Medical Disclaimer
This site is not medical advice and is not a substitute for a clinician. It summarises published research, reads what supplement labels declare, and compares what products cost. It cannot examine you, it does not know your medical history or medications, and it cannot tell you what you personally should take.
What we do
Three things, and it is worth being precise about which is which, because they carry very different weight:
- We summarise published research. Where we cite a trial or a systematic review we give the PubMed identifier so you can read the original rather than take our reading of it. Where the evidence is weak, contested, or measured only in a specific population, we try to say so on the page rather than round it into a recommendation.
- We read labels. Our dose figures come from the Supplement Facts panel as filed with the NIH Dietary Supplement Label Database, not from marketing copy. When we report a market-wide figure, the sample size and retrieval date are on the page.
- We compare prices. Cost per day is calculated at the dose a label directs, or at the dose used in the trials where we say so. Prices change constantly; the retailer's price at checkout is the one that counts.
What we do not do
We do not diagnose, treat, or prescribe. We do not know whether you are deficient in anything — that generally requires a blood test, and several of our guides say so explicitly because it is the honest answer to “how much should I take”.
Nothing here should be used to start, stop, or change a prescribed medication. Where we describe a drug–nutrient interaction, that is a prompt to raise it with your prescriber, not an instruction to act on. Some interactions are genuinely serious.
Situations where you should talk to a clinician first
- You are pregnant, trying to conceive, or breastfeeding.
- You take prescription medication — particularly anticoagulants such as warfarin, thyroid medication, or anything with a narrow therapeutic range.
- You have kidney or liver disease, which changes how supplements are cleared.
- You are giving a supplement to a child.
- You are considering a dose above a published tolerable upper intake level, or one intended to correct a deficiency you have not had confirmed.
- You have symptoms you are hoping a supplement will fix. Symptoms deserve a diagnosis first.
Limits of the data itself
Our label figures describe what manufacturers declare, not what independent testing confirms is in the bottle, except where we say a product appears in a certifier's registry. Our market-wide censuses count labels on the market, not purchases — so they describe what is on offer rather than what people take. Adverse-event counts we cite from the FDA are voluntary reports with no denominator, and they scale with how many people take a thing rather than with how risky it is.
Where a figure did not survive our own validation checks, we exclude it and say so on the page rather than publishing it with a caveat. If you find a number here you cannot trace to a stated source, that is a bug — please tell us and it will appear on the corrections log.
Affiliate relationships
Some links on this site are affiliate links, and we may earn a commission from purchases made through them at no additional cost to you. Rankings are determined by cost per effective dose, third-party verification and published evidence. The commission rate does not vary by which product you choose, and it does not affect the order. Full detail is in our editorial standards.
In short
Use this site to arrive at your doctor's appointment better informed, to understand what a label is and is not telling you, and to avoid paying more for less. Do not use it instead of the appointment.