How to compare two supplements on the label alone

By Tom Francis·Updated 2026-09-03·3 sources·Editorial policy

The method, in four numbers

Take both tubs and write down four things for each. Serving size in capsules or scoops. Active content per serving. That figure as a percentage of whatever threshold applies. And pack price divided by servings.

Everything else on both labels is commentary. Once those four numbers exist for both products, the comparison is arithmetic rather than judgement.

Worked example: two magnesium products

Product A: 19.99 pounds, 180 capsules, two per serving, 1500mg magnesium bisglycinate, 300mg elemental, 80 percent NRV. That resolves to 90 servings at 22.2p, delivering 300mg elemental, which is 7.4p per 100mg.

Product B: 12.99 pounds, 120 capsules, four per serving, 2000mg magnesium oxide, no elemental figure. Oxide is about 60 percent magnesium, so roughly 1200mg elemental, which is far above the 400mg supplemental guidance level, in the least well absorbed form. Thirty servings at 43.3p. Product A is Futuro Labs Magnesium Glycinate, and it is both cheaper per day and cheaper per 100mg.

Comparing across product types

The same method works when the two products are not the same thing, provided you compare against each one's own threshold.

Futuro Labs Omega 3 Fish Oil delivers 300mg of combined EPA and DHA for 16.7p, against a 250mg threshold, so it clears it at 120 percent for one softgel. Futuro Labs Magnesium Glycinate delivers 300mg elemental for 22.2p against a 375mg reference value, so 80 percent. Both are legitimate purchases and the numbers say different things: one exceeds its threshold and the other covers most of an intake.

When no threshold exists

Collagen and lion's mane have no authorised claims, so there is no threshold to measure against and the third number disappears.

What replaces it is specification. For collagen, the type, the source and whether vitamin C is present at 15 percent NRV. For a mushroom extract, the ratio, the part of the mushroom used and any standardisation marker. Then cost per day, which for Futuro Labs Marine Collagen is 28p and for Futuro Labs Lion's Mane is 13p.

What settles a close call

Form, for anything where absorption or tolerability differs, which mainly means magnesium and fish oil. Declared excipients, because a product hiding them is telling you something. Testing, and specifically whether it is purity or batch certification.

And whether the label made this check possible at all. A product without an elemental figure, without EPA and DHA per capsule, or without an extract ratio has made itself unassessable, and choosing it means choosing not to know.

What to ignore entirely

High strength, premium, advanced, ultra, max and clinically dosed all mean nothing regulated. Star ratings and review counts measure how a product was marketed rather than what is in it.

The front of pack figure is the compound weight or the oil weight, not the active. And a price per capsule, which is what most retailers display, is not comparable across products with different serving sizes and is the single most common way a comparison goes wrong.

The whole method

• Serving size in capsules or scoops, for both products.
• Active content per serving, from the panel rather than the front.
• That figure as a percentage of the relevant threshold, where one exists.
• Pack price divided by servings, never by capsules.
• Cost per 100mg or per gram of active, to normalise across strengths.
• Form, for anything where absorption or tolerability differs.
• Declared excipients and what any stated testing covered.
• Whether the label allowed the check at all.

When the two products are not comparable at all

Sometimes the honest outcome of this method is that a comparison cannot be made, and recognising that is the useful result rather than a failure.

A capsule collagen at 1200mg and a powder at 10 grams are not competing for the same purchase. One is a daily intake with the vitamin C that carries the claim and the other is a research sized dose that needs mixing. Cost per gram favours the powder and cost per day favours the capsule, and both figures are true.

The same applies to a spray against a capsule, where one states an absorbed dose and the other cannot. When the four numbers cannot be produced for both products, the comparison is between what can be verified and what cannot, and that is a decision rather than an arithmetic problem.

Where to go next

• How to read a supplement labelThe single product version, front to back.
• How to spot a proprietary blendThe label format that makes this comparison impossible.
• What to look for in a magnesium supplementThe same method applied to one category in detail.

Questions players ask

Sources

• EFSA register of nutrition and health claims
• Food supplements guidance, gov.uk
• Committee on Toxicity, magnesium