Vitamin A is essential for good vision, skin growth and quality, bone formation and fetal growth. Vitamin A must come from vitamin A supplements or precursors in our diet (retinol from meat or carotene from fruit and vegetables). Some dietary deficiencies or intestinal absorption problems can lead to harmful vitamin A deficiencies. Test results are expressed in micromoles of vitamin A per litre of blood (umol/L).
A normal level of vitamin A in the blood indicates that the individual has enough vitamin A, but does not indicate whether he has enough vitamin A in reserve during certain conditions (illness, pregnancy). Lower-than-normal levels indicate that the reserves are exhausted and that the individual has a vitamin A deficiency. A higher-than-normal level indicates that the body’s storage capacity has been exceeded and that the individual is at risk of vitamin A toxicity (headaches, nausea, vomiting, double vision, fatigue, weakness, etc.). Excessive dietary beta-carotene intake may cause a yellow-orange skin coloration, but does not cause vitamin A toxicity.