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Author: Brian Wu PhD. MD Candidate, Keck School of Medicine, Los Angeles, USA. Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, October 2015.
Vitamin A is a fat soluble retinoid. It also called retinol. Vitamin A is needed for immunity, visual and dermatological health as well as cell communication and growth. In excessive amounts, however, it can accumulate in the liver and cause a wide array of symptoms. Toxicity is classified as either acute or chronic.
Vitamin A toxicity is also known as hypervitaminosis A.
The most common cause of acute vitamin A toxicity is the ingestion (generally accidental) of over 300,000 IU of vitamin A.
The most common cause of chronic vitamin A toxicity is the regular ingestion of over 100,000 IU daily, which is sometimes prescribed for dermatological conditions such as acne.
Signs and symptoms of acute vitamin A toxicity can include:
Signs and symptoms of chronic vitamin A toxicity can include:
In children, signs and symptoms of vitamin A toxicity are:
It is also important to note that vitamin A is highly teratogenic if taken during pregnancy (especially in the first 8 weeks) if intake exceeds 10,000 IU daily. Birth defects can also be caused by isotretinoin or other oral retinoids, if taken while pregnant.
Excessive intake of Vitamin A during pregnancy has been associated with the following birth defects, collectively known as retinoic acid syndrome:
Diagnosis of vitamin A toxicity is based on signs and symptoms, patient history, lifestyle habits and use of supplements. There is sometimes a poor correspondence between toxicity and serum retinol levels. However, serum levels can sometimes be between 1,000 and 20,000 (with a normal range being 200 to 800 µg/L). The blood sample must be protected from light.
Vitamin a toxicity is treated by stopping the use of vitamin A supplements. Generally, signs and symptoms will resolve on their own with 1–4 weeks, depending on their severity. Birth defects caused by vitamin A toxicity during pregnancy are irreversible.
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