Supplement labels, certificates and studies each speak their own vocabulary. On the panel, elemental means the weight of the mineral itself, not of its compound; on a certificate, LOQ is the smallest amount a method can quantify, and <LOQ is not zero; in a study, an SMD of 0.19 sits just below the conventional threshold for a small effect and needs its certainty rating beside it. All 65 terms below are defined that plainly.
The terms are grouped by where they turn up: the Supplement Facts panel, the forms and chemistry behind it, the certificate of analysis, the research, and the rules and intake standards that sit over all three. Each definition is a sentence or two and links to the page on this site that takes it further. Five common questions are answered in full between the groups, and the table below picks out the eight terms most likely to change how a reader judges a product.
| Term | Where you meet it | What it tells you | What it does not |
|---|---|---|---|
| Elemental | The panel | The weight of the mineral itself | Which compound carried it, or how well it is absorbed |
| % Daily Value | The panel | One serving against a reference intake | An upper limit, or whether the dose suits you |
| Proprietary blend | The panel | That several ingredients share one total weight | How much of any one of them is inside |
| Specification | A certificate | What the material was meant to meet | What was found |
| LOQ | A certificate | The smallest amount the method can quantify | Anything about the sample itself |
| Customer of record | A certificate | Who commissioned the document | That the brand selling to you did |
| SMD | A study | How large an effect is, in standard deviations | How certain it is — the GRADE rating beside it does that |
| Structure/function claim | The label | A statement about normal structure or function | That the FDA evaluated it |
Every figure in the definitions comes from a primary document listed under Sources — the federal regulations, FDA guidance, the National Academies, the NIH Office of Dietary Supplements and California’s Proposition 65 agency — or from PubChem arithmetic set out on the forms reference. Words this site does not use about itself are not defined here; the reasons are on the page about one overworked word.
Panel terms
Supplement Facts panel — The boxed label a dietary supplement must carry, laid out by 21 CFR 101.36: serving size, servings per container, each dietary ingredient’s amount per serving, and a % Daily Value wherever one exists. Read it line by line.
Serving size — The amount the label recommends per occasion, in a unit suited to the product: scoops, grams, capsules. Every other figure on the panel is per serving, which is why it is the first line to read. Servings against doses.
Servings per container — Net contents divided by the serving size. It counts servings, not doses: a routine that takes more than one serving at a time empties the container sooner than the number suggests. The division, run on three products.
Amount per serving — The weight of each dietary ingredient in one serving, as the manufacturer declares it. It describes a formula, not a measurement of the container in your hand; only a laboratory document does that. What a laboratory document adds.
Daily Value — The FDA’s reference amount of a nutrient to consume, or not to exceed, each day, used to calculate the % column. Magnesium’s is 420 mg; creatine and collagen have none. Magnesium intake in full.
% Daily Value — One serving’s amount as a share of the Daily Value, rounded to the nearest whole percent. The FDA’s rule of thumb is that 5% or less per serving is low and 20% or more is high. What the column leaves out.
Daily Value not established — The footnote, keyed to a symbol in the % column, that 21 CFR 101.36 requires for dietary ingredients with no Daily Value. It says no reference exists, not that the dose is small. Why the column stands empty.
Dietary ingredient — A substance a supplement is sold to supply: a vitamin, a mineral, an herb or other botanical, an amino acid, or another dietary substance such as creatine. It is declared inside the panel; everything else goes in the list beneath it. How a blend hides one.
Other ingredients — The list printed directly below the panel naming what the container holds besides its declared dietary ingredients — capsule shells, flow agents, fillers, flavourings — without quantities. What the list does and does not say.
Proprietary blend — Several dietary ingredients declared as one total weight, listed in descending order of predominance, with the individual amounts withheld. It is legal under 21 CFR 101.36(c), and it makes the panel impossible to divide. What a blend conceals.
Flow agent — An ingredient that keeps a powder moving through machinery and stops it caking, such as silicon dioxide or magnesium stearate. It belongs in other ingredients, not in the panel. Excipients, explained.
Lot number — The code from which a lot’s complete manufacturing, packaging, labelling and holding history can be determined, under 21 CFR 111.3. A certificate that names a lot describes that lot, not necessarily yours. Which lot a document names.
What does elemental mean on a supplement label?
It means the weight of the mineral itself rather than of the compound carrying it. The federal labelling rule makes the panel declare the element — the weight of calcium, not of calcium carbonate — so “275 mg of magnesium (as magnesium glycinate)” is elemental, while “magnesium glycinate 2,500 mg” is the compound. Divide the first by the second and you have the fraction: here, 11%.
