Recommended Dietary Allowance, Adequate Intake, and Tolerable Upper Intake Level: Plain‑English Guide (Adults 19–50)

Quick definitions

• Recommended Dietary Allowance (RDA): daily average that meets the needs of ~97–98% of healthy people.
• Adequate Intake (AI): best estimate when an allowance cannot be set.
• Tolerable Upper Intake Level (UL): highest daily intake likely to pose no risk for most people.
• Dietary Reference Intakes are set by the U.S. National Academies (NASEM).
• Use these for planning and checking diets and supplements.

How to use these numbers

• The U.S. National Academies (NASEM) say: use the RDA or AI as your daily goal. This helps prevent nutrient gaps.
• Try to hit the goal on average over several days, not every single day.
• Do not go over the Upper Level (UL) from food + supplements unless your doctor tells you to.
• Needs change by age, sex, and life stage. These values are for adults 19–50.
• Check the units (mg, µg, g, L). Some ULs apply only to supplement forms.
• This page is for information only, not medical advice.
• Amounts are per day unless noted.

Adults 19–50: Men

Vitamins

• Vitamin A
  • Recommended Dietary Allowance: 900 µg RAE
  • Tolerable Upper Intake Level: 3000 µg (preformed retinol)
• Vitamin C
  • Recommended Dietary Allowance: 90 mg
  • Tolerable Upper Intake Level: 2000 mg
• Vitamin D
  • Recommended Dietary Allowance: 15 µg (minimal sun)
  • Tolerable Upper Intake Level: 100 µg
• Vitamin E (alpha‑tocopherol)
  • Recommended Dietary Allowance: 15 mg
  • Tolerable Upper Intake Level: 1000 mg (α‑tocopherol, supplemental)
• Vitamin K
  • Adequate Intake: 120 µg
  • Tolerable Upper Intake Level: not established
• Thiamin (B1)
  • Recommended Dietary Allowance: 1.2 mg
  • Tolerable Upper Intake Level: not established
• Riboflavin (B2)
  • Recommended Dietary Allowance: 1.3 mg
  • Tolerable Upper Intake Level: not established
• Niacin
  • Recommended Dietary Allowance: 16 mg NE
  • Tolerable Upper Intake Level: 35 mg (synthetic)
• Vitamin B6
  • Recommended Dietary Allowance: 1.3 mg
  • Tolerable Upper Intake Level: 100 mg
• Folate
  • Recommended Dietary Allowance: 400 µg DFE
  • Tolerable Upper Intake Level: 1000 µg (synthetic folic acid)
• Vitamin B12
  • Recommended Dietary Allowance: 2.4 µg
  • Tolerable Upper Intake Level: not established
• Pantothenic acid
  • Adequate Intake: 5 mg
  • Tolerable Upper Intake Level: not established
• Biotin
  • Adequate Intake: 30 µg
  • Tolerable Upper Intake Level: not established
• Choline
  • Adequate Intake: 550 mg
  • Tolerable Upper Intake Level: 3.5 g

Minerals

• Calcium
  • Recommended Dietary Allowance: 1000 mg
  • Tolerable Upper Intake Level: 2500 mg
• Chromium
  • Adequate Intake: 35 µg
  • Tolerable Upper Intake Level: not established
• Copper
  • Recommended Dietary Allowance: 900 µg
  • Tolerable Upper Intake Level: 10000 µg
• Fluoride
  • Adequate Intake: 4 mg
  • Tolerable Upper Intake Level: 10 mg
• Iodine
  • Recommended Dietary Allowance: 150 µg
  • Tolerable Upper Intake Level: 1100 µg
• Iron
  • Recommended Dietary Allowance: 8 mg
  • Tolerable Upper Intake Level: 45 mg
• Manganese
  • Adequate Intake: 2.3 mg
  • Tolerable Upper Intake Level: 11 mg
• Molybdenum
  • Recommended Dietary Allowance: 45 µg
  • Tolerable Upper Intake Level: 2000 µg
• Phosphorus
  • Recommended Dietary Allowance: 700 mg
  • Tolerable Upper Intake Level: 4 g
• Selenium
  • Recommended Dietary Allowance: 55 µg
  • Tolerable Upper Intake Level: 400 µg
• Zinc
  • Recommended Dietary Allowance: 11 mg
  • Tolerable Upper Intake Level: 40 mg
• Potassium
  • Adequate Intake: 3400 mg
  • Tolerable Upper Intake Level: not established
• Sodium
  • Adequate Intake: 1500 mg
  • Tolerable Upper Intake Level: not established
• Chloride
  • Adequate Intake: 2.3 g
  • Tolerable Upper Intake Level: 3.6 g

Water and macronutrients

• Total water (all beverages + foods)
  • Adequate Intake: 3.7 L
  • Tolerable Upper Intake Level: not established
• Carbohydrate
  • Recommended Dietary Allowance: 130 g
  • Tolerable Upper Intake Level: not established
• Total fiber
  • Adequate Intake: 38 g
  • Tolerable Upper Intake Level: not established
• Linoleic acid (omega‑6)
  • Adequate Intake: 17 g
  • Tolerable Upper Intake Level: not established
• Alpha‑linolenic acid (omega‑3)
  • Adequate Intake: 1.6 g
  • Tolerable Upper Intake Level: not established
• Protein
  • Recommended Dietary Allowance: 0.8 g/kg
  • Tolerable Upper Intake Level: not established

