What does per serving vs per capsule mean on a label?

The three numbers, and why a label can quote any of them honestly and still mislead

Per serving and per capsule are two of three numbers a supplement label can quote, and confusing them is the commonest arithmetic error on the shelf, so define all three. Per capsule: the amount of the active in one capsule, tablet or softgel, a true figure and the one a front label prefers when a serving is two or three, because 500mg per capsule reads better than the serving's real story. Per serving: the amount in the number of capsules the label defines as one serving, the UK supplement table's required basis being per recommended daily portion, so that on a compliant UK label the table is already per serving and the serving is what the label directs, two capsules on the worked example. Per daily dose: the amount actually taken in a day, which equals per serving where the label directs one serving a day and is a multiple where it directs two or three, a fish oil directing one softgel three times a day delivering three servings' worth, and the American Supplement Facts panel's serving size and servings per container needing the same multiplication. A label can quote any of the three honestly, and the misleading move is mixing them: a front label quoting per capsule beside a competitor's per-serving table, a claim tied to a per-day amount printed beside a per-capsule figure, or a price quoted per bottle for a product whose daily dose empties the bottle in a month, each true in its own number and false in the comparison.

The worked examples that reconcile them, and the one number everything runs on

Three worked examples reconcile the numbers. A magnesium citrate labelled 500mg per capsule, three capsules a day: 500mg per capsule is compound weight, so the elemental magnesium is around 80mg per capsule, the per-serving figure is three capsules and around 240mg elemental, the per-daily-dose figure is the same 240mg because one serving is a day, and the bottle of 90 capsules is 30 days, so the comparison with the worked example's 300mg elemental per two capsules, 90 days from 180, is 240 against 300 elemental and 30 days against 90, whatever the front says. A fish oil labelled 1000mg per softgel, one softgel three times daily: per softgel is the oil weight, the EPA and DHA per softgel may be 300mg, the per-serving figure is one softgel, the per-daily-dose figure is three softgels and 900mg of EPA and DHA, and the 90-softgel bottle is 30 days, the daily dose being the number the heart-function claim at 250mg and the cost per day both need. A mushroom extract labelled 1500mg equivalent per capsule, one capsule daily: per capsule, per serving and per daily dose coincide, the simplest case, and the only arithmetic is the ratio behind the equivalent. The one number everything runs on is the daily dose at the label's direction: the authorised claims attach to daily amounts, so a claim is checked per day; the %NRV is declared per daily dose on a UK label; the cost per day divides the price by the daily doses in the bottle, count over capsules per day; and every comparison between two products is per daily dose or it is not a comparison, the worked example's two capsules being one serving and one daily dose, 300mg elemental at 80% NRV, 90 days, 22p, the three numbers agreeing because the label was written to be read.

The verdict, three numbers and one that matters

What does per serving versus per capsule mean on a label: per capsule is one capsule's contents, per serving is the label's defined number of capsules and a UK table's basis, and per daily dose is what is taken in a day, one serving or several, with the elemental figure and the bottle's day count riding on the same arithmetic and every claim, %NRV and price comparison running on the daily dose at the label's direction. The label where the three agree: Futuro Labs Magnesium Glycinate, two capsules, one serving, one daily dose, 300mg elemental at 80% NRV, 90 days from 180 capsules, £19.99 at 22p a day.

What to check on the label

Questions people also ask

Is per serving the same as per capsule?

Only when the serving is one capsule: per serving is the amount in the number of capsules the label defines as a serving, and a UK supplement table's figures are per recommended daily portion, which may be two or three capsules.

Is per serving the same as per day?

Only when the label directs one serving a day: a fish oil directing one softgel three times daily delivers three servings a day, and the daily dose is the number claims, %NRV and cost per day run on.

Why do front labels quote per capsule?

Because 500mg per capsule reads better than the serving's real story when the serving is three capsules and the elemental figure is a fifth of the compound, the comparison being false while each number is true.

How do I compare two supplements fairly?

Per daily dose at each label's direction: the elemental or extract amount taken in a day, the %NRV per day, and the price divided by the number of daily doses in the bottle.

How many days does a bottle last?

Capsules in the bottle divided by capsules per day: 180 at 2 a day is 90 days, 90 at 3 a day is 30, and the bottle price means nothing until it is divided by that number.

Sources

1. The retained Food Information to Consumers regulation: the mandatory nutrition declaration for foods, its fixed order of energy, fat, saturates, carbohydrate, sugars, protein and salt per 100g, and its rules on portion information, with supplements declaring nutrients per daily dose against nutrient reference values. https://www.legislation.gov.uk/eur/2011/1169/contents
2. Retained Regulation (EU) No 1169/2011, Annex XIII: nutrient reference value for magnesium 375mg. https://www.legislation.gov.uk/eur/2011/1169/annex/XIII
3. The Food Supplements (England) Regulations 2003. https://www.legislation.gov.uk/uksi/2003/1387/contents/made
4. The GB claims register, magnesium entries: magnesium contributes to a reduction of tiredness and fatigue, normal psychological function, normal nervous system function, normal muscle function and electrolyte balance, among others. https://www.gov.uk/government/publications/great-britain-nutrition-and-health-claims-nhc-register

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