Reading labels: frequently asked questions
On this page
What are "other ingredients" or excipients?
Excipients are the substances in a supplement besides the active ingredients — things like capsule shells, fillers, coatings and anti-caking agents that hold the product together or help it get made, but are not there for their own effect.
A label usually lists them under a heading such as “other ingredients” after the nutrition panel. Common examples include bulking agents (such as microcrystalline cellulose), capsule shells (gelatine or a vegetarian alternative such as HPMC), anti-caking agents (such as magnesium stearate or silicon dioxide) and coatings or glazing agents on tablets. They are not part of the dose we compare, but they do matter if you are avoiding a specific substance, checking for allergens, or checking whether a product is vegan.
What is magnesium stearate, and does it count towards the magnesium on the label?
Magnesium stearate is a common anti-caking agent, used in tiny amounts to stop capsule or tablet ingredients sticking to manufacturing equipment; it does not count towards the elemental magnesium figure on the label.
It appears in the “other ingredients” list, separate from the nutrition panel, because manufacturers do not intend it as a source of the mineral, and the amount used per capsule is small compared with a magnesium supplement’s actual dose. If a product’s only magnesium comes from the compound named in the nutrition panel — such as citrate, glycinate or oxide — that is the figure we read and convert; magnesium stearate in the ingredients list is not added to it.
What are bulking agents and anti-caking agents?
Bulking agents add volume to a capsule or tablet so a small amount of active ingredient can be handled and dosed accurately; anti-caking agents stop powders sticking together or to manufacturing equipment during production.
Common bulking agents include microcrystalline cellulose and dicalcium phosphate; common anti-caking agents include magnesium stearate, silicon dioxide and stearic acid. Both are excipients, listed separately from the active ingredients in a product’s “other ingredients”, and are used in small, standard amounts across the industry rather than being specific to any one brand. They do not count towards the dose we compare, but they can matter if you are checking a label for a specific ingredient you want to avoid.
What is the difference between a tablet, a capsule, a softgel, a gummy and a powder on the label?
These describe the physical form the dose comes in, not the ingredient inside it.
A tablet is compressed powder; a capsule is a shell (usually two halves) filled with powder or granules; a softgel is a single sealed shell filled with liquid or oil; a gummy is a chewable, jelly-like sweet; a powder is loose, usually measured with a scoop.
The form affects how the serving is measured and compared: capsules and tablets are usually counted individually, softgels are common for oils such as fish oil, gummies state a “per gummy” or “per two gummies” amount, and powders state an amount per scoop or per gram. We read whichever unit the label actually uses for its serving, rather than assuming one form.
See pack sizes explained across every form we list.
What are vegan capsules made of? How do I tell if a supplement is vegan or vegetarian from the label?
Vegan capsules are usually made from HPMC (hydroxypropyl methylcellulose), a plant-derived alternative to traditional gelatine capsules, which are made from animal collagen (often bovine or porcine, sometimes fish-derived).
A label states this directly, often as “vegan capsule” or “HPMC capsule” printed near the ingredients, or with a vegan or vegetarian logo. Vegetarian-suitable products may still use non-animal gelling agents without formally claiming “vegan” if another ingredient, such as a fish-oil active or a non-vegan glaze, rules it out. We show dietary claims exactly as printed on the label as “claimed” chips, rather than inferring them ourselves, because getting this wrong on a label we have not verified could mislead someone with a real dietary requirement.
What do "buffered", "chelated", "bisglycinate", "glycinate", "time-release" and "liposomal" mean?
Each describes how a product is formulated, not how much active ingredient it contains — that figure is still read from the nutrition panel.
“Chelated” means a mineral is bound to an organic molecule, often an amino acid, to form a stable compound; “bisglycinate” and “glycinate” name a chelate bound specifically to the amino acid glycine. “Buffered” usually means a mineral or vitamin C salt formulated to be less acidic. “Time-release” means the dose is designed to be absorbed gradually rather than all at once. “Liposomal” means the active is wrapped in a fat-based sphere (a liposome) intended to protect it through digestion. We compare liposomal vitamin C separately from standard forms, since it is sold and priced differently.
See magnesium forms or liposomal vitamin C.
How do I compare an effervescent tablet per dose?
The same way as any other form: by the amount of active ingredient one serving provides, and the pack price divided by the number of servings.
Dissolving in water rather than being swallowed whole does not change that maths.
