How we compare
Cost per dose
Bottle price is close to meaningless in this market. A $12 magnesium bottle that needs four capsules to reach a real dose costs more per dose than a $20 bottle that needs one. So we convert everything to a single comparison unit per category and divide.
Two adjustments matter more than people expect. First, we compare on the active substance, not the compound: magnesium glycinate labels usually print the weight of the whole compound, of which roughly 14% is actually magnesium, and fish oil labels print total oil rather than the EPA and DHA that trials studied.
“If you just want one answer”
Most people do not want to read a table. So each category names one product — but it is a rule, not a score, and the rule is published so you can disagree with it. There are no weightings inside it to argue about.
A product must clear three factual bars: an independent certification we could confirm covers that exact package, a delivery cost we actually know, and no recall, warning letter or failed test in the sources we checked. Among everything that clears all three, the cheapest per delivered dose wins. That is the whole calculation. A clean record here means we found nothing against the product, not that nothing exists — see below.
Underneath it we list the cheaper products that fail exactly one bar, and name which one — showing a different trade-off each time rather than the same one twice. A certified product that fails only because its retailer will not publish a delivery rate is a very different proposition from an uncertified one, and you may well judge those differently to us. That is the point of showing them.
We also flag products that fail only because delivery is not free, and only just — a product a penny short of a free-delivery threshold is not a worse buy, it is a basket you have not finished. A rule cannot see that. A person can, so we say it rather than letting the arithmetic quietly rule out a better product.
Delivery
A price without delivery is not a price. A cheaper tub from a retailer whose free-delivery threshold is $59 can cost more than a dearer one from a retailer whose threshold is $25, and a comparison that ignores this quietly gets the ranking backwards.
Where a retailer publishes its rate, or the order qualifies for free delivery, we include it. Where it does not — several calculate delivery at checkout from weight and destination — we say the cost applies, say we do not know it, and refuse to invent a figure. Such a product can still appear in the table, but it cannot hold a “cheapest” badge on a price that is missing a charge you will actually pay. We also show how much more you would need to spend to cross the free-delivery threshold, because that is usually the useful thing to know.
When a product is excluded from a “cheapest” badge for that reason and might still be the better buy, we name it and say so, rather than letting it disappear.
Pill burden
We also show how many capsules, softgels or scoops it takes to reach the comparison unit, and flag products where that is not a whole number. We do not fold this into the price. Rounding up to a whole capsule changes the dose you receive as well as what you pay, so charging a product for it would penalise concentrated products for being concentrated. It is a caveat you can see, not an adjustment we make on your behalf.
The comparison unit is not a recommendation
Each category has one comparison unit, chosen so that products of different strengths land on the same scale. It is a yardstick for price. It is not advice about what you should take, and we do not tailor it to you. Every comparison unit is published with the reference we took it from:
Verification levels
We do not publish a quality score, because we cannot defend the weightings such a score would require. What we can defend is a statement about which documents exist for a product and who produced them. Each level below is checkable by clicking through to the source.
This exact product appears in the public database of NSF Certified for Sport or USP Verified. Both audit the manufacturing site and both confirm the label’s own claims against the finished product, which is the part tier B programs do not reliably do. They are not interchangeable beyond that: NSF Certified for Sport also screens for substances banned in sport, and USP Verified does not — USP instead checks that the product dissolves and releases within a specified time. What was actually tested is set out per program below.
A third party with no commercial stake in the product has tested it and published the result — Informed Sport, Informed Choice, BSCG, or an independent laboratory. What that testing covers varies by program and is not always what you would assume: Informed Sport and Informed Choice screen finished batches for substances banned in sport and review manufacturing procedures on paper, which is not the same as confirming the label’s dose or testing for heavy metals. The listings below say which program this is, so you can check what it actually covers.
The only testing information available comes from the manufacturer or a lab it commissioned. This may well be accurate; it is simply not independent.
We could not locate independent testing or certification for this product. That is a statement about our search, not about the product: most supplements sold have never been independently tested, so this mostly means nobody has looked. Which certifier databases we searched, and when, is listed below — where a program is not listed there, we have not checked it and do not imply anything either way.
Recalls and warning letters affecting the product you are looking at are shown as a warning. Actions affecting a brand's other products are listed separately under brand history, without a warning badge — almost every large brand has had something recalled eventually, and badging those would penalise size rather than sloppiness.
A Tier D product is not a bad product. The large majority of supplements sold have never been independently tested, so Tier D mostly tells you that nobody has looked. Recalls, warning letters and failed tests are listed separately and never folded into the level. Where we list none, that means none has reached us — not that we have run an exhaustive search and cleared the product.
Money
As of 27 August 2026 no link on this site earns us anything. We have applied to affiliate programs at iHerb and BulkSupplements; neither is live, so every purchase link is a plain retailer URL. Each link says what it earns us, and will keep saying so when that changes.
No commission, of any size, affects which products we list, how they rank, what verification level they receive, or what we write about them. Rankings are computed from the data by the same code for every product. If we ever accept paid placement it will be visually separate from the comparison and labeled as advertising.
Four separate decisions are worth pulling apart, because they are not equally protected. Which product ranks first, and which retailer link we send you to, are never influenced by what we earn — the Buy button points at the lowest price we have recorded even when that retailer pays us nothing, and every link is labeled so you can check. Which retailers we track, and which categories we build first, are influenced by commercial reality, because we have finite time. Those affect what the site covers, not what it tells you.
The failure we are most alert to is bias by omission: quietly tracking only the retailers that pay, so that every page is technically true while the site systematically shows worse prices. The defense is that we record every retailer price we can find, including retailers with no affiliate relationship at all, and a check runs on every build confirming that each Buy button points at the cheapest listing on record.
What we will not do
- Infer a fact we have not read from a source. Unknown stays Unknown.
- Treat absence of contaminant data as evidence a product is clean.
- Tell you what to take for a medical condition.
- Reprint a manufacturer's marketing claim as though it were a test result.