Forms and chemistry
Elemental — The weight of the mineral itself rather than of the compound carrying it. A panel must declare it — the weight of calcium, not of calcium carbonate, in the rule’s own example. Elemental against compound, worked through.
Compound weight — The weight of the whole salt, mineral and partner together. It is always the larger number and the one a front label tends to print: in Night Work, 2,500 mg of magnesium glycinate carries 275 mg of magnesium. Why the bigger number misleads.
Formula weight — The mass of one formula unit of a compound in grams per mole, summed from the atomic weights of its atoms. The active part divided by the whole gives the ceiling a pure compound can reach. Every form, tabled.
Salt — A compound in which a mineral or a molecule is paired with a partner ion, often from an acid, as in magnesium citrate or creatine hydrochloride. The partner sets the fraction, the solubility and often the price. The fractions, form by form.
Chelate — A mineral bound to a molecule at more than one point, as magnesium is held by two glycine molecules in bisglycinate. The word describes a structure, not a measured absorption. What chelated does and does not mean.
Bisglycinate (glycinate) — Magnesium bound to two glycine molecules, 14.1% magnesium by formula weight. Magnesium glycinate, as labels use the word, names the same compound. One word, one compound.
Buffered — A form mixed with an alkaline powder, or one salt blended with another, such as glycinate with oxide. The fraction is then the mixture’s rather than the form’s, which is why a buffered product should be declared as a blend. The buffered creatine trial.
Monohydrate — A crystal holding one water molecule for each molecule of the compound. Creatine monohydrate is 87.9% creatine; the water is the rest. Monohydrate against hydrochloride.
Anhydrous — Without water of crystallisation. Anhydrous creatine is 100% creatine and anhydrous magnesium chloride 25.5% magnesium, against 87.9% and 12.0% for the hydrated forms. How water moves the fraction.
Hydrochloride (HCl) — A salt formed with hydrochloric acid. Creatine hydrochloride is 78.2% creatine and dissolves far more readily than monohydrate, but solubility in a glass is not uptake into muscle. What the trials found.
Ester — A compound made by joining an acid to an alcohol. Creatine ethyl ester is 82.4% creatine by formula weight and was sold on better uptake. What the head-to-head measured.
Micronised — Milled to a finer particle. Micronised creatine is creatine monohydrate with a smaller grain: it disperses more easily, and the molecule and its 87.9% are unchanged. Micronised against regular.
Hydrolysed collagen — Collagen cut by enzymes into short peptides, roughly 3 to 6 kDa in a 2019 review, that dissolve in water and do not set into a gel; sold as collagen peptides. Peptides against gelatin.
Gelatin — Collagen broken down less far than peptides, so that its chains are long enough to set into a gel as it cools. What the difference changes.
Collagen type — One of the numbered members of the collagen family. Type I dominates bone, tendon and ligament, type II cartilage, and type III is most common in muscle and blood vessels. What the numbers mean on a label.
Bioavailability — The share of a dose that reaches the circulation in a form the body can use, measured in people by blood or tissue sampling. A solubility figure is not a bioavailability figure. Absorption studies and their limits.
Certificate terms
Certificate of analysis — A laboratory’s report on a named lot of material: each analyte, the method, the specification and the measured figure, with a date and a signature. How to read one.
Specification — The limit or range a material is meant to meet, set before anything is measured — more than 99.5% creatine monohydrate, for example. A specification with no measured figure beside it is an intention, not a finding. Specification against measured figure.
Assay — A measurement of how much of a named substance a sample contains. It counts quantity; unless the method also identifies the compound, it cannot say which form carried it. Quantity is not identity.
Identity test — A test of whether a material is the substance its label names, usually an infrared or chromatographic fingerprint read against a reference. A quantity figure inherits whatever identity established. Why identity comes first.
Limit of detection (LOD) — The lowest amount of an analyte a method can detect but not necessarily quantify. In FDA’s 2024 guidance, a signal three times the background noise is generally acceptable for estimating it. The four numbers on a metals row.
Limit of quantification (LOQ) — The lowest amount a method can quantify with suitable precision and accuracy; by one accepted approach in FDA’s 2024 guidance, a signal at least ten times the background noise. It describes the method, not the sample. Limits are not findings.
<LOQ — A censored value: the analyte, if present, sat below the amount the method can quantify. It is not zero and it is not a quantity. Reading a censored row.
ppm — Parts per million by weight. One ppm is one microgram per gram, so a figure in ppm multiplied by the grams in a serving gives micrograms per serving. Units on a certificate.
