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Glossary

What are fat-soluble vitamins?

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

Fat-soluble vitamins are the vitamins that dissolve in fat rather than water: vitamins A, D, E and K. They are absorbed along with dietary fat, and the body can store them, so excess can build up over time. Vitamins A, D and E have upper limits for adults; vitamin K has none.1,2,3,4

Key facts

  • Vitamin K, like dietary fats and the other fat-soluble vitamins, is packed into micelles with the help of bile and pancreatic enzymes before the small intestine absorbs it.4
  • Because vitamin A is fat soluble, the body stores excess amounts, mainly in the liver, and levels can accumulate.1
  • Vitamin D is best absorbed when taken with a meal or snack that includes some fat.5
  • No upper limit is set for vitamin K because of its low potential for toxicity.4

The four fat-soluble vitamins

Fat-soluble vitamins at a glance (adults)1,2,3,4
VitaminUpper limitNote
A3,000 mcg a day of preformed vitamin AStored mainly in the liver
D100 mcg (4,000 IU) a dayAbsorption depends on dietary fat
E1,000 mg a day of supplemental alpha-tocopherolThe gut needs fat to absorb it
KNone setRapidly broken down; little circulates in blood

Why fat in the meal matters

These vitamins travel with fat through digestion. In the small intestine, bile and pancreatic enzymes pack them into tiny droplets called micelles along with dietary fat, and only then are they absorbed. Anything that lowers fat absorption lowers their absorption too.2,3,4

That is the reasoning behind NIH's advice to take vitamin D with a meal or snack that contains some fat.5

Storage, upper limits and medicines

Because the body holds on to fat-soluble vitamins, high doses taken for a long time can build up. Stay within the upper limits unless a doctor advises otherwise, and count every source: multivitamins, single supplements and fortified foods.1

Some medicines lower absorption of fat-soluble vitamins, including orlistat, a weight-loss medicine, and bile acid sequestrants such as cholestyramine. Ask your doctor or pharmacist if you take one.1,4

Questions people ask

Should I take fat-soluble vitamins with food?

Taking them with a meal that contains some fat fits how they are absorbed. NIH's vitamin D consumer sheet says vitamin D is best absorbed this way.4,5

Are fat-soluble vitamins stored in the body?

Yes. Vitamin A is stored mainly in the liver, and vitamin D can be released from fat stores. Vitamin K is the exception among them: it is broken down quickly, and the body keeps relatively little.1,2,4

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Sources

  1. Office of Dietary Supplements, National Institutes of Health. Vitamin A and Carotenoids: Fact Sheet for Health Professionals. Updated March 10, 2025. Opened 2026-10-07.
  2. Office of Dietary Supplements, National Institutes of Health. Vitamin D: Fact Sheet for Health Professionals. Updated June 27, 2025. Opened 2026-10-07.
  3. Office of Dietary Supplements, National Institutes of Health. Vitamin E: Fact Sheet for Health Professionals. Updated March 26, 2021. Opened 2026-10-07.
  4. Office of Dietary Supplements, National Institutes of Health. Vitamin K: Fact Sheet for Health Professionals. Updated March 29, 2021. Opened 2026-10-07.
  5. Office of Dietary Supplements, National Institutes of Health. Vitamin D: Fact Sheet for Consumers. Updated November 8, 2022. Opened 2026-10-07.

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