Magnesium - Dietary Supplements

How to Choose the Right Magnesium

Choosing the right magnesium isn’t just a matter of comparing prices: not all forms (salts) are absorbed by the body in the same way. Magnesium bisglycinate, magnesium citrate, malate, glycerophosphate, L-threonate, or oxide—each form has different bioavailability and uses, which raises the recurring question: which form of magnesium should you choose?

According to a well-known study (“Global estimation of dietary micronutrient inadequacies: a modeling analysis”), approximately 2.4 billion people worldwide—nearly one-third of the global population (31%)—have a dietary magnesium intake below recommended levels, particularly during periods of stress or fatigue, two signs often associated with magnesium deficiency, just as poor-quality sleep is.

Our products are developed and selected with cutting-edge expertise to offer highly bioavailable magnesium, free of unnecessary additives, and with the best value for money. Let’s take a closer look at our complete range of magnesium products.

The %NRV doesn’t tell the whole story: what matters is the magnesium that’s actually absorbed

The %NRV (Nutrition Reference Values) listed on a product’s label only indicates the amount of elemental magnesium contained in the dose, not the amount your body actually absorbs.

Two supplements with very different %NRVs can therefore, once digested, provide comparable—or even opposite—amounts of magnesium. That’s why a high %NRV is never, on its own, a guarantee of effectiveness.

A magnesium oxide supplement labeled at 150% of the NRV provides approximately 560 mg of elemental magnesium, but with a bioavailability of about 4%, a large portion is not absorbed. Furthermore, magnesium oxide can cause gastrointestinal upset in most people.

A bisglycinate-based supplement containing only 30% of the NRV provides less on paper, but its absorption mechanism—which is independent of stomach acidity—allows for a significantly higher proportion to be absorbed and offers much better digestive tolerance.

At an equivalent actual dosage, its absorption efficiency is therefore much higher. The %NRV alone is therefore not sufficient to compare two different forms with each other.

The %NRV remains a valid benchmark for comparing two products based on the same magnesium salt. However, it loses all relevance when comparing two different forms; this is where bioavailability takes over as the deciding factor, even before considering the price listed on the bottle.

Bisglycinate, citrate, malate, glycerophosphate, L-threonate, oxide: which form of magnesium is actually absorbed by the body?

Magnesium comes in a dozen different salts, divided into three families—inorganic, organic, and chelated—which differ in both bioavailability and digestive tolerance. Here are the main ones, along with their efficacy profiles.

• Bisglycinate: a chelated salt that is well absorbed via amino acid transporters in the intestinal wall, rather than solely through conventional ion channels. Good digestive tolerance, with very little laxative effect.
• Citrate: Adequate bioavailability, with results varying across studies (from ~30% to over 50%, depending on the measurement method). Good balance between bioavailability and cost; widely used.
• Malate: an organic salt associated with cellular energy metabolism (the Krebs cycle). Human bioavailability data remain limited compared to citrate or bisglycinate.
• Glycerophosphate: an organic salt, generally well tolerated. A comparative study of 15 commercial formulations ranked it among the best absorbed, alongside citrate and bisglycinate.
• L-threonate: a newer salt, studied for its ability to cross certain cell membranes. Comparative data remain limited compared to older, better-documented forms.
• Oxide: low bioavailability, estimated at about 4% (Firoz & Graber, 2001). An inexpensive mineral salt but poorly absorbed, with a marked laxative effect at high doses.

A comparative study published in 2025 in the journal *Nutrients* tested the bioavailability of seven magnesium salts commonly used in food products, including bisglycinate, oxide, citrate, and chloride. The study was conducted to objectively confirm what many magnesium users have observed: absorption—and therefore actual effectiveness—varies significantly depending on the chemical base used. Magnesium bisglycinate, thanks to its chelated form, is better tolerated by the digestive system than mineral salts such as magnesium oxide.

What Magnesium Actually Does in Your Body

Magnesium is involved in more than 300 enzymatic reactions. Several health claims have been validated by the EFSA under EU Regulation 432/2012, as well as by the FOPH/FSVO under the FDHA Ordinance on Food Information (OIDAl), Annex 14:

• Magnesium helps reduce fatigue.
• Magnesium contributes to electrolyte balance.
• Magnesium contributes to normal energy metabolism.
• Magnesium contributes to the normal functioning of the nervous system.
• Magnesium contributes to normal muscle function.
• Magnesium contributes to normal protein synthesis.
• Magnesium contributes to normal psychological function.
• Magnesium contributes to the maintenance of normal bones.
• Magnesium contributes to the maintenance of normal teeth.
• Magnesium plays a role in the process of cell division.
• When combined with vitamin B6, magnesium also helps regulate hormonal activity—a common combination of magnesium and vitamin B6 in our products, as vitamin B6 promotes the body’s absorption of magnesium.

This magnesium + vitamin B6 synergy is one of the most sought-after during times of stress.

