Table 1.

Summary of common conditions associated with a clinical indication for measurement in blood i.e. serum / plasma.

	Deficiency	Excess
Vitamin A (retinol)	Cystic fibrosis	Acute ingestion
	Malabsorption*	Chronic ingestion
	Malnutrition
	Pancreatic insufficiency
Carotenoids (β-carotene)	Not generally measured	Differential diagnosis of change to colouring of skin – not toxic
Vitamin E (α-tocopherol)	Cystic fibrosis	Generally non-toxic
	Malabsorption*
	Malnutrition†
	Pancreatic insufficiency

^*Malabsorption of fat may be present in obstructive liver disease (e.g. biliary atresia), and in pancreatic dysfunction (e.g. cystic fibrosis). Impaired absorption of fat may also accompany a variety of intestinal diseases such as coeliac disease, and may be a problem following surgical removal of a large part of the intestine.

^†The prevalence of vitamin E deficiency due to malnutrition is significantly less than for vitamin A, as vitamin E is found in a broad range of dietary sources.¹