Magnesium is an essential mineral involved in hundreds of processes throughout the body. But magnesium supplements aren't all the same. Different forms of magnesium contain different compounds, which can affect how they behave in the body and how much magnesium is available for absorption.
Magnesium glycinate, magnesium citrate, magnesium oxide and other forms are therefore not simply interchangeable names for the same ingredient.
So what actually makes them different?
First: What Does “Magnesium” on a Supplement Label Mean?
One of the most important things to understand is the difference between the magnesium compound and elemental magnesium.
For example, magnesium glycinate is a compound made by combining magnesium with glycine, an amino acid. The weight of the complete magnesium glycinate compound is therefore greater than the amount of elemental magnesium it provides.
When a supplement states its elemental magnesium amount, it is referring to the actual amount of magnesium supplied, rather than the total weight of the magnesium-containing compound.
This distinction is important when comparing products.
A product containing a larger number of milligrams of a magnesium compound does not necessarily provide more elemental magnesium.
The National Institutes of Health Office of Dietary Supplements specifically explains that supplement labels declare the amount of elemental magnesium rather than the total weight of the magnesium-containing compound.
What Is Magnesium Glycinate?
Magnesium glycinate is a form of magnesium in which magnesium is bound to glycine, an amino acid.
It is often described as a magnesium amino-acid chelate or magnesium bisglycinate.
The form of magnesium matters because different magnesium compounds have different chemical properties, including differences in solubility and absorption.
Magnesium glycinate is commonly used in dietary supplements and is one of several forms available alongside magnesium citrate, magnesium oxide, magnesium chloride and others.
Rather than asking which form is universally “best”, it is more useful to look at what form a product contains, how much elemental magnesium it provides, and what the overall formula is designed to provide.
Research has compared amino-acid chelated magnesium with other forms. In one randomized, double-blind study involving 46 healthy adults, an amino-acid chelate and magnesium citrate showed greater absorption than magnesium oxide after longer-term supplementation. However, the study did not establish that amino-acid chelated magnesium is universally superior to every other magnesium preparation.
Magnesium Glycinate vs Magnesium Citrate
Magnesium citrate combines magnesium with citric acid.
It is one of the more commonly used forms of magnesium supplementation and has been studied for its absorption characteristics.
Research comparing magnesium citrate with magnesium oxide has found differences in solubility and bioavailability.
For example, a clinical study found that magnesium citrate was substantially more soluble than magnesium oxide and produced greater magnesium absorption in the participants studied.
A separate randomized study also found greater bioavailability from magnesium citrate than magnesium oxide.
That does not mean magnesium citrate is automatically the right choice for everyone.
The form used in a supplement depends on the overall formulation, the amount of elemental magnesium provided, the intended use and individual tolerance.
Magnesium Glycinate vs Magnesium Oxide
Magnesium oxide is another widely available form of magnesium.
It contains a relatively high proportion of elemental magnesium by weight, but it is less soluble than some other magnesium compounds.
Research comparing magnesium citrate and magnesium oxide has found differences in solubility and measures of absorption.
In one study, magnesium oxide was substantially less soluble than magnesium citrate and produced lower urinary magnesium increases following supplementation.
Another randomized controlled study similarly found higher bioavailability for magnesium citrate than magnesium oxide.
However, research on magnesium absorption is not completely uniform. Different studies use different doses, populations, formulations and methods for measuring magnesium status and absorption.
This is why simply comparing the number of milligrams printed on the front of two products can be misleading.
The form of magnesium and the amount of elemental magnesium both matter.
What About Magnesium Threonate?
Magnesium threonate is another form that appears in the supplement market.
It is chemically different from magnesium glycinate, citrate and oxide and has attracted research interest, including research investigating its potential effects on cognitive and sleep-related outcomes.
However, findings from research on one magnesium form should not automatically be applied to other forms of magnesium.
When comparing magnesium supplements, it is important to look at research on the specific form being discussed rather than assuming that all magnesium compounds behave identically.
Does a Higher Number of Milligrams Mean a Better Magnesium Supplement?
Not necessarily.
This is one of the easiest mistakes to make when comparing magnesium products.
Consider two hypothetical products:
Product A
1,000 mg magnesium compound
providing 100 mg elemental magnesium
Product B
500 mg magnesium compound
providing 150 mg elemental magnesium
Product A contains more of the magnesium compound by weight, but Product B provides more actual elemental magnesium.
This is why elemental magnesium is the more useful number when comparing the magnesium contribution of different products.
The NIH Office of Dietary Supplements confirms that the amount declared on supplement labels refers to elemental magnesium rather than the entire weight of the magnesium compound.
Why the Form Matters
Different magnesium compounds have different chemical characteristics.
Their solubility can vary, and research indicates that magnesium absorption can differ depending on the form.
The NIH notes that magnesium forms that dissolve more readily in liquid generally tend to have greater absorption, and identifies citrate, chloride, lactate and aspartate as forms that have shown greater bioavailability than magnesium oxide and magnesium sulfate in some studies.
