Recent research consistently shows that most people do not get enough magnesium from their diet alone. Modern lifestyles and high coffee consumption only make matters worse, as both factors accelerate the excretion of magnesium from the body. Yet a magnesium deficiency is about much more than painful muscle cramps — though those can certainly be debilitating. Insufficient magnesium has been linked to asthma, cardiovascular disease, diabetes, migraines, and even depression. This makes it essential not only to supplement magnesium but, crucially, to choose the right form.
What to Look for When Choosing a Magnesium Supplement
Not all magnesium supplements are created equal. At first glance, the element might appear to be the same in every product, but the amount of magnesium per tablet is not a reliable indicator of how much your body will actually absorb. Reaching for products that boast 100%, 200%, or even 300% of the daily reference intake may seem like a good idea — but in reality, it is the form of magnesium that determines its bioavailability and ultimately how much of the mineral is utilised by the body.
So what should you pay attention to? First, look at the percentage of elemental magnesium ions per serving. Research suggests that the best absorption occurs when approximately 120 mg of magnesium ions are delivered in a single dose — which also explains why taking very high doses at once is not necessarily more effective. Secondly, consider supplements that include vitamin D3 (which improves magnesium absorption and bioavailability) and vitamin B6 (which reduces the excretion of magnesium through urine). However, the single most important factor when choosing a magnesium supplement is the type of salt — in other words, the specific form of magnesium it contains.
[tip:Optimal magnesium absorption occurs at around 120 mg of elemental magnesium per dose. Rather than taking one large dose, consider splitting your daily intake across two or three smaller doses for better results.]
The Best-Absorbed Forms of Magnesium
Magnesium Citrate
Magnesium citrate is the clear leader when it comes to bioavailability. Its absorption rate ranges from approximately 25% to as high as 90%, making it the best-absorbed form of magnesium available on the market. This impressive bioavailability results from the combination of citric acid with three molecules of magnesium, creating a highly efficient and cost-effective supplement. It is the most commonly used form for general magnesium supplementation.
One important consideration: citric acid has a mild laxative effect. This makes magnesium citrate an excellent choice for individuals who experience constipation or sluggish bowel movements, but it may not be ideal for those who tend to have loose stools.
Magnesium Lactate
Magnesium lactate is another highly bioavailable form, with absorption rates only slightly lower than citrate. As an organic salt, it naturally exhibits high bioavailability, and approximately 12% of its mass consists of elemental magnesium — making it efficient in delivering the mineral. A significant advantage of magnesium lactate is its gentler effect on the digestive system, with far fewer gastrointestinal side effects than many other forms. This makes it a particularly good choice for children and for anyone with a sensitive stomach.
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Well-Absorbed Forms of Magnesium
Magnesium Chloride
Magnesium chloride is unusual in that, despite being an inorganic compound, it demonstrates absorption levels comparable to organic magnesium salts — making it the best-absorbed inorganic form of magnesium available. Although it contains only about 12% elemental magnesium, its rapid absorption rate places it high on the list of effective supplemental forms. Magnesium chloride also supports kidney function and may help accelerate a sluggish metabolism. However, individuals prone to acid reflux should exercise caution, as magnesium chloride may exacerbate reflux symptoms.
Magnesium L-Threonate
Magnesium L-threonate is a relatively new and increasingly popular form. It is a chelated magnesium compound bound to two molecules of threonate — a metabolite of vitamin C. Research to date suggests good bioavailability and minimal gastrointestinal side effects. However, what truly sets this form apart is its unique ability to cross the blood-brain barrier, potentially increasing magnesium concentration directly in the brain. This makes magnesium threonate an excellent option for supporting the nervous system, cognitive function, and managing stress and anxiety.
Magnesium Malate
Magnesium malate combines magnesium with malic acid — a compound naturally produced during metabolic processes. Its bioavailability reaches approximately 30%. Malic acid is involved in the body's energy production cycle, which gives magnesium malate a particular advantage for individuals dealing with fatigue and low energy levels. It is a popular choice among active people seeking both magnesium replenishment and a natural energy boost.
