When I first started buying magnesium supplements, I realised how confusing the labels could be. One number appeared on the front, another on the back, and most times you needed several capsules to get the advertised amount.
That is when I learned how important elemental magnesium is. So what does it actually mean, how do you find it on the label and why does it matter?
What does elemental magnesium actually mean?
Magnesium in a supplement does not usually come on its own. It is joined to another substance, such as glycine in magnesium glycinate or citric acid in magnesium citrate.
This means the total weight of the magnesium compound is not the same as the amount of actual magnesium it contains. The actual magnesium inside the compound is known as elemental magnesium.
A simple example using magnesium glycinate
Around 700 mg of magnesium glycinate may provide approximately 100 mg of elemental magnesium. The rest of the compound is the glycinate part attached to it.
So, magnesium glycinate tells you which form you are taking, while 100 mg tells you how much actual magnesium it provides.
Does elemental magnesium have its own benefits?
No, it does not have any special benefits. It has the same benefits magnesium is known for, including supporting healthy bones, energy production and the normal functioning of your muscles and nerves.
If you are deficient, getting enough magnesium may also help improve symptoms such as tiredness, weakness and muscle cramps.
But remember, the effect of a supplement still depends on the dose, the form, how well you absorb it and whether you need extra magnesium.
How to find elemental magnesium on the label
Unfortunately, magnesium labels are not all written in the same way. Some clearly say “elemental magnesium”, while others simply say “magnesium”. The form may be shown next to it, elsewhere on the label or in the ingredients list.
For example, you might see:
Magnesium: 100 mg
From magnesium glycinate
Or:
Magnesium: 100 mg
As magnesium glycinate
In both cases, 100 mg is the elemental magnesium amount. On a Supplement Facts panel, the magnesium number refers to elemental magnesium rather than the weight of the whole magnesium compound.
Always check the serving size too. That 100 mg might come from one capsule, but it could also be the amount provided by two, three or even four capsules.
I would be cautious if you cannot find the form of magnesium anywhere on the packaging or product page. A label that simply says “magnesium” does not give you enough information to properly compare the supplement.
How much elemental magnesium is in different forms?
Different forms of magnesium contain different percentages of elemental magnesium because the substances attached to magnesium have different weights.
For example, oxygen is very light, so magnesium makes up a large part of magnesium oxide. Glycine, citrate and malate are heavier, so magnesium makes up a smaller part of those compounds.
This becomes easier to understand when you compare the same amount of each form. In 100 mg of magnesium oxide, around 60 mg is elemental magnesium. In 100 mg of magnesium glycinate, only around 14 mg is elemental magnesium.
Elemental magnesium by form
| Magnesium form | Approximate elemental magnesium by weight | What this means |
|---|---|---|
| Magnesium glycinate | Around 12% to 14% | Around 12 to 14 mg in every 100 mg of the compound |
| Magnesium citrate | Around 12% to 16% | The percentage depends on the particular version of magnesium citrate |
| Magnesium oxide | Around 60% | Around 60 mg in every 100 mg of the compound |
| Magnesium malate | Around 15% (some dimagnesium malate ingredients provide more) | The percentage depends on whether it is magnesium malate or dimagnesium malate |
Why are these figures only approximate?
Magnesium glycinate, citrate and malate can come in slightly different chemical versions. Some also contain water molecules as part of their structure. This adds to the total weight of the compound without adding more magnesium, so the percentage of elemental magnesium becomes lower.
Why can two supplements using the same form provide different amounts?
You may find two magnesium glycinate supplements that provide very different amounts of elemental magnesium. One brand may simply use more magnesium glycinate than another.
The serving size can also be different. One product may provide its stated amount in one capsule, while another may require three or four.
Some products also contain a blend of magnesium forms. For example, a supplement sold as magnesium glycinate may also contain magnesium oxide, which can increase the amount of elemental magnesium it provides.
This is why you cannot judge the amount of magnesium from the form alone. You still need to check the elemental magnesium listed on the label.
A higher elemental percentage does not automatically mean a form is better or that your body will absorb more of it. We will look at absorption next.
Does more elemental magnesium mean your body absorbs more?
