Frank vitamin A deficiency is rare in the United States but common in many low- and middle-income countries; in 2013 about 29% of children aged 6 months to 5 years in those countries were deficient. It is one of the top causes of preventable blindness in children, and it makes infections such as measles and diarrhea more severe and more often fatal.
Common symptoms
Night blindness: trouble seeing in low light or darkness, usually the first sign
Dryness and damage of the eye surface and cornea (xerophthalmia), which can lead to permanent blindness
Bitot's spots on the whites of the eyes
More severe infections, especially measles and diarrhea
Anemia
Abnormal lung development and respiratory illness with long-term deficiency
At-risk groups
Premature infants, who are born with low liver stores
Infants, children, and pregnant and breastfeeding women in low- and middle-income countries
People with cystic fibrosis, because of poor fat absorption
People with Crohn's disease, ulcerative colitis or newly diagnosed celiac disease
When to see a doctorDifficulty seeing at night or in dim light, especially if it is getting worse, should be checked promptly, particularly in pregnancy or in anyone with a condition that affects fat absorption. Do not start high-dose vitamin A (more than 3,000 mcg or 10,000 IU a day) without medical advice: it builds up in the liver and excess in pregnancy can cause birth defects.