Clinical Nutrition

Lesson 6: Vitamin A Deficiency

Dark adaptation threshold

Night blindness caused by a reduced concentration of rhodopsin in the rod is often used to determine vitamin A deficiency.

Biochemical indicators such as serum retinal and breast milk retinal are also used to assess vitamin A deficiency. A serum retinol concentration of <10 µg/dl is considered deficient, <20 µg/dl is low and ≥30µg/dl is accepted as adequate vitamin A status. Levels below 20µg/dl indicate the presence of subclinical vitamin A deficiency.

The concentration of vitamin A in breast milk serves as an indicator of the vitamin A status of the breast fed infant. A cut off value of 10µg/litre indicates that the infant is at a risk of vitamin A deficiency.