A supplement label is a short document with a lot of hiding places. Most of the marketing happens on the front; almost everything that matters is on the back, in six numbers. Here is what each one tells you, and what its absence tells you.
1. Serving size — and servings per container
The first number to find, because every other figure on the panel is relative to it. Two capsules per serving and sixty capsules in the bottle is a thirty-day supply, not a sixty-day one, and the per-bottle price you are comparing is therefore double what it looked like. This is the most common way a price comparison goes wrong.
2. The amount beside each ingredient
Every active should carry a number. If several ingredients share one total under a heading like "proprietary blend" or "botanical complex", you cannot know how much of anything you are getting — and the reason that structure exists is almost never to protect a formula from being copied.
Where amounts are listed, the order is by weight, heaviest first. An ingredient near the bottom of a long list is present in a small amount, whatever the front of the bottle says about it.
3. Standardisation, on plant extracts
"Green tea extract 500 mg" and "green tea extract 500 mg, standardised to 50% EGCG" are different products at the same weight. Standardisation tells you how much of the active compound is actually in there. A botanical listed without it is an unknown quantity, and the research you have read about that plant may not apply to what is in the bottle.
4. Percent daily value
Only vitamins and minerals carry one, and it is worth a glance for the opposite of the usual reason: very high percentages are not automatically better. Several nutrients have upper intake levels, and a formula at 2,000% of anything is making a marketing point rather than a nutritional one.
5. Caffeine, declared or implied
Added caffeine has to be declared. Caffeine that arrives inside a plant extract — green tea, guarana, yerba mate, kola nut — frequently is not quantified anywhere on the panel. If any of those appear in the ingredient list, the product contains caffeine whether or not the word appears, and you should count it against your daily total.
6. The lot number and expiry date
The least glamorous pair on the label and the most useful in a problem. A lot number means the manufacturer can trace a specific production run, which is what a recall depends on. A bottle without either is a bottle nobody is prepared to be accountable for.
What is not on the label
Whether it works. Supplement labels in the United States carry structure and function statements, not efficacy claims, and they all carry the same disclaimer saying the FDA has not evaluated any of it. That is not a loophole or a formality — it is the actual regulatory position, and it applies to every product in the category including the one this site is about.