a day, regardless of whether you pay 5 or 43 cents for it in our table.

Unfortunately, we can't do that kind of calculation for CALM, because there's no measured absorption rate for our blend, and we don't make up numbers. But the direction is documented, and it's pretty clear. In human studies, a lot more magnesium got through from citrate than from oxide. In the double-blind study with 46 adults mentioned above, citrate produced the highest blood levels, while oxide didn't even beat the placebo, and back in a 1990 study from Texas, magnesium in the urine rose many times more after citrate than after oxide. So with CALM, you're not paying for an impressive number on the label of which only a fraction ends up absorbed, but for 206 mg from citrate, which is demonstrably absorbed better than oxide, and bisglycinate, which is considered particularly easy to digest. That's exactly why we think €0.93 a day is really money well spent.

If you also take vitamin D or zinc, our article on combining magnesium explains how they fit together. We made CALM to hold up to a look at the label, and you can measure it by that just like any other supplement.

FAQ

Which magnesium complex is the best?

The best magnesium complex isn't mostly magnesium oxide, discloses the share of each form and delivers no more than 250 mg of magnesium per day. In our comparison, none of the four complexes we checked met all three points, so we're not naming a winner. Our own CALM meets all three, and you can check the criteria on any label yourself.

Is expensive magnesium better than cheap magnesium?

Not automatically, because the most expensive supplement in our comparison was pure magnesium oxide. What justifies a higher price is the form, and there the studies point in a clear direction. In a 60-day study, citrate produced the highest magnesium levels in the blood, while oxide did no better than the placebo. That's exactly what you pay for with CALM: bisglycinate and citrate instead of oxide, 206 mg below the upper limit, at €0.93 a day.

Does a magnesium complex have side effects?

The typical side effect is loose stools, in the worst case diarrhea, with a complex just like with any other magnesium supplement, and the risk rises with the amount. More on this, including medications, in our article on side effects.

When should you take a magnesium complex?

Ideally with a meal, whether it's a complex or a single form, because the body absorbs a bit more magnesium with food than without. Whether morning or evening suits you better is covered in our article on when to take magnesium.

Why is magnesium oxide so cheap?

Magnesium oxide is about 60% magnesium, so it takes very little material to make 400 mg. In our comparison, pure oxide tablets cost from €0.05 a day. Very little of it is absorbed, though. In a comparison on healthy volunteers, it was about 4%.

What is the difference between a magnesium complex and magnesium bisglycinate?

Magnesium bisglycinate is a single magnesium compound, a magnesium complex is a mix of several. In our comparison, bisglycinate appeared on the label of three of the four complexes, each time without stating how much magnesium comes from it.

Disclaimer:

This article is for informational purposes only and does not replace medical advice, diagnosis, or treatment by a physician or pharmacist. The information provided here should not be used for self-diagnosis or self-treatment. Food supplements are no substitute for a balanced, varied diet and a healthy lifestyle. For any health questions or complaints, please always consult a doctor you trust. Fifty Five accepts no liability for any inconvenience or harm resulting from the use of the information presented here.

Sources

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