Adults 19–50: Women

Vitamins

• Vitamin A
  • Recommended Dietary Allowance: 700 µg RAE
  • Tolerable Upper Intake Level: 3000 µg (preformed retinol)
• Vitamin C
  • Recommended Dietary Allowance: 75 mg
  • Tolerable Upper Intake Level: 2000 mg
• Vitamin D
  • Recommended Dietary Allowance: 15 µg (minimal sun)
  • Tolerable Upper Intake Level: 100 µg
• Vitamin E (alpha‑tocopherol)
  • Recommended Dietary Allowance: 15 mg
  • Tolerable Upper Intake Level: 1000 mg (α‑tocopherol, supplemental)
• Vitamin K
  • Adequate Intake: 90 µg
  • Tolerable Upper Intake Level: not established
• Thiamin (B1)
  • Recommended Dietary Allowance: 1.1 mg
  • Tolerable Upper Intake Level: not established
• Riboflavin (B2)
  • Recommended Dietary Allowance: 1.1 mg
  • Tolerable Upper Intake Level: not established
• Niacin
  • Recommended Dietary Allowance: 14 mg NE
  • Tolerable Upper Intake Level: 35 mg (synthetic)
• Vitamin B6
  • Recommended Dietary Allowance: 1.3 mg
  • Tolerable Upper Intake Level: 100 mg
• Folate
  • Recommended Dietary Allowance: 400 µg DFE
  • Tolerable Upper Intake Level: 1000 µg (synthetic folic acid)
• Vitamin B12
  • Recommended Dietary Allowance: 2.4 µg
  • Tolerable Upper Intake Level: not established
• Pantothenic acid
  • Adequate Intake: 5 mg
  • Tolerable Upper Intake Level: not established
• Biotin
  • Adequate Intake: 30 µg
  • Tolerable Upper Intake Level: not established
• Choline
  • Adequate Intake: 425 mg
  • Tolerable Upper Intake Level: 3.5 g

Minerals

• Calcium
  • Recommended Dietary Allowance: 1000 mg
  • Tolerable Upper Intake Level: 2500 mg
• Chromium
  • Adequate Intake: 25 µg
  • Tolerable Upper Intake Level: not established
• Copper
  • Recommended Dietary Allowance: 900 µg
  • Tolerable Upper Intake Level: 10000 µg
• Fluoride
  • Adequate Intake: 3 mg
  • Tolerable Upper Intake Level: 10 mg
• Iodine
  • Recommended Dietary Allowance: 150 µg
  • Tolerable Upper Intake Level: 1100 µg
• Iron
  • Recommended Dietary Allowance: 18 mg
  • Tolerable Upper Intake Level: 45 mg
• Manganese
  • Adequate Intake: 1.8 mg
  • Tolerable Upper Intake Level: 11 mg
• Molybdenum
  • Recommended Dietary Allowance: 45 µg
  • Tolerable Upper Intake Level: 2000 µg
• Phosphorus
  • Recommended Dietary Allowance: 700 mg
  • Tolerable Upper Intake Level: 4 g
• Selenium
  • Recommended Dietary Allowance: 55 µg
  • Tolerable Upper Intake Level: 400 µg
• Zinc
  • Recommended Dietary Allowance: 8 mg
  • Tolerable Upper Intake Level: 40 mg
• Potassium
  • Adequate Intake: 2600 mg
  • Tolerable Upper Intake Level: not established
• Sodium
  • Adequate Intake: 1500 mg
  • Tolerable Upper Intake Level: not established
• Chloride
  • Adequate Intake: 2.3 g
  • Tolerable Upper Intake Level: 3.6 g

Water and macronutrients

• Total water (all beverages + foods)
  • Adequate Intake: 2.7 L
  • Tolerable Upper Intake Level: not established
• Carbohydrate
  • Recommended Dietary Allowance: 130 g
  • Tolerable Upper Intake Level: not established
• Total fiber
  • Adequate Intake: 25 g
  • Tolerable Upper Intake Level: not established
• Linoleic acid (omega‑6)
  • Adequate Intake: 12 g
  • Tolerable Upper Intake Level: not established
• Alpha‑linolenic acid (omega‑3)
  • Adequate Intake: 1.1 g
  • Tolerable Upper Intake Level: not established
• Protein
  • Recommended Dietary Allowance: 0.8 g/kg
  • Tolerable Upper Intake Level: not established

Notes on units and forms

• µg = microgram. mg = milligram. g = gram. L = liter.
• Vitamin A uses µg RAE (retinol activity equivalents).
• Folate uses µg DFE (dietary folate equivalents).
• Niacin uses mg NE (niacin equivalents).
• Some Tolerable Upper Intake Levels apply to supplemental forms only (e.g., vitamin E, folic acid).
• Vitamin D values assume minimal sun exposure.

Safety and context

• Going above the Tolerable Upper Intake Level can increase risk over time. Short spikes can still matter.
• Every body is different.
• People can react differently to the same dose.
• Sensitivity to each compound can vary a lot.
• Be cautious if you decide to use supplements.
• Adjust to your personal needs with care.
• Special groups (pregnancy, lactation, athletes, certain conditions) may need different targets.
• Talk to your clinician about supplements and high intakes.

References

1. National Academies of Sciences, Engineering, and Medicine (NASEM). Dietary Reference Intakes Summary Tables. 2019. Appendix J. NCBI Bookshelf.
2. NIH Office of Dietary Supplements (ODS). Nutrient Fact Sheets. General reference for units and terms.

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