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Glossary

What does elemental mean on a supplement label?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Elemental means the weight of the mineral itself, not of the whole compound it comes in. Calcium carbonate is 40% calcium by weight, so 1,000 mg of it supplies 400 mg of elemental calcium. On a Supplement Facts panel, the amount listed for a mineral is the elemental amount.1,2

Key facts

  • FDA rules require the weight of the nutrient, such as calcium, rather than the weight of its source, such as calcium carbonate.2,3
  • Forms differ a lot: calcium citrate is 21% calcium, and ferrous fumarate, sulfate and gluconate are 33%, 20% and 12% iron.1,4
  • Chromium picolinate is 12.4% chromium by weight.5
  • The source may be named in parentheses, as in Calcium (as calcium carbonate); if not, it must appear in the ingredient list.2
  • NIH notes that because the panel lists elemental amounts, you do not need to do the conversion yourself.1,4

Compound weight versus mineral weight

How much of each compound is the mineral itself1,4
CompoundShare that is the mineralMineral in 1,000 mg of the compound
Calcium carbonate40% calcium400 mg
Calcium citrate21% calcium210 mg
Ferrous fumarate33% iron330 mg
Ferrous sulfate20% iron200 mg
Ferrous gluconate12% iron120 mg

The panel already does this sum. A line reading Calcium 600 mg (as calcium carbonate) means 600 mg of calcium itself; the carbonate it is bound to adds more weight that the figure does not count.1,2

Which ingredients this applies to

The rule covers vitamins and minerals with Daily Values, and NIH fact sheets point it out for magnesium, zinc, potassium and chromium as well as calcium and iron. For ingredients without a Daily Value, such as an herbal extract, the weight listed is the weight of that ingredient, not of any one component in it.2,5,6,7,8

A compound's name is not always a guide to what it supplies. Potassium iodide is used in microgram amounts as a source of iodine, not of potassium.8

Why elemental amounts matter

Intake figures refer to the mineral, not the compound. NIH notes that the share of calcium absorbed is highest with doses of 500 mg or less of elemental calcium at one time, and that taking 25 mg or more of elemental iron at the same time as zinc can lower zinc absorption.1,7

Iron and children

Iron supplements in tablet or capsule form must carry an FDA warning that accidental overdose of iron products is a leading cause of fatal poisoning in children under 6. Since 1978, containers holding 250 mg or more of elemental iron must also be child resistant. Keep iron products out of children's reach.4,9

Questions people ask

Is elemental magnesium the same as magnesium?

Yes. Elemental magnesium is the magnesium itself. A Supplement Facts panel lists that amount, not the weight of the whole compound, such as magnesium oxide or citrate.6

Why does a 1,000 mg calcium carbonate tablet give only about 400 mg of calcium?

Calcium is about 40 percent of the weight of calcium carbonate; the rest is the carbonate. The Supplement Facts panel shows the calcium figure.1,2

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Sources

  1. NIH Office of Dietary Supplements. Calcium: Fact Sheet for Health Professionals. Updated June 22, 2026. Opened 2026-10-07.
  2. Code of Federal Regulations, Title 21, Section 101.36: Nutrition labeling of dietary supplements. Legal Information Institute, Cornell Law School (eCFR text). Opened 2026-10-07.
  3. U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling. April 2005. Opened 2026-10-07.
  4. NIH Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals. Updated September 4, 2025. Opened 2026-10-07.
  5. NIH Office of Dietary Supplements. Chromium: Fact Sheet for Health Professionals. Updated June 2, 2022. Opened 2026-10-07.
  6. NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. Updated January 6, 2026. Opened 2026-10-07.
  7. NIH Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals. Updated January 6, 2026. Opened 2026-10-07.
  8. NIH Office of Dietary Supplements. Potassium: Fact Sheet for Health Professionals. Updated June 2, 2022. Opened 2026-10-07.
  9. U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter VIII. Other Labeling Information. April 2005. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.