Haematocrit
The Haematocrit or HCT also known as the packed RBC volume.
This measures the amount of your blood that is occupied by red blood cells (usually the volume of red blood cells in 100 ml of blood) or if you prefer a more technical explanation, 'a measure of the total volume of the erythrocytes in relation to the total volume of whole blood in a sample'.
Normal range
Results can be expressed in a number of ways. The older, or archaic way (as it is often called) is as a percentage. It is now more often expressed as a 'proportion of 1' sometimes with just the number (eg. 0.51) or with a 'volume unit' suffix (eg 0.51 L/L)
Newborn Range - 0.5 to 0.62 (50-62%)
Child - 0.33 to 0.40 (33-40%)
Adult male - 0.39 to 0.51 (39-51%)
Adult female 0.34 to 0.46 (34-46%)
What abnormal results mean:-
Decreased HCT levels may indicate:-
a) Anaemia eg from iron deficiency.
b) Massive blood loss (haemorrhage)
c) Bone marrow failure (for example, due to radiation, toxin, fibrosis, tumours)
d) Hemolysis (RBC destruction) related to transfusion reaction
e) Leukaemia
f) Malnutrition or nutritional deficiency eg. of vitamins and minerals.
g) Multiple myeloma
h) Rheumatoid arthritis
i) Cirrhosis of the liver
j) Pregnancy can cause slightly decreased values due to extra fluid in the blood.
k) Women may have temporary decreases during menstrual periods.
l) May indicate low thymus function.
m) Hyperthyroidism
Increased HCT levels may indicate:-
a) Polycythemia vera
b) Congenital heart disease
c) Increased R.B.C. breakdown in the spleen
d) Severe dehydration eg, from burns or diarrhoea
e) Adaptation to high altitudes.
f) Inadequate lung function eg due to smoking or lung diseases.
g) Shock.
Important note for diabetics
Low Hematocrit may cause the HgA1c test to give a false low.
High Hematocrit may falsely elevate the results of the HgA1c.
Back to top