Factors affecting normal red cell values

Factors that determine 'normal' red cell parameters include:

• age:
  • in neonates, delay in cutting the umbilical cord elevates red cell levels
  • the haemoglobin level is high at birth
  • the haemoglobin falls before increasing again towards the end of the first year
  • the numbers of red cells then remains reasonably stable at about 11.5 g/dl, attaining normal adult values at about ten years
    
    
• sex:
  • haemoglobin concentration is higher in men than women
  • this may be due to stimulatory effects of androgens on erythropoietin production and a direct effect on erythroid stem cells
    
    
• menopause, childbirth and pregnancy lead to lower erythrocyte counts
  
  
• nutritional status:
  • parameters lower in poorer people
  • associated with protein and iron deficiency
    
    
• residential altitude:
  • high altitude associated with a compensatory increase in erythrocyte count