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Glossary

What is the RDA (Recommended Dietary Allowance)?

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

The Recommended Dietary Allowance (RDA) is the average daily intake that meets the nutrient needs of nearly all healthy people, 97 to 98 percent of them, in a given age and sex group. It is set by the Food and Nutrition Board of the National Academies, for example 90 mg of vitamin C a day for adult men.1

Key facts

  • The RDA is one of the Dietary Reference Intakes, alongside the Estimated Average Requirement, the Adequate Intake and the Tolerable Upper Intake Level.1
  • The Estimated Average Requirement meets the needs of half of healthy people; the RDA is pitched to cover nearly all.1
  • RDAs change with age, sex, pregnancy and lactation: magnesium is 400 mg for men aged 19 to 30 and 310 mg for women of the same age.2
  • Labels do not show RDAs. They show the FDA's Daily Value, one figure per nutrient that is usually one of the highest RDAs or Adequate Intakes.3
  • Some RDAs use special units that allow for different forms: mcg DFE for folate, mcg RAE for vitamin A and mg NE for niacin.4,5,6

How an RDA is used

NIH describes the RDA as the figure often used to plan nutritionally adequate diets for individuals. The Estimated Average Requirement is mostly used to assess and plan the intakes of groups. A healthy person whose usual intake meets the RDA for their age and sex is very likely getting enough.1

An RDA needs an Estimated Average Requirement behind it. When the data are too thin to set one, the board sets an Adequate Intake instead, as it has for biotin, vitamin K and potassium.7,8,9

Examples of adult RDAs

RDAs for adults aged 19 to 50, from NIH fact sheets1,2,4,5,6,10,11,12
NutrientMenWomen
Vitamin C90 mg75 mg
Vitamin D15 mcg (600 IU)15 mcg (600 IU)
Vitamin A900 mcg RAE700 mcg RAE
Folate400 mcg DFE400 mcg DFE
Niacin16 mg NE14 mg NE
Iron8 mg18 mg
Zinc11 mg8 mg
Magnesium, ages 31 to 50420 mg320 mg

Pregnancy raises several of these. The folate RDA goes from 400 mcg DFE to 600 mcg DFE, and iron from 18 mg to 27 mg.4,11

RDA versus the Daily Value on a label

For folate, niacin and vitamins A, D and E, the FDA based today's Daily Values on the highest adult RDA. That is why a label's 100% can be more than your own RDA. The iron Daily Value of 18 mg matches the RDA for women aged 19 to 50, while men of that age need 8 mg.11,13,14

Questions people ask

Is it fine to go over the RDA?

The RDA is a planning target, not a limit. The limit is the Tolerable Upper Intake Level, the most per day that is unlikely to cause adverse health effects, which is far higher than the RDA for many nutrients: 2,000 mg a day for vitamin C in adults, against an RDA of 90 mg for men.1

Do RDAs apply if I have a health condition?

RDAs are set for healthy people. Some reference values do not apply to people with certain conditions; NIH notes, for example, that the potassium intakes do not apply to people with kidney disease or taking medicines that impair potassium excretion. Ask your doctor which values apply to you.1,9

Who sets RDAs?

The Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine sets them as part of the Dietary Reference Intakes.1

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Sources

  1. NIH Office of Dietary Supplements. Vitamin C: Fact Sheet for Health Professionals. Updated July 31, 2025. Opened 2026-10-07.
  2. NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. Updated January 6, 2026. Opened 2026-10-07.
  3. NIH Office of Dietary Supplements. Multivitamin/mineral Supplements: Fact Sheet for Health Professionals. Updated July 17, 2024. Opened 2026-10-07.
  4. NIH Office of Dietary Supplements. Folate: Fact Sheet for Health Professionals. Updated November 30, 2022. Opened 2026-10-07.
  5. NIH Office of Dietary Supplements. Vitamin A and Carotenoids: Fact Sheet for Health Professionals. Updated March 10, 2025. Opened 2026-10-07.
  6. NIH Office of Dietary Supplements. Niacin: Fact Sheet for Health Professionals. Updated November 18, 2022. Opened 2026-10-07.
  7. NIH Office of Dietary Supplements. Biotin: Fact Sheet for Health Professionals. Updated January 10, 2022. Opened 2026-10-07.
  8. NIH Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. Updated March 29, 2021. Opened 2026-10-07.
  9. NIH Office of Dietary Supplements. Potassium: Fact Sheet for Health Professionals. Updated June 2, 2022. Opened 2026-10-07.
  10. NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. Updated June 27, 2025. Opened 2026-10-07.
  11. NIH Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals. Updated September 4, 2025. Opened 2026-10-07.
  12. NIH Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals. Updated January 6, 2026. Opened 2026-10-07.
  13. U.S. Food and Drug Administration. Converting Units of Measure for Folate, Niacin, and Vitamins A, D, and E on the Nutrition and Supplement Facts Labels: Guidance for Industry. August 2019. Opened 2026-10-07.
  14. U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. Content current as of March 5, 2024. Opened 2026-10-07.

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