You flip a magnesium pouch over and the front says one number while the back says another. Which one is the magnesium?
It's a stat screen problem. The box art shouts the big flashy figure, and the tooltip tells you the actual stat. The good news is that it's simple maths, and once you've done it you can check any magnesium pack in about thirty seconds. We'd rather you check the numbers than trust a slogan.
Two weights, one capsule
Magnesium doesn't come in a capsule on its own. It's bound to something else: an acid, an amino acid, oxygen. That pairing is called a compound, and the compound gets a name on the label: magnesium bisglycinate, magnesium citrate, magnesium oxide and so on.
So a label can quote two different weights, and both can be correct:
- Compound weight: the whole ingredient, magnesium plus whatever it's bound to.
- Elemental weight: only the magnesium itself.
"Elemental" just means the magnesium on its own, without the weight of the compound it arrives in. That's the number you're hunting for.
The RESPAWN label as a worked example
Here's our own label, because it's the one we can show you the sums for. One daily serving is two capsules.
| On the label | What it is | RESPAWN |
|---|---|---|
| Magnesium bisglycinate | Compound weight | 1,522 mg |
| Magnesium | Elemental weight | 300 mg |
| % NRV | Share of the daily reference value | 80% |
The 1,522 mg is the whole compound. The 300 mg is the magnesium inside it. Divide one by the other (300 ÷ 1,522) and you get roughly 0.2, so about a fifth of that weight is magnesium. The rest is the compound it comes in.
Nothing sneaky about that. Every magnesium compound works this way. The skill is knowing which line you're reading.
What NRV means
NRV stands for nutrient reference value. It's the yardstick a label uses to show how much of a nutrient is in a serving compared with a standard daily reference amount. For magnesium, the NRV is 375 mg.
Here's the sum for RESPAWN: 300 mg ÷ 375 mg = 0.8, which is 80% of the NRV.
Two things worth noticing:
- NRV is worked out from the elemental figure. Divide the compound weight by 375 instead (1,522 ÷ 375) and you'd get about 406%, which tells you straight away you've used the wrong line.
- It's a yardstick for comparing labels, not a score to max out.
Your 30-second check for any pack
- Go to the back. The nutrition table is there, not on the front.
- Find the line that just says "Magnesium". That's the elemental weight, usually with a % NRV beside it.
- Find the form. Look for "magnesium (as …)" or the ingredient name: bisglycinate, citrate, oxide. That's the compound, and its weight may be listed too.
- Check the serving size. Is the figure per capsule, per two capsules, per scoop? Make sure you're comparing like with like.
- Do the sum. Elemental mg ÷ 375 × 100 should give the % NRV on the label. If it does, you're reading the right line.
- Compare per day. Elemental magnesium per daily serving is the fair comparison, whatever size the capsules are.
Three classic mix-ups
- Reading the compound as the magnesium. A big "1,522 mg" next to the ingredient name is the compound. The magnesium is the smaller number on its own line.
- Mixing up serving sizes. RESPAWN's figures are for two capsules, which is one daily serving. Each capsule is half: 761 mg of compound and 150 mg of magnesium. A pack quoting "per capsule" and another quoting "per serving" aren't directly comparable until you convert one.
- Comparing the wrong rows. Elemental against elemental, compound against compound. Never one against the other.
Same trick, different ingredient
The black pepper extract in RESPAWN follows the same logic. The label says 5 mg of black pepper extract, and that extract is 95% piperine. So the piperine itself is 4.75 mg (5 × 0.95).
One line is the weight of the extract. Another is the named ingredient inside it. Same question every time: which line are you reading?
Quick glossary
- Elemental magnesium: the magnesium itself, not counting the compound's weight.
- Compound: magnesium bound to something else, such as glycine, citric acid or oxygen.
- NRV: nutrient reference value, the daily reference amount used to work out the % on a label. 375 mg for magnesium.
- Serving: the amount the label's figures apply to. Check how many capsules that is.
What the wording on the pack can say
Health wording on a UK pack has to come from an authorised list, and it's phrased around the nutrient. Our wording follows the same rule. For example: Magnesium contributes to a reduction of tiredness and fatigue.
Notice the subject of that sentence is magnesium, not "our blend" and not a particular compound. It's another reason the elemental figure is the one to read.
A label is a spec sheet. Read the right line, do the sum, and you know exactly what's in the capsule.