RED BLOOD CELLS AND WHITE BLOOD CELLS The questions below were raised by visitors to the STOMP (Straits Times Online Mobile Print) website in the AskST section of the website. eMenders doctors provided the answers to the questions raised as a public health education project. The information provided below is of a general nature and should not be treated as a replacement for medical advice. You should seek consultation from a medical or healthcare professional about your specific medical condition.
Question:
How many red and white blood cells are there in our bodies?
Answer:
In a normal healthy person, there are an estimated 5 000 000 000 000 red cells in one liter of blood. This would read 5 Trillion/L in America, and 5 Billion/L in Britain. About 7% of the body weight is blood. Thus, a 65 kg individual would have 4.55 liters of blood.
Therefore an average person weighing 65 kg would have 4.55 x 5 000 000 000 000 red blood cells, or 22.75 Trillion (American units).
It is a little more complicated with normal white blood cells. Assuming an average white blood cell count of 7000/µL of blood, we should have as many as 7 000 000 000 white cells per liter of blood, or 7 billion/L. (American Billion).
However, as many as 50% of white blood cells are not circulating in the blood stream, and are “marginated” at the walls of blood vessels. Using the formulae above, we conclude that there are 6 360 000 000, (6.36 American Billion) circulating white cells.
DR. RONALD NG is a Consultant (Haematology) at the Mount Elizabeth Medical Centre.