Magnesium Chelate (Glycinate / Bisglycinate)
Magnesium glycinate — also known as magnesium bisglycinate or chelated magnesium — is formed by binding two molecules of the amino acid glycine to magnesium through a chelate bond. This specific structure protects the magnesium from premature degradation in the stomach, resulting in less loss during digestion and better absorption in the small intestine. Bioavailability reaches approximately 24%.
Beyond its absorption profile, magnesium glycinate is particularly valued for its gentle effect on the body. The likelihood of diarrhoea is very low, and glycine itself has a calming effect that may support relaxation and sleep quality. This makes it an excellent choice for long-term supplementation aimed at correcting magnesium deficiency, and it is widely considered one of the safest forms for use during pregnancy.
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Niche and Specialised Forms
Magnesium Sulphate (Epsom Salt)
Magnesium sulphate — commonly known as Epsom salt — is primarily used in pharmaceutical and clinical settings. Its oral bioavailability is low, reaching only about 7%, and it can easily cause diarrhoea at higher doses. For this reason, magnesium sulphate is best suited for external use — such as bath soaks — rather than daily oral supplementation.
Magnesium Taurate
Magnesium taurate is a less common but interesting form that combines magnesium with the amino acid taurine. It is particularly well suited for individuals with cardiovascular concerns, including a tendency toward heart arrhythmia. Taurine itself offers protective benefits for blood vessels. The compound is well absorbed, though its elemental magnesium content is relatively modest at around 9%.
The Least Effective Forms of Magnesium
Magnesium Carbonate
Magnesium carbonate forms an inorganic bond with carbonic acid and, once in the stomach, converts to magnesium chloride upon contact with hydrochloric acid. Its bioavailability in studies has been generally lower than that of magnesium oxide. However, it does have one notable advantage: it may be a reasonable option for individuals suffering from acid reflux or indigestion, as it has a mild antacid effect, and side effects are rare.
Magnesium Oxide
Magnesium oxide — a simple bond between magnesium and oxygen — is the cheapest and most widely available form of magnesium. It is also, unfortunately, the least effective, with a bioavailability of only about 4%. Some studies have found no significant difference between magnesium oxide supplementation and placebo, suggesting minimal real-world benefit. Despite its prevalence on shop shelves, magnesium oxide is generally the poorest choice for those looking to meaningfully increase their magnesium levels.
[note:When comparing magnesium supplements, always check the form — not just the total milligrams per tablet. A 500 mg magnesium oxide tablet may deliver far less absorbable magnesium than a 200 mg magnesium citrate capsule.]
Which Magnesium Is Best for Muscle Cramps?
Muscle cramps are one of the most common and recognisable symptoms of magnesium deficiency. When supplementation is introduced, cramps typically improve relatively quickly regardless of the specific form — provided it has adequate bioavailability. For the fastest and most reliable results, choose a highly bioavailable form such as magnesium citrate, glycinate, or malate, ideally with added vitamin D3 and B6 to maximise absorption and minimise excretion.
Explore our complete magnesium supplement collection to find the right form, dosage, and combination for your individual needs — from citrate and glycinate to threonate and taurate, all from trusted international brands and shipped across Europe.
[warning:This article is for informational purposes only and does not replace medical advice. If you suspect a serious magnesium deficiency or experience symptoms such as persistent muscle cramps, irregular heartbeat, or chronic fatigue, consult a healthcare professional for proper assessment and guidance.]
Key Takeaway: The form of magnesium matters far more than the milligrams on the label. Magnesium citrate offers the highest overall bioavailability, while glycinate is the gentlest for long-term use and pregnancy, threonate stands out for brain and nervous system support, malate is ideal for combating fatigue, and taurate best serves cardiovascular needs. Avoid magnesium oxide for supplementation purposes — its extremely low absorption makes it a poor investment. Whichever form you choose, pairing magnesium with vitamins D3 and B6 can further enhance its effectiveness.