Effervescent tablets usually state their active content clearly on the panel, the same as a standard tablet, so the amount per serving and the pack size are read the same way. Where a listing gives enough information to confirm the amount per serving and the pack size, we price it exactly like any other form in its class; where it does not, it is shown as unverified rather than guessed.
What does "best before" mean for a supplement?
“Best before” tells you when a product might start to lose quality, rather than a safety cut-off.
For a supplement, that usually means the stated potency of the active ingredients may gradually decline; it differs from a “use by” date, which is about safety, not quality.
UK food labelling guidance describes best before dates as relating to quality: “after the best before date, the food is usually safe to eat but may not be of the same quality” (GOV.UK, Understanding food labelling: best before and use-by dates, checked 22 September 2026). Supplements are almost always dated “best before” rather than “use by”, since the main risk of an old supplement is reduced potency rather than a food-safety hazard.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Source: GOV.UK: Understanding food labelling — best before and use-by dates (checked 22 September 2026)
What is the batch or lot number for?
A batch or lot number identifies the specific production run a product came from, so a manufacturer can trace, and if necessary recall, every pack made in that run without affecting other batches of the same product.
It is printed on the packaging alongside the best-before date, usually as a short code of letters and numbers. It is not something a shopper needs to compare products on, but it is useful information to have to hand if you want to report a fault or a quality concern to the manufacturer or retailer, since it lets them pinpoint exactly which production run is affected rather than the product in general.
See how to report a pricing or listing error on any product we list.
What does the Informed Sport logo mean? What does "tested" mean on PerDose, and how is that different from a claim?
Informed Sport (and the related Informed Choice) is a certification programme that batch-tests supplements for substances banned in sport.
It is aimed at athletes who need assurance a product will not cause an anti-doping failure; a product carrying the logo has been through that testing programme.
On PerDose, a “tested” badge simply repeats a testing claim the label or retailer makes — it is not something we independently verify. We show it because it is a genuine, checkable fact about the product as labelled, the same way we show a claimed dietary flag, but we do not audit certification bodies or confirm a given batch was actually tested. Always check the certifying body’s own product list if testing matters for your use.
See how claimed flags work across our tables.
What does GMP mean?
GMP stands for Good Manufacturing Practice, a set of quality-control standards covering how a product is made, tested and documented, intended to ensure consistency and reduce the risk of contamination or mislabelling.
In the UK, food supplement manufacturers are expected to follow general food hygiene and safety standards, and many additionally hold formal GMP certification (sometimes audited under standards used for food or pharmaceutical manufacturing) as a mark of quality assurance beyond the legal minimum. A “GMP certified” claim on a label or a retailer’s site is a manufacturing-standard claim, not a claim about what the product does — it says nothing about dose, effectiveness or safety of the ingredients themselves.
What does "food supplement" mean legally in the UK?
In UK law, a food supplement is any food intended to supplement the normal diet that is “a concentrated source of a vitamin or mineral or other substance with a nutritional or physiological effect” and is sold in dose form.
This definition comes from the Food Supplements (England) Regulations 2003 (equivalent rules apply across the UK), which also require the product to be labelled “food supplement” and to carry the recommended daily portion and specific warnings. Legally, a food supplement is regulated as a food, not a medicine, provided its labelling and marketing make no claim about acting on a disease.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Source: The Food Supplements (England) Regulations 2003, regulation 2(1) (checked 22 September 2026)
What is the THR logo on a herbal product?
THR stands for Traditional Herbal Registration, a UK scheme for herbal medicines based on a long history of traditional use rather than clinical trial evidence.
A product carrying a THR has been assessed by the MHRA against standards of quality, safety and evidence of traditional use. Every THR product carries a nine-digit registration number starting with the letters “THR” on its packaging (MHRA, Introduction of the Traditional Herbal Registration Certification Mark, checked 22 September 2026), and many also display a certification mark to make this easier to spot. A THR registers the product’s manufacturing and traditional-use evidence, not a claim about what it does for any condition.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Source: MHRA: Introduction of the Traditional Herbal Registration Certification Mark (checked 22 September 2026)
What allergen information must a supplement label carry?
UK food labelling rules require 14 named allergens to be highlighted (in a different font, style or background colour) whenever they are used as an ingredient.
They are: celery, gluten-containing cereals, crustaceans, eggs, fish, lupin, milk, molluscs, mustard, nuts, peanuts, sesame, soya, and sulphur dioxide or sulphites above 10mg per kilogram or litre.
