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Medical Author: Betty Kovacs, MS, RD
Medical Editor: Melissa Conrad Stöppler, MD

What are vitamins?

Vitamins are an essential part of our diet. Without an adequate amount of vitamins, a deficiency will occur. Vitamins are naturally found in the foods that we consume and are also found in supplements. A well-balanced diet is often enough to meet the vitamin needs of healthy individuals. When a supplementation is needed, it is important to know how much you need to take and the best way to take it.

Vitamin A

Vitamin A has many important functions in your body. It helps regulate your immune system, helps form and maintain healthy teeth, skin, and tissue, it produces the pigments in the retina of the eye, and promotes good vision. A deficiency in this vitamin can lead to problems with any of these. The vitamin A found in plants serves different functions than the vitamin A found in animals. The animal sources of vitamin A are liver, whole milk, and fortified foods, and the plant sources include colorful fruits and vegetables like carrots, spinach, kale, and cantaloupe.

The recommended dietary allowances (RDA) for vitamin A are listed as international units (IU) of retinol activity equivalents (RAE). This is done to account for the different actions of both forms of vitamin A.

The following is the RDA for vitamin A:

Age Males Females Pregnancy Lactation
1-3 years 1,000 IU 1,000 IU N/A N/A
4-8 years 1,320 IU 1,320 IU N/A N/A
9-13 years 2,000 IU 2,000 IU N/A N/A
14-18 years 3,000 IU 2,310 IU 2,500 IU 4,000 IU
19+ years 3,000 IU 2,310 IU 2,565 IU 4,300 IU

Going above the RDA for vitamin A can initially cause nausea, vomiting, irritability, drowsiness, altered mental status, anorexia, abdominal pain, blurred vision, muscle pain with weakness, and/or headache. Over time, this can lead to hypervitaminosis A or vitamin A toxicity. The harmful effects of this are birth defects, reduced bone density that may result in osteoporosis, central nervous system disorders, and liver abnormalities.

Medically Reviewed by a Doctor on 4/29/2016

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