No. A higher elemental amount means that the supplement contains more magnesium, but it does not tell you how much of it your body will absorb.
The form matters
Before magnesium can be absorbed, it needs to dissolve in your digestive system. Forms that dissolve more easily tend to be absorbed better than forms that do not dissolve as well.
Magnesium oxide is a good example. It contains a high percentage of elemental magnesium, but it does not dissolve particularly well. Studies have found magnesium citrate to be more easily absorbed than magnesium oxide, even though citrate contains a much lower percentage of elemental magnesium.
This means that a supplement with a bigger elemental magnesium number is not always the one that gives your body the most usable magnesium.
Your digestion matters too
The amount you take and how well you tolerate it can also make a difference. When some of the magnesium remains unabsorbed in your bowel, it draws in water and may cause loose stools or diarrhoea.
Certain digestive conditions can also reduce magnesium absorption. Age may play a part too, as absorption from the gut can decrease as we get older.
So, when comparing supplements, look at both the elemental amount and the magnesium form rather than choosing the product with the largest number.
How much magnesium do you need each day?
Once you know how much elemental magnesium a supplement provides, the next question is how much magnesium you actually need.
The recommended amounts differ slightly between the UK and the US.
UK recommendations
| Adults aged 19 to 64 | Magnesium per day |
|---|---|
| Men | 300 mg |
| Women | 270 mg |
US recommendations
| Adults | Magnesium per day |
|---|---|
| Men aged 19 to 30 | 400 mg |
| Men aged 31 and over | 420 mg |
| Women aged 19 to 30 | 310 mg |
| Women aged 31 and over | 320 mg |
The UK and US use different methods to set their recommendations, which is why the figures are not the same. Magnesium needs may also change during pregnancy and at other stages of life.
Your daily requirement is not your supplement dose
These recommendations refer to your total magnesium intake, including magnesium from food and any supplements you take. They do not mean that you need to get the full amount from a supplement.
Foods such as nuts, seeds, beans, whole grains and leafy green vegetables already contribute towards your daily intake. A supplement simply adds to the magnesium you get from your diet.
For example, if you get around 220 mg from food and take a supplement providing 100 mg of elemental magnesium, your total intake would be around 320 mg.
How much elemental magnesium should you take?
There is no single dose that is right for everyone. If you simply want to top up the magnesium you get from food, around 100 to 200 mg of elemental magnesium per day can be a sensible starting range for many adults. This is not a fixed recommendation, and you may need more, less or no supplement at all.
The right amount depends on how much magnesium you get from food, why you are taking it, your age, your health and how well you tolerate the supplement.
The form matters too. Two supplements may both provide 200 mg of elemental magnesium, but one may be absorbed or tolerated better than the other. This is why you should not choose a supplement based on the elemental amount alone.
Higher or more specific doses may be used for a diagnosed deficiency, migraine, constipation or another medical reason, but these should be considered separately and may require advice from a doctor or pharmacist.
How much elemental magnesium is too much?
There is no single maximum dose that is right for everyone, but official guidance gives us useful safety limits for magnesium from supplements.
In the US, the upper limit for adults is 350 mg of elemental magnesium per day from supplements and medicines. In the UK, the NHS says that 400 mg or less per day from supplements is unlikely to cause harm. These amounts do not include magnesium naturally found in food.
These figures refer to the actual magnesium shown on the label. For example, if a supplement provides 200 mg of magnesium from magnesium glycinate, that counts as 200 mg towards the limit, not the total weight of the magnesium glycinate compound.
These limits are not recommended doses or a precise point at which magnesium suddenly becomes dangerous. They are general safety guidelines, and higher doses are sometimes used for a specific medical reason under professional advice.
Taking more magnesium than your body can tolerate commonly causes diarrhoea, nausea and stomach cramps. People with kidney problems should be particularly careful because their bodies may not remove excess magnesium effectively.
Final takeaway
The main thing I want you to remember is not to be impressed by the biggest number on the front of the bottle. Turn it around and check how much magnesium the supplement actually provides and how many capsules you need to take to get it.
Once you understand elemental magnesium, labels become much easier to compare and you are less likely to buy a supplement that is not quite what it first appears to be.
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