CFU — Colony-forming unit, the count used on microbiology rows: one viable cell or cluster that grows into a colony. A reading of under 20 CFU per gram is the method’s floor, not a count of zero. What a microbiology page covers.
ICP-MS — Inductively coupled plasma mass spectrometry, the instrument method that counts elements such as lead and magnesium. It measures the element and cannot say which compound carried it. Metals rows, read properly.
HPLC — High-performance liquid chromatography, a method that separates a mixture and measures each component. It is the usual method behind a creatine purity figure. Methods on a certificate.
Customer of record — The company that commissioned and paid for a certificate, printed on its face. If it is not the brand handing the document over, that brand did not commission it. Whose paperwork it is.
Raw material — An ingredient before it becomes a product: a sack of powder rather than a filled container. A certificate on raw material describes the ingredient, not anything a person can buy. Whose sample it was.
NT — The abbreviation certificates print for an analyte that was not run. An NT row and a missing row say the same thing: no finding exists for that axis. Reading what was not run.
Proposition 65 — California’s law requiring a warning when exposure to a listed chemical exceeds a safe-harbour level. For lead, the level for reproductive toxicity is 0.5 micrograms a day and the cancer level is 15. Per serving against per day.
What does LOQ mean on a certificate of analysis?
LOQ is the limit of quantification: the lowest amount a laboratory method can measure with suitable precision and accuracy. FDA’s 2024 guidance gives one accepted way of setting it, a signal at least ten times the background noise. It describes the method, not the sample. A reading of <LOQ means the analyte, if present, sat below that floor: not zero, and not a quantity.
How do you convert ppm on a certificate into micrograms per serving?
Multiply the ppm figure by the weight of a serving in grams. One part per million is one microgram per gram, so 0.5 ppm of lead in a 10 g serving is 5 micrograms. Two cautions: the figure describes the sample the laboratory received, which may not be the product you take, and a per-day limit compares only with everything you take in a day.
Research terms
Randomised controlled trial — A study that assigns participants to the supplement or a comparison by chance, so that on average the groups differ only by what they took. GRADE starts it at high certainty. Study designs, ranked.
Placebo — An inactive look-alike given to the comparison group, so that participants cannot tell which they received. Why the comparison matters.
Double-blind — Neither the participants nor the researchers measuring them know who received what until the analysis, so expectation cannot steer either side. Design questions to ask.
Crossover trial — Each participant takes every arm in turn, separated by a washout, and serves as their own comparison. It needs fewer participants than a parallel design to detect the same effect, which suits small supplement studies. What eight participants can show.
Systematic review — A review that searches for every study on a question by a stated method, assesses each for bias, and reports how it chose them. It may or may not pool the numbers. Reviews against meta-analyses.
Meta-analysis — A statistical pooling of several studies’ findings, usually those a systematic review found, into one estimate with a confidence interval. It adds precision and inherits every weakness of what it pools. How to read one.
Effect size — How large a difference is, as opposed to whether it is likely to be real. It is often expressed in standard deviations, so that studies using different measurements can be compared. What 0.19 means.
SMD — The pooled effect size meta-analyses print: the difference between groups divided by the spread of the measurements. An SMD of 0.19 is about a fifth of a standard deviation. Why it travels with its certainty.
Confidence interval — The range of effects compatible with the data at a stated level, usually 95%. A wide interval means the study could not pin the effect down, whatever its headline figure. Reading precision.
p-value — The probability of a difference at least this large if there were truly no effect. It says nothing about how large or important the effect is, and 0.05 is a convention, not a verdict. Size against significance.
GRADE — A system for rating confidence in a body of evidence as high, moderate, low or very low. Randomised trials start high and lose levels for study limitations, inconsistency, indirectness, imprecision and publication bias. What each level means.
Surrogate marker — A measurement standing in for the outcome that matters, such as a blood marker of collagen synthesis in place of a tendon. A change in the marker is not a change in the tissue. Markers against outcomes.
Funding statement — The declaration, usually at the end of a paper, of who paid for the work, alongside the authors’ ties to companies with an interest in the finding. Donated product counts. How to check who paid.
Narrative review — A review that summarises a literature without a systematic search or a formal assessment of bias. It is useful for ideas and weak as evidence, however often it is cited. One that frames a whole category.
