MCV is derived from the Red Blood Cell (RBC) and Haemoglobin (Hb), another valuable parameter which is the ratio of Hb to RBC. The MCH represents the amount of Haemoglobin (Hb) per cell. This is a direct measurement on most FBC auto analyzers.

Causes associated with a High MCV:

• Vitamin B12 deficiency
• Folate deficiency
• Liver disease
• Alcoholism
• Hypothyroidism
• Some haemolytic anaemia
• Cold agglutinin disease
• Myelodysplastic syndromes/preleukaemia
• Aplastic anaemia
• Benign familial macrocytosis
• Some chemotherapy drugs
• Chronic hypoxia (low oxygen levels in the blood) such as with COPD with CO₂ retention
• Carbon monoxide poisoning

Causes commonly associated with a Low MCV:

• Iron deficiency (there are many different causes of iron deficiency anaemia)
• Thalassaemia (there are several types and it is thought to occur in around 30 percent of African Americans)
• Anaemia of chronic disease
• Sideroblastic anaemia
• Lead poisoning
• Hb C and other haemoglobin hybrids
• Spherocytosis