People experiencing stress can find that magnesium supports their nervous system; athletes can find support for muscle function and relief from cramps; and those with restless nights can use it as a supplement to complement healthy sleep habits—though magnesium should not replace medical care for persistent sleep disorders.

Cramps, fatigue, irritability, poor sleep: signs of insufficient magnesium intake

An insufficient magnesium intake can manifest in several ways: muscle cramps, persistent fatigue, irritability, and sleep disturbances. These symptoms, whether occurring individually or in combination, often prompt people to consider supplementation.

According to ANSES, dietary magnesium intake often falls short of recommendations, particularly during periods of prolonged stress or intense physical activity.

These symptoms do not constitute a diagnosis of magnesium deficiency: a blood test performed by a healthcare professional remains the only reliable way to confirm a deficiency.

Our magnesium dietary supplements can help address an insufficient intake, in addition to a varied and balanced diet, and not as a substitute for it.

Marine Magnesium: A Unique Source

Marine magnesium, extracted from seawater, is actually composed largely of magnesium chloride and magnesium oxide salts. Its absorption rate is similar to that of magnesium oxide—and therefore rather low—despite the “natural” image often highlighted on packaging and sometimes justified by a high price. Chelated salts such as bisglycinate or glycerophosphate offer better absorption than raw marine salts.

Bisglycinate, citrate, malate, glycerophosphate: the right choice for your needs

The choice depends mainly on your goal; here is a list of guidelines by profile to consider before adding a product to your cart:

• Stress Profile: Bisglycinate and glycerophosphate, which are well-tolerated and associated with normal nervous and psychological system function, are often recommended first for their effectiveness and good digestive tolerance. These are also the forms preferred by those whose stress affects their sleep.
• Sports Profile: Malate, which is linked to cellular energy metabolism, is well-suited for exercise-related fatigue. Some sports formulas also combine magnesium with taurine, an amino acid sometimes cited for its role in muscle recovery; however, the effectiveness of this magnesium-taurine combination remains to be validated depending on the specific formula chosen. Taurine is often added to these formulas to complement magnesium’s effect on recovery.
• For those with sensitive digestion: bisglycinate or malate are better tolerated than oxide, which is very often reported to have a laxative effect at high doses. The bioavailability of these magnesium supplements also makes them a suitable choice for optimal results at lower doses.

It should be noted that, in many cases, improved sleep and recovery are beneficial and necessary for a number of physiological conditions.

Capsules, tablets, magnesium powder: the different dosage forms

Beyond the chemical composition, the dosage form is also an important consideration when purchasing. Capsules remain the most common format and the easiest to dose on a daily basis. Tablets sometimes allow for higher dosages per serving but may contain more excipients and manufacturing aids; compared to capsules, these tablets are also sometimes harder to split.

Powder is suitable for people who have difficulty swallowing capsules or tablets, as the dose can be easily divided. You can also open your capsules and dissolve the contents in a glass of water. Be aware, however, that the taste can sometimes be unpleasant. For vegan diets, also make sure the capsules are plant-based and not animal-derived.

The price of a high-quality magnesium supplement

The price of a magnesium supplement varies widely depending on the form, the actual dosage of elemental magnesium, and the brand. A low-cost product containing mainly magnesium oxide will actually end up being more expensive to use than a higher-priced product that is better absorbed: you’ll need a larger dose to achieve a comparable effect, which drives up the actual cost per treatment course, in addition to its potential adverse effects on digestion.

In other words, the lowest price on the shelf is almost never the lowest price in terms of effectiveness. Comparing the price to the actual dosage of elemental magnesium per capsule—rather than the listed price of the bottle—is still the best approach to evaluating a product’s value for money, regardless of your budget or how much you’re willing to spend.

What to Keep in Mind Before Adding a Magnesium Supplement to Your Cart

For optimal bioavailability, bisglycinate, glycerophosphate, and malate remain the top choices to add to your cart. Citrate also offers a good balance of price and effectiveness. Malate and glycerophosphate are suitable for fatigue related to physical activity. Magnesium oxide and marine magnesium, while inexpensive, are the least well-absorbed forms and should only be added to your cart with full awareness of their limitations. In short, it’s better to choose a slightly more expensive product that’s actually absorbed than a bargain-priced option that isn’t effective.

View all our magnesium supplements or contact us for more information on this topic. Magnesium is also part of our Minerals selection: other products to complement your supplement regimen based on your needs, at the best prices.

Magnesium and Sports: An Ally for Recovery?

Active individuals lose more magnesium through sweat, which can exacerbate an already insufficient intake among certain athletes, leading to fatigue and less restorative sleep.

Magnesium contributes to normal muscle function and the reduction of fatigue—two EU-approved health claims that are beneficial for supporting a regular training regimen. Malate, which is involved in cellular energy metabolism, is often preferred by athletes as a supplement to a balanced diet and proper hydration; it is sometimes combined with taurine in formulas designed for recovery. Glycerophosphate is also a viable option. Check out our other minerals to round out your fitness routine.

