Background

Vitamin A is a fat-soluble vitamin. Its different forms are often called "retinoids." They include retinol, retinal, retinoic acid, and retinyl ester.

Vitamin A is needed for the proper growth and functioning of many parts of the body, including the eyes, skin, and immune system. It can be found in many foods, including fruits, vegetables, and fish. Carotenoids are a group of chemicals found in plants. Some can be converted to vitamin A in the body.

People most commonly use vitamin A for treating vitamin A deficiency. It is also used for aging skin, acne, HIV/AIDS, cataracts, child development, infections, and many other conditions.

Safety Safety definitions

When taken by mouth: Vitamin A is likely safe when taken in amounts less than 10,000 units (3,000 mcg) daily. Vitamin A is available in two forms: pre-formed vitamin A (retinol or retinyl ester) and provitamin A (carotenoids). The maximum daily dose relates to only pre-formed vitamin A.

Pre-formed vitamin A is possibly unsafe when taken in doses greater than 10,000 units (3,000 mcg) daily. Higher doses might increase the risk of side effects. Long-term use of large amounts might cause serious side effects including mental changes.

When applied to the skin: Vitamin A is possibly safe when used short-term. Retinol 0.5% serum has been used daily for up to 12 weeks without serious side effects.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Vitamin A is likely safe when taken in recommended amounts of less than 10,000 units (3,000 mcg) of pre-formed vitamin A daily. Larger amounts are possibly unsafe and can cause birth defects. Monitor vitamin A intake from all sources during the first three months of pregnancy. Forms of vitamin A are found in several foods including animal liver, some fortified breakfast cereals, and dietary supplements.

Children: Vitamin A is likely safe when taken in the recommended amounts. The maximum amounts of vitamin A that are safe for children are based on age. Vitamin A is possibly unsafe for children when taken by mouth in high doses. Taking high doses can cause side effects, including irritability, sleepiness, diarrhea, and other problems.

Excessive use of alcohol: Drinking alcohol might increase vitamin A's potentially harmful effects on the liver.

Disorders in which the body does not absorb fat properly: People with conditions that affect fat absorption are not able to absorb vitamin A properly. These conditions include celiac disease, short gut syndrome, jaundice, cystic fibrosis, pancreatic disease, and cirrhosis of the liver. If you have one of these conditions, take water-soluble forms of vitamin A, called carotenoids, instead.

Iron deficiency: Iron deficiency might affect the body's ability to use vitamin A.

Liver disease: Too much vitamin A might make liver disease worse. Do not take vitamin A supplements if you have liver disease.

Malnutrition: In people with severe protein malnutrition, taking vitamin A supplements might result in having too much vitamin A in the body.

Zinc deficiency: Zinc deficiency might cause symptoms of vitamin A deficiency. Taking a combination of vitamin A and zinc supplements might be necessary to improve this condition.

Effectiveness

Dosing & administration

Vitamin A is an important nutrient. It is found in many foods, including fruits, vegetables, eggs, whole milk, meat, and fish. The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). The RDA is 900 mcg daily for males and 700 mcg daily for females. While pregnant, the RDA is 770 mcg daily. While breast-feeding, the RDA is 1300 mcg daily. In children, the RDA depends on age.

In supplements, vitamin A is available in two forms: pre-formed vitamin A (retinol or retinyl ester) and provitamin A (carotenoids). For products that contain both, only count the amount of pre-formed vitamin A to determine what is safe. Vitamin A is also available in many topical products, including creams, serums, and lotions. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.

Interactions with pharmaceuticals

Antibiotics (Tetracycline antibiotics)

Interaction Rating=Moderate Be cautious with this combination.

Taking very large amounts of vitamin A along with tetracyclines can increase the chance of a serious side effect called intracranial hypertension. But taking normal doses of vitamin A along with tetracyclines does not seem to cause this problem. Do not take large amounts of vitamin A if you are taking antibiotics.

Medications for skin conditions (Retinoids)

Interaction Rating=Major Do not take this combination.

Some medications for skin conditions are made from vitamin A. Taking vitamin A and these medications together could cause toxic effects.

Medications that can harm the liver (Hepatotoxic drugs)

Interaction Rating=Moderate Be cautious with this combination.

Taking large amounts of vitamin A might harm the liver. Some medications can also harm the liver. Taking high doses of vitamin A along with a medication that can harm the liver might increase the risk of liver damage.

Warfarin (Coumadin)

Interaction Rating=Moderate Be cautious with this combination.

Warfarin is used to slow blood clotting. Large amounts of vitamin A can also slow blood clotting. Taking vitamin A along with warfarin can increase the chances of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your warfarin might need to be changed.

Interactions with herbs & supplements

Iron: Red blood cells need iron to make hemoglobin, the chemical that carries oxygen through the body. Taking vitamin A seems to improve hemoglobin levels in people who have low levels of iron and vitamin A.

Interactions with foods

There are no known interactions with foods.