Rules and intake standards
Structure/function claim — A label statement describing how a nutrient or dietary ingredient affects the body’s normal structure or function. 21 CFR 101.93 allows one only with substantiation, a disclaimer and notice to FDA within 30 days of first marketing. What a label cannot claim.
Disclaimer — The sentence 21 CFR 101.93 requires with every structure/function claim, beginning “This statement has not been evaluated by the Food and Drug Administration”, set in bold type at least one-sixteenth of an inch tall. Where the asterisk leads.
Recommended Dietary Allowance (RDA) — The average daily intake that meets the requirement of nearly all healthy people, 97 to 98%, in an age and sex group. For magnesium in men 31 and older it is 420 mg. Magnesium by age.
Adequate Intake — The intake set instead of an RDA when the evidence cannot support calculating an average requirement; at that level, nutritional adequacy is assumed. How intake targets are set.
Estimated Average Requirement (EAR) — The intake estimated to meet the requirement of half the healthy people in a group, used to assess the intakes of populations rather than to advise individuals. Requirement against allowance.
Tolerable Upper Intake Level (UL) — The highest daily intake likely to pose no risk of adverse effects for almost everyone. For magnesium it is 350 mg a day in adults, counting supplements and medications only, not food. The 350 mg line.
Dietary Reference Intakes (DRI) — The family of reference values — RDA, Adequate Intake, EAR and UL — set by the Institute of Medicine of the National Academies; magnesium’s were published in 1997. Magnesium’s values in full.
Expiration date — The date a manufacturer prints as the end of a product’s shelf life. On a supplement it is the manufacturer’s own statement, and its basis is worth asking for. What a printed date means.
What is a structure/function claim on a supplement label?
It is a statement that a nutrient or ingredient affects the body’s normal structure or function — the kind of sentence that carries an asterisk. Under 21 CFR 101.93 a supplement may make one only if the company holds substantiation, notifies FDA within 30 days of first marketing and prints the disclaimer beside it. A claim about a named medical condition is not available to a supplement at all.
What is the difference between the RDA, Adequate Intake and the upper limit?
The RDA is the daily intake that meets the requirement of 97 to 98% of healthy people; an Adequate Intake is set instead when the evidence cannot support an RDA; and the Tolerable Upper Intake Level is the highest daily intake unlikely to cause adverse effects. For magnesium in men 31 and older: an RDA of 420 mg from all sources, and a ceiling of 350 mg from supplements alone.
What a definition does not show
A definition explains a word; it does not vouch for any product that prints it. Chelated, micronised and bisglycinate describe chemistry, and none of them is a measurement of what a capsule holds — only a certificate’s measured row is, and only for the sample the laboratory received. The regulatory definitions are quoted as they stood on 17 October 2026, and rules change. The research terms describe how to weigh a study, not what any study found: the findings themselves, with their limits, are on the evidence tables for creatine, collagen and magnesium, and the method for reading them is on how to read supplement research.
Where TARE’s own labels use these words, they are used as defined. Night Work’s panel declares 275 mg of elemental magnesium from 2,500 mg of magnesium glycinate; Base Work’s certificate covers a raw-material lot and records its serving size as N/A; and Under Load’s declared serving is 10 g, two 5 g scoops, which is a serving and not our 15 g protocol. Every certificate we hold, and what each does and does not cover, is transcribed on Testing & Certification.
Sources
- 21 CFR 101.36. Nutrition labeling of dietary supplements. Electronic Code of Federal Regulations (accessed 17 October 2026). ecfr.gov
- 21 CFR 101.93. Certain types of statements for dietary supplements. Electronic Code of Federal Regulations (accessed 17 October 2026). ecfr.gov
- 21 CFR 111.3. Definitions that apply to dietary supplement manufacturing. Electronic Code of Federal Regulations (accessed 17 October 2026). ecfr.gov
- US Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels (content current as of 5 March 2024). fda.gov
- US Food and Drug Administration. Q2(R2) Validation of Analytical Procedures: Guidance for Industry (March 2024). fda.gov
- California Office of Environmental Health Hazard Assessment. Proposition 65: Lead, chemical listing and safe harbor levels. oehha.ca.gov
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals (updated 6 January 2026). NIH Office of Dietary Supplements
- Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academies Press; 1997. Summary. nationalacademies.org
- Leon-Lopez A, Morales-Penaloza A, Martinez-Juarez VM, et al. Molecules 2019;24(22):4031. doi:10.3390/molecules24224031
- Institute of Medicine. Finding What Works in Health Care: Standards for Systematic Reviews. Washington, DC: National Academies Press; 2011. Chapter 4. nationalacademies.org