What are the benefits of taking magnesium?

The recommended intakes for magnesium are based on the assumption of a varied diet that is sufficiently rich in this mineral. However, several factors specific to our modern lifestyle make this balance harder to achieve than it was a few decades ago. Intensive farming and soil depletion reduce the mineral content of many fruits and vegetables: a landmark study of 43 American vegetable crops revealed significant declines in several nutrients between 1950 and 1999 (Davis, Epp & Riordan, 2004).

Added to this are a more stressful lifestyle—which increases the body’s physiological need for magnesium and impacts sleep quality—a growing consumption of processed foods that are lower in micronutrients, and environmental exposure (pollution, tobacco, alcohol) that can affect its absorption or excretion.

The global result: approximately 2.4 billion people—nearly one-third of the population—currently have a dietary magnesium intake below the recommended levels (Passarelli et al., 2024, The Lancet Global Health). In this context, targeted supplementation may be a sensible way to bridge this gap, as a complement to (and not a replacement for) a varied and balanced diet.

Your Questions About Magnesium and Its Forms

What is the difference between magnesium bisglycinate and magnesium oxide?

Bisglycinate is a chelated salt bound to two glycine molecules, offering high bioavailability and good digestive tolerance. Magnesium oxide, a more common mineral salt, has much lower bioavailability, around 4%. As mentioned above, a comparative study on PubMed confirms this difference in effectiveness between the two forms.

When should you take magnesium: in the morning or at night?

When taken in the evening with a meal, magnesium can promote muscle relaxation at the end of the day and support better sleep. Splitting the dose is an option to improve digestive tolerance. Bisglycinate can be taken at any time of day, while malate is sometimes preferred in the morning under certain conditions. Follow the dosage instructions on the product label or contact us for more information.

How long does a magnesium treatment course last?

A standard course of treatment generally lasts 1 to 3 months, either continuously or with a 2- to 4-week break before resuming. If a blood test confirms insufficient magnesium intake, it is recommended to consult a doctor or healthcare professional to adjust the duration. The dietary supplement does not replace a daily diet rich in magnesium, but rather complements it.

Magnesium and Kidney Failure: What Precautions Should Be Taken?

Magnesium is not recommended in cases of severe kidney failure, due to the risk of accumulation that the kidneys can no longer regulate. At doses recommended and approved by health organizations, a normal dietary intake remains safe for a healthy adult. If you have a kidney condition, consult a doctor before taking a supplement.

Can magnesium be taken during pregnancy?

Magnesium is an essential mineral during pregnancy. The most appropriate dose and form should be determined by a healthcare professional, taking into account the intake already provided by the diet. It is recommended not to exceed the recommended daily intake without medical supervision.

Is marine magnesium as effective as bisglycinate?

No, not in terms of the actual amount of magnesium delivered to the body: marine magnesium consists largely of oxide and chloride salts, which are less readily absorbed than chelated salts such as bisglycinate. Its advantage lies in its natural origin, but for better absorption and greater effectiveness, bisglycinate or citrate are generally preferred.

What is the recommended daily intake of magnesium?

Recommended daily intakes vary depending on age, gender, and circumstances (pregnancy, intense physical activity). They generally range from 300 to 400 mg per day for an adult. A pharmacist can tailor this dosage to your specific needs.

Can magnesium cause digestive problems?

Yes, certain salts—particularly oxide—can have a laxative effect at high doses due to their low intestinal absorption. Chelated forms such as bisglycinate are better tolerated by the digestive system. Dividing the dose into several smaller doses throughout the day can also help limit this discomfort.

Magnesium citrate or magnesium bisglycinate: which should you choose first?

Magnesium citrate offers a good balance between bioavailability and price, making it an attractive entry-level option. Magnesium bisglycinate goes a step further in terms of bioavailability, effectiveness, and digestive tolerance, though it generally comes at a slightly higher price. For a first purchase without budget constraints, bisglycinate remains the safest choice.

Glycerophosphate and L-threonate: two lesser-known forms—what are they used for?

Magnesium glycerophosphate is an organic base that is easily absorbed, often combined with malate in sports formulas, and well tolerated by the digestive system. L-threonate is a newer base that is more expensive to manufacture; it has been studied for its ability to cross certain cell membranes, such as the blood-brain barrier. However, the available data on its bioavailability remains limited compared to bisglycinate or glycerophosphate.

Text validated by our panel of experts

This content was written by our panel of experts in accordance with European regulations on health claims (EU Regulation No. 432/2012). No misleading therapeutic claims are made on this page.

Text validated by Aebi Keven, founder of ProFeel Life sàrl and Nutricraft SA, a producer and distributor of nutraceutical solutions.

Dietary supplements are not a substitute for medical treatment or a varied and balanced diet. Keep out of reach of children.