Research comparing magnesium citrate and magnesium oxide provides an example of this difference. Magnesium citrate was substantially more soluble and showed greater bioavailability than magnesium oxide in one clinical study.
This does not mean there is one universally superior form of magnesium.
Different forms have different characteristics, and the appropriate choice depends on factors such as:
- The form of magnesium
- The amount of elemental magnesium
- The serving size
- The overall formulation
- The intended use
- Individual tolerance
- The other ingredients in the product
The evidence is therefore better understood as showing that different magnesium forms can behave differently, rather than proving that one form is always the best choice.
What Should You Look for When Choosing a Magnesium Supplement?
Rather than choosing a product based only on the largest number on the front of the bottle, look at the ingredient information.
1. Look for the Actual Magnesium Amount
Check how much elemental magnesium is provided per recommended serving.
This gives you a more useful basis for comparison than the total weight of the magnesium compound.
2. Check Which Form of Magnesium Is Used
Look for the specific compound, such as:
- Magnesium glycinate
- Magnesium citrate
- Magnesium oxide
- Magnesium chloride
- Magnesium lactate
- Magnesium threonate
Different forms have different properties, so the form should be clearly stated.
3. Look at the Complete Formula
Magnesium is often combined with other ingredients.
If you're comparing two products, look beyond the magnesium itself and consider the complete ingredient list and the amount supplied per serving.
4. Consider the Serving Size
Two capsules, four capsules and one scoop may all provide different amounts of elemental magnesium.
Always compare products on a per-serving basis.
Magnesium Glycinate in Maison Véda Night Formula
Maison Véda's Night Formula uses magnesium glycinate as part of a four-ingredient formula.
Each two-capsule serving provides:
Magnesium glycinate — 1,064 mg
Providing 300 mg elemental magnesium
The formula also contains:
- L-Theanine — 200 mg
- Passionflower — 150 mg
- Chamomile — 100 mg
The formula is melatonin-free.
The formula clearly separates the weight of the magnesium glycinate compound from the elemental magnesium it provides, making the magnesium content easier to understand when comparing products.
The Takeaway
There isn't one magnesium form that is universally right for everyone.
Magnesium glycinate, citrate, oxide, threonate and other forms have different chemical properties and can differ in solubility and absorption.
When comparing magnesium supplements, look beyond the largest number on the label.
Check:
The form of magnesium.
The amount of elemental magnesium.
The serving size.
The complete ingredient list.
And the purpose of the overall formula.
Understanding these differences makes it easier to compare magnesium supplements based on what they actually contain, rather than simply comparing numbers on the front of a bottle.
A Note on Magnesium Supplements
Magnesium from supplements contributes to total magnesium intake, and higher supplemental amounts may cause gastrointestinal effects such as diarrhoea in some people.
Magnesium can also interact with certain medicines, and people with impaired kidney function may require particular caution because the kidneys play an important role in maintaining magnesium balance.
If you have a medical condition, take medicines, are pregnant or breastfeeding, or are unsure about magnesium supplementation, speak with an appropriately qualified health professional before use.
Comparing sleep supplements? Learn more about common ingredients, formulations and what to consider when choosing a sleep supplement in Australia in our Sleep Supplements Australia guide →
Sources & Further Reading
National Institutes of Health — Office of Dietary Supplements: Magnesium Fact Sheet for Health Professionals
Comprehensive information on magnesium's functions, dietary sources, supplement forms, elemental magnesium and differences in absorption between magnesium compounds.
NIH — Magnesium Fact Sheet for Health Professionals
Lindberg et al. — Magnesium Bioavailability from Magnesium Citrate and Magnesium Oxide
A clinical study comparing the solubility and gastrointestinal absorption of magnesium citrate and magnesium oxide. The study found magnesium citrate to be more soluble and bioavailable than magnesium oxide.
PubMed — Magnesium citrate vs magnesium oxide
Walker et al. — Magnesium Citrate Found More Bioavailable Than Other Magnesium Preparations
A randomized, double-blind study comparing magnesium citrate, magnesium oxide and an amino-acid chelate in 46 healthy adults receiving 300 mg of elemental magnesium per day.
PubMed — Magnesium preparations and bioavailability
Werner et al. — Assessment of Magnesium Bioavailability from Magnesium Citrate and Magnesium Oxide
A randomized controlled study comparing magnesium citrate and magnesium oxide using measures of urinary magnesium excretion and plasma magnesium concentrations.
PubMed — Magnesium citrate vs magnesium oxide bioavailability
Magnesium Diglycinate vs Magnesium Oxide — Clinical Trial
A randomized crossover study examining magnesium diglycinate and magnesium oxide in people with impaired intestinal absorption.
PubMed — Magnesium diglycinate vs magnesium oxide
Therapeutic Goods Administration — Supporting Claims and Indications for Listed Medicines
Australian guidance regarding evidence and support for claims and indications made for listed medicines.
TGA — Supporting claims and indications for listed medicines
