Most men buy a supplement by reading the front of the bottle. The front of the bottle is marketing. The Supplement Facts panel on the back is the part that's regulated, and it's the part that tells you whether you're being sold something or sold to.
Here's how to read it in about ninety seconds.
1. Start with serving size, not the big number
The panel's amounts are per serving, not per capsule. If the front says 1,000 mg and the serving size is three capsules, each capsule holds about 333 mg. A 60-capsule bottle at three per serving is a 20-day supply, not a two-month one.
This is the single most common way a price comparison goes wrong. Two bottles at the same price aren't the same value if one makes you take three times as many capsules to hit the same dose.
2. Check the form, not just the name
"Magnesium 500 mg" tells you almost nothing on its own. Magnesium oxide, citrate and glycinate behave very differently in terms of absorption and stomach comfort, and the cheapest form is cheap for a reason.
The same applies elsewhere. An extract's potency depends on its ratio and standardisation — a 10:1 extract and a raw powder at the same milligram figure are not equivalent, and a good label will say which one you're getting.
3. Look for the number that isn't there
This is the big one. If you see a line like "Proprietary Blend — 850 mg" followed by a list of five ingredients with no individual amounts, you have been told the total and nothing else.
Ingredients are required to be listed in descending order by weight. So a blend leading with an inexpensive filler and ending with the ingredient you actually came for tells you the expensive one is present in the smallest quantity — possibly a few milligrams. The industry term for this is fairy dusting, and the proprietary blend is the mechanism that makes it possible.
Manufacturers defend blends as protecting a formula from copycats. It's worth noticing that this argument only ever protects the manufacturer, never the buyer.
4. Compare the dose to the research, not to the competition
An ingredient at 1/10th of its studied amount isn't a smaller version of the effect. It may be no version of the effect. Before you buy anything, search the ingredient plus "dose" and see what amount the human trials actually used, then check the panel against it.
If the label won't tell you the amount, you can't run this check. That's usually the point.
5. Read the "Other Ingredients" line
Below the panel sits a line most people skip. It lists capsule material, flow agents, fillers and anything else that isn't an active. It's also where allergen statements live — glucosamine is frequently shellfish-derived, for instance, and that fact appears here rather than on the front.
6. Remember what the panel can't tell you
A Supplement Facts panel is a claim about what's in the bottle. It is not proof.
The proof is a certificate of analysis: an independent laboratory's confirmation that the ingredient is what the label says (identity), at the amount the label says (potency), without contaminants. A brand that publishes those certificates is letting you verify the panel. A brand that offers them "on request" is asking you to take the panel on faith.
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.