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Vitamin A
minimum sample volume required ~ 5ml
Test Code: VIA
Tube type: SST
Other acceptable tube types
Lithium heparin (pale green)
Special instructions
None
Reference ranges
<4 years: 0.5-1.6
4-18 years: 0.8-2.2
Adult Male: 1.1-3.4
Adult Female: 0.8-3.0
Sent away
to Bristol Royal Infirmary
Units
µmol/L
Turnaround Time
14
days
Department: Biochemistry
Clinical Application
Retinol is the primary form of vitamin A in animals. Vitamin A is an essential nutrient required for healthy vision, skin growth and integrity, bone formation, immune function, and embryonic development. It is required to produce photoreceptors in the eyes and to maintain the lining of the surface of the eyes and other mucous membranes. Deficiencies in vitamin A can impair night vision, cause eye damage, and in severe cases lead to blindness.
In the UK, most individuals are well nourished. Vitamin A (retinol) deficiency is confined to those individuals with malabsorption due to small intestinal disease, pancreatic insufficiency, e.g. cystic fibrosis or alcoholic and biliary cirrhosis, short gut syndrome.
Vitamin A levels only decrease in severe deficiency when hepatic stores have fallen.
Vitamin A levels can decrease in infection due to the acute phase response (consider checking CRP).
Vitamin A toxicity is rare and usually associated with excess supplements.
If possible, vitamin supplements should be stopped 2 days prior to sampling as the vitamins can appear in the blood up to 32 hours post ingestion.
Webpage updated: December 2024
