Why elemental magnesium matters
Magnesium supplements are never sold as pure magnesium metal. They are always a compound — magnesium bound to another molecule such as oxide, citrate, or glycine. The label might say "Magnesium Citrate 400mg," but that is 400mg of the compound, not 400mg of elemental magnesium. The fraction of actual magnesium inside the compound varies dramatically by form, and that fraction is what determines how much you pay per effective dose.
What is elemental magnesium?
Elemental magnesium is the actual magnesium ion (Mg2+) inside a supplement compound. It is the part your body can absorb. The rest of the compound — the oxide, citrate, glycinate, or other carrier molecule — adds weight to the pill or powder but does not contribute to the magnesium dose.
Think of it like buying coffee beans. A 1kg bag contains the beans plus the bag itself. The bag is necessary but you do not drink it. In magnesium supplements, the carrier molecule is the bag, and the elemental magnesium is the beans.
Different forms have different “bean-to-bag” ratios. This is called the elemental fraction.
Elemental fractions by form
The table below shows the approximate percentage of elemental magnesium in each common supplement form. These percentages are based on the molecular weight of the compound:
| Form | Compound formula | Elemental Mg fraction | What that means |
|---|---|---|---|
| Oxide | MgO | ~60% | Highest weight fraction. 400mg of magnesium oxide yields ~240mg elemental magnesium. Often the cheapest per gram of elemental but has a different solubility profile. |
| Citrate | Mg(C6H6O7) | ~16% | Common, mid-range form. 400mg of magnesium citrate yields ~64mg elemental magnesium. Good solubility. |
| Bisglycinate | Mg(C2H4NO2)2 | ~18% | Amino acid chelate. 400mg of magnesium bisglycinate yields ~72mg elemental magnesium. Often positioned as a premium form. |
| Glycinate | Mg(C2H4NO2)2 | ~14% | Similar to bisglycinate but lower elemental fraction. 400mg yields ~56mg elemental. |
| Malate | Mg(C4H4O5) | ~15% | Malic acid salt. 400mg yields ~60mg elemental magnesium. |
| Taurate | Mg(C2H7NO3S)2 | ~9% | Taurine-bound. 400mg yields ~36mg elemental. Lower fraction means more compound weight to reach a given elemental dose. |
These fractions reflect the chemistry of each compound. They are not opinions about which form is better. The fraction tells you how much elemental magnesium you get per gram of product purchased.
How DosePrice normalizes magnesium prices
DosePrice detects which magnesium form each product uses and applies the corresponding elemental fraction. The engine then computes:
EUR per 100mg elemental = (total known price) / (total elemental magnesium in the package, in 100mg units)
This calculation accounts for the different elemental fractions automatically, so a magnesium oxide product and a magnesium bisglycinate product can be ranked side by side on the same EUR-per-effective-dose scale.
When the label states elemental content directly (e.g., “providing 100mg elemental magnesium”), DosePrice uses that stated value. When the label only states compound weight, the engine computes elemental content from the form-specific fraction.
Products with an unknown form, missing weight, or unparseable label are marked low confidence and excluded from the main ranking.
How to read a magnesium label
Magnesium supplement labels follow two common patterns:
- Compound-first: The label states the compound weight, e.g., “Magnesium Citrate 400mg,” and may or may not also state the elemental amount. If the elemental amount is not stated, DosePrice computes it from the compound fraction.
- Element-first: The label states the elemental amount directly, e.g., “Magnesium (from Magnesium Citrate) 100mg,” and the compound weight may be listed in parentheses or not at all. This is the consumer-friendly approach.
When comparing two products, always check whether the dose shown is the compound weight or the elemental weight. Two products both labelled “400mg Magnesium” could mean very different things if one refers to elemental and the other to the compound.
Why oxide is often the cheapest per effective dose
Magnesium oxide has the highest elemental fraction (~60%) of any common form. This means less compound weight is needed to deliver a given elemental dose. Combined with the fact that oxide is inexpensive to manufacture, this makes magnesium oxide products the lowest cost per 100mg elemental in most markets.
However, magnesium oxide has different solubility properties compared to citrate or bisglycinate. The ranking on DosePrice reflects price per effective dose only. It does not rank by solubility, absorption kinetics, or any other property. Which form is appropriate for you is a question for a healthcare professional.
If you have a preference for a specific form, you can browse by form on the magnesium form comparison page to see prices segmented by citrate, bisglycinate, oxide, and other forms individually.
Putting it into practice
- Visit the magnesium ranking page to see all products sorted by EUR per 100mg elemental magnesium.
- Use the form comparison page to browse products grouped by form (citrate, bisglycinate, oxide, etc.).
- Click any product to see its individual offers, shipping options, and price history.
- Pick two products and compare them side by side on the product comparison page.
This guide describes the chemistry and pricing of magnesium supplement forms. It does not provide medical advice. Consult a healthcare professional about which form is appropriate for you.
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