This applies to supplements the same as any other packaged food, so a capsule shell, flavouring or bulking agent that contains one of these allergens must still be listed and highlighted, even in a small amount (GOV.UK, Food labelling and packaging: ingredients list, checked 22 September 2026). A separate “may contain” warning can appear where cross-contamination is a risk rather than a deliberate ingredient.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Source: GOV.UK: Food labelling and packaging — ingredients list (checked 22 September 2026)
What does "sugar-free" mean on a gummy?
“Sugar-free” is a regulated nutrition claim in the UK, only allowed on a label when the product meets a defined maximum sugar content, not just a manufacturer’s own judgement of what counts as low-sugar.
Nutrition claims such as “sugar-free” and health claims are controlled through the Great Britain nutrition and health claims (NHC) register, which “sets out all authorised and rejected nutrition and health claims”; only authorised claims may be used (GOV.UK: Great Britain nutrition and health claims (NHC) register, checked 22 September 2026). A gummy sweetened with a sugar alcohol (such as sorbitol or xylitol) instead of sugar can carry the claim, though sugar alcohols can have their own effects on some people in large amounts.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Source: GOV.UK: Great Britain nutrition and health claims (NHC) register (checked 22 September 2026)
Why do some labels give amounts per two capsules?
Because the manufacturer has set the serving size at two capsules rather than one.
This is often done to fit a larger total dose into two smaller, easier-to-swallow capsules rather than one large one, or simply because that is the amount a typical serving of that ingredient requires.
This means the “500 mg per serving” on such a label is split across two capsules, at 250 mg each, so taking only one capsule gives half the stated amount. We always price by the stated serving, not by a single capsule, so a two-capsule serving and a one-capsule serving of the same total dose compare fairly on price per dose even though the capsule counts differ.
See more on what a serving means.
What is a "proprietary blend", and why can it not be priced per dose?
A proprietary blend is a group of ingredients listed together under one combined weight, without stating how much of each individual ingredient it contains.
You can see what is in the blend, but not how much of any one part.
Manufacturers sometimes use blends to protect a formulation from being copied, but it means a key ingredient’s actual amount is not disclosed, only the blend’s total weight and the ingredient order (by law, ingredients are listed by descending weight). Because we can only compute a price per dose from a stated amount, a product where the compound we are pricing sits inside an undisclosed proprietary blend cannot be ranked, and is not shown until the amount is confirmed.
See what is left out and why.
What is the difference between an extract and a powder?
A powder is the dried, ground raw material itself, with nothing removed or concentrated.
An extract has been processed to concentrate specific compounds out of the raw material, so a smaller weight of extract can be roughly equivalent to a much larger weight of the whole herb or plant.
This is why a label might show “root powder 1,500 mg” for one product and “root extract 500 mg (10:1)” for another of the same plant — the extract is more concentrated per gram, even though the number itself is smaller. We compare products within the same class (extract or powder) separately, since a milligram of each is not equivalent.
What does "organic" mean on a supplement label?
“Organic” is a legally controlled term: a product can only be labelled organic if at least 95% of its farm-grown ingredients were produced organically, and the seller is certified by an approved organic control body.
Organic certification covers how the raw ingredients were farmed — without most synthetic pesticides or fertilisers, and following specific animal welfare and environmental standards where relevant — rather than describing anything about the finished supplement’s dose, purity or effect (GOV.UK: Food labelling and packaging — organic food, checked 22 September 2026). A certified organic product must display its control body’s certification, which you can check independently of the brand’s own claim.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Source: GOV.UK: Food labelling and packaging — organic food (checked 22 September 2026)
Why do labels say "may contain"?
“May contain” is a precautionary allergen warning, used when a manufacturer has identified a real risk of accidental allergen cross-contamination.
This can happen through shared equipment, for example, even though the allergen named is not a deliberate ingredient.
UK guidance describes it this way: businesses “should use precautionary allergen labelling (PAL) to warn consumers” when there is “a risk of potential allergen cross-contamination which cannot be controlled”, using specific wording such as “may contain milk” rather than a vague catch-all (GOV.UK: Food labelling and packaging — precautionary allergen labelling, checked 22 September 2026). It should not be used as a substitute for good manufacturing hygiene, and a responsible manufacturer only adds it where a genuine risk exists.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Source: GOV.UK: Food labelling and packaging — precautionary allergen labelling (PAL) (checked 22 September 2026)