How to read a UK food label

Front of pack: the traffic lights

Most UK products carry colour-coded labels on the front, usually for energy plus four nutrients: fat, saturated fat, sugars and salt. The colours are a quick shorthand: red means high, amber means medium, green means low.

The NHS puts it simply: a food or drink that has "all or mostly green on the label is a healthier choice," while "any red on the label means the food is high in fat, saturated fat, salt or sugars, and you should limit your intake." A red here and there is fine in the context of a balanced diet — the label is a guide, not a verdict — but a wall of red is a signal to eat that product less often.

What counts as "high" and "low"

The colours aren't arbitrary. They're based on how much of each nutrient is in 100g of the product. These are the NHS thresholds:

You don't need to memorise these — but they explain why, say, a cereal can look "healthy" on the front and still be red for sugar.

Reference intakes (the %RI)

You'll also see reference intakes, shown as a percentage. The British Heart Foundation describes RIs as "useful guidelines on the amount of energy and nutrients you need for a healthy, balanced diet each day." They're based on an average adult, so they won't match everyone, but they're handy for a sense of proportion. The reference amounts used on labels are:

• Energy: 2,000 kcal
• Fat: 70g
• Saturates: 20g
• Sugars: 90g (total)
• Salt: 6g

Salt is the one most of us get wrong. As the BHF notes, "most adults eat more salt than the recommended maximum of 6g a day," which raises the risk of high blood pressure. One tip: if a label lists sodium instead of salt, multiply it by 2.5 to get the salt figure.

Per portion vs per 100g

Nutrition tables often show two columns: per portion and per 100g. The per-portion figure can be flattering, because the manufacturer chooses the portion size — a "portion" of crisps might be half the bag. When you're comparing two products, use the per 100g column: it's the fair, like-for-like number, and it's the same basis the traffic lights use.

The ingredients list

Ingredients are listed in order of weight, from most to least. That single rule tells you a lot: if sugar (or one of its many aliases) is near the top, there's a lot of it; if the first ingredient in a "chicken" ready meal is water, that's worth knowing. Additives appear here too, by name or E-number — our guide to food additives and E-numbers explains which are worth a second look.

Allergens and Natasha's Law

UK law requires 14 allergens to be declared whenever they're used as ingredients, and emphasised in the list — typically in bold, but capitals, underlining or a contrasting colour are also allowed. The 14 are:

celery · cereals containing gluten (such as wheat, rye, barley and oats) · crustaceans · eggs · fish · lupin · milk · molluscs · mustard · peanuts · sesame · soybeans · sulphur dioxide and sulphites (above 10 mg/kg or 10 mg/litre) · tree nuts.

Since 1 October 2021, the rules known as "Natasha's Law" also require food that is prepacked for direct sale (PPDS) — think a sandwich made and wrapped on site — to carry a full ingredients list with those 14 allergens emphasised. The law was introduced after the death of Natasha Ednan-Laperouse, who reacted to a baguette that didn't have to be labelled at the time.

If you have an allergy, the label is the authority. Apps and databases — Scrannr included — can help you spot allergens quickly, but the data can be incomplete. Always read the on-pack label before you buy or eat.

Use-by vs best-before

One last thing that trips people up. A use-by date is about safety: don't eat the food after it, even if it looks and smells fine. A best-before date is about quality: the food is usually still safe afterwards, it just may not be at its best. Knowing the difference cuts both risk and food waste.

That's the whole label. Scrannr does this read for you in a second: scan a barcode and it surfaces the nutrition, allergens on file and additive flags, and rolls them into a single health score so you can compare products without turning every packet over.

Not medical advice. This guide is general information, checked against NHS, British Heart Foundation and Food Standards Agency guidance. Reference intakes are based on an average adult and won't suit everyone. If you have a food allergy or a health condition, read the product label and speak to a qualified professional.