Vitamin A supplementation in adults
See Clinical aspects of fat-soluble vitamins for the physiological function of vitamin A, and the effects of and risk factors for vitamin A deficiency. Deficiency is rare in developed countries but common in developing countries.
Vitamin A is available in 2 main forms, provitamin A (eg beta-carotene, alpha-carotene, beta-cryptoxanthin) and preformed vitamin A (eg retinol, retinal, retinoic acid, retinyl esters). Most supplements contain preformed vitamin A; however, some supplements may contain a mixture of provitamin A and preformed vitamin ANational Health and Medical Research Council (NHMRC), Updated 22 September 2017.
Vitamin A blood concentration may be decreased in acute or chronic inflammatory conditions, or infections—consider if inflammation or infection is present before starting supplementationMcMillan, 2019.
To treat vitamin A deficiency in adults, use:
Daily intake of vitamin A for adults, particularly if pregnant or breastfeeding, should not exceed 10 000 international units because there is a risk of birth defects and toxicityTherapeutic Research Center (trc), 2021.
Higher doses or intramuscular administration of vitamin A2 may be required if oral absorption is severely impaired.
Excess retinol can cause nausea, alopecia, blurred vision, orange skin discolouration, ataxia and hepatotoxicity, and can be teratogenic. Excess beta-carotene turns skin and eyes yellow or orangeTherapeutic Research Center (trc), 2021.