Nutrient form guide
Vitamin and mineral forms: how to read label names
For any vitamin or mineral product, write down the nutrient name, compound form, amount per serving, and percent Daily Value before reading the front-label claim.
The quick read
- The NIH Office of Dietary Supplements documents individual vitamins and minerals at the compound level, including what form differences can mean. NIH ODS magnesium fact sheet NIH ODS vitamin D fact sheet NIH ODS vitamin A fact sheet NIH ODS iron fact sheet
- FDA label formats show percent Daily Value, which is a reference level rather than a clinical target for any individual. FDA changes to the Nutrition Facts label FDA dietary supplement labeling guide
- Auditable mineral labels state the compound form and keep allergen and interaction caveats visible. FDA dietary supplement labeling guide FDA 101 dietary supplements
- Claim language should attach to the exact compound and amount rather than the broad nutrient name. FDA supplement claim substantiation guidance FTC health products compliance guidance
What the evidence says
Bottom line
Magnesium supplements use different compounds. NIH ODS lists citrate among the forms more easily absorbed by the body, so the form and elemental amount should be read together. NIH ODS magnesium fact sheet FDA dietary supplement labeling guide
Start with those four details, then see how much claim the label has stacked on top of them. FDA changes to the Nutrition Facts label FDA dietary supplement labeling guide
Compound names are not trivia
The exact form can affect properties such as absorption, so the compound name belongs in the comparison. NIH ODS magnesium fact sheet NIH ODS iron fact sheet NIH ODS vitamin D fact sheet
Given a choice, take the label that is precise about form and vague about benefits over the one making a precise claim with no form named.
Where these labels lose clarity
Readability improves as soon as compound names are spelled out and no broad claim appears without its dose context. FDA dietary supplement labeling guide FDA supplement claim substantiation guidance
Mood, energy, or immunity marketing cannot compensate for a form and amount that are difficult to follow. FTC health products compliance guidance FDA 101 dietary supplements
What to check on the label
Compound name
Look for both the named form and the elemental nutrient amount.
Dose context
Pair the compound name with its milligram amount and serving context.
Fat-soluble caution
Be careful with fat-soluble nutrient claims that skip dose and context.
Sources
- NIH ODS magnesium fact sheet: https://ods.od.nih.gov/factsheets/Magnesium-Consumer/
- NIH ODS vitamin D fact sheet: https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
- NIH ODS vitamin A fact sheet: https://ods.od.nih.gov/factsheets/VitaminA-Consumer/
- NIH ODS iron fact sheet: https://ods.od.nih.gov/factsheets/Iron-Consumer/
- FDA dietary supplement labeling guide: https://www.fda.gov/food/dietary-supplements-guidance-documents-regulatory-information/dietary-supplement-labeling-guide-chapter-iv-nutrition-labeling
- FDA changes to the Nutrition Facts label: https://www.fda.gov/food/nutrition-food-labeling-and-critical-foods/changes-nutrition-facts-label
- FDA 101 dietary supplements: https://www.fda.gov/consumers/consumer-updates/fda-101-dietary-supplements
- FDA supplement claim substantiation guidance: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-substantiation-dietary-supplement-claims-made-under-section-403r-6-federal-food
- FTC health products compliance guidance: https://www.ftc.gov/business-guidance/resources/health-products-compliance-guidance
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Read the editorial policy and scoring methodology. Sources favor primary canon, regulators, product labels, and peer-reviewed research; reputable secondary reporting is identified when used.
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Sources: 9 entries, all primary canon, last reviewed 2026-09-01.
For research and educational purposes only. Not medical advice.