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Using the best form of magnesium: oxide vs citrate

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What forms of magnesium are there?

In supplements, magnesium generally comes in the following forms:

  • Magnesium chloride
  • Magnesium sulphate
  • Magnesium citrate
  • Magnesium oxide
  • Magnesium bisglycinate
  • Magnesium orotate
  • Magnesium L-threonate

The difference?

There are many different forms of dietary magnesium. In supplements, magnesium chloride is one of the most popular options, and magnesium sulphate, also known as Epsom salt, is usually restricted to use as a laxative and as a topical substance.

Magnesium oxide is generally considered to be one of the safer and more effective forms of dietary magnesium, but it has its downsides. For instance, if your lungs are exposed to magnesium oxide powder, it potentially could be fatal, which doesn’t speak well to this substance’s safety as a supplement.

Magnesium citrate, on the other hand, belongs to a new class of supplements that use either citric acid or glycine as bases for essential minerals. This new class of supplement-delivery technologies is much more effective, and it offers greater bioavailability and fewer side effects.

Magnesium bisglycinate is another highly bioavailable form of this essential mineral, and magnesium orotate has been developed specifically to help heal tissue and improve artery health, Magnesium L-threonate is a niche form of this mineral that is mainly used to help with memory issues. Ultimately, magnesium chloride, oxide, and citrate are the most commonly used in supplements.


  • Magnesium chloride is the old standby when it comes to magnesium supplements, but it might have bioavailability issues
  • Magnesium sulphate and oxide aren’t highly suitable for use in supplements, but magnesium oxide remains a relatively popular supplement ingredient
  • Magnesium citrate and bisglycinate are examples of new forms of magnesium that are safer and more bioavailable.
  • Magnesium orotate and L-threonate have been altered to have special benefits for certain specific applications

Why is magnesium in citrate form better?

Studies show that magnesium citrate is much more bioavailable than magnesium oxide. One study found that magnesium oxide had no solubility in water, and it had a peak solubility of 43% in stomach acid. Magnesium citrate, on the other hand, was 55% soluble in water alone, and it was bioavailable in rates far exceeding that level in stomach acid.

Since magnesium citrate is relatively new on the market, these results haven’t yet been replicated, and there isn’t a lot of research on the improved bioavailability of this form of magnesium supplement. All the available research and theory, however, points to the conclusion that combining magnesium with citric acid is one of the most bioavailable ways to prepare this essential mineral.


  • Among the various forms of magnesium supplements, magnesium oxide has one of the lowest bioavailability scores, and magnesium citrate has one of the highest
  • Magnesium citrate is one of the newest forms of magnesium on the market, and it’s part of the next generation of highly bioavailable supplements

Why do we use magnesium citrate instead of other forms?

The world of supplements is very different than it used to be. Much of what we currently know about how to make and use supplements is over a century old, but innovators in pharmacology continue to create better forms of vitamins and minerals that are healthier for your body.

Magnesium citrate is an example of a supplement form that completely redefines a particular nutrient. Traditionally, magnesium has been one of the hardest essential minerals to take due to its low inherent bioavailability, and this mineral was uncharacteristically hard to bind to carriers.

With the advent of magnesium citrate, however, getting your RDV of magnesium became safe and simple. We’re proud to honour this momentous development in the history of supplement science by ditching magnesium oxide and going with next-generation magnesium citrate in Feel Multivitamin™.

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About the author
Katie Hipwell - Katie is an AfN Registered Nutritionist (RNutr) with a specialism in food and is Head of Nutrition at Feel. Katie has worked in the food supplement industry for 10 years. She has completed a Master's degree in Human Nutrition and an undergraduate degree in BSc Sport and Exercise Nutrition.
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