By Dr Luisa Dillner/London
Only 4% to 6% of the population gives the blood that the rest of us, if involved in a car accident, would rely on. Tomorrow is World Blood Donor day – a great time for new donors to step forward, so here are the facts.
How much blood gets taken?
Around 450ml to 500ml – including samples for testing.
What does your blood get tested for?
HIV, hepatitis B and hepatitis C, human T-lymphotropic virus and syphilis. The tests are done automatically to make sure blood is safe. If you have been to a country where malaria and trypanosmiasis are prevalent, your blood will be tested for blood-borne diseases such as sleeping sickness.
Who can give blood?
Anyone who is fit and well and over the age of 17 – as long as they are not pregnant, weigh over 50kg and have not had a tattoo or piercing, or had jaundice in the past six months, or travelled to an area which has malaria in the past six months. New donors must be 65 years of age or under. You should also only give blood once every 16 weeks. you should never give blood if you have ever had syphilis, HTLV (Human T‑lymphotropic virus), or hepatitis B or C.
What is most blood used for?
To top up people who are anaemic, for those who have lost blood during orthopaedic surgery and to treat people who have blood disorders.
Why do some people feel faint after giving blood and why does weight matter?
Dr Moji Gesindo, a consultant haematologist at Leeds Blood Centre, says that the average person can lose 15% of their blood volume without fainting. We have five to six litres of blood in our bodies depending on how big we are. If you don’t weigh enough then you could faint and so you need to be 50kg. Fainting is a physiological and sometimes a psychological process (so more likely among the squeamish). Eat beforehand and you will be offered a drink (of around half a litre) which research shows will sit in your stomach and keep your blood pressure up while you are having your blood taken.
What about if I am taking medication?
The blood transfused will contain very little of any medication. But you should say what you are taking. Some painkillers can stop blood clotting so you need to be off them for seven days before donating. If you are taking tablets for diabetes or high blood pressure you can give blood as long as you have been on the same dose for four weeks and are stable. If you are on antibiotics come back a week after finishing them, so won’t feel rough after giving blood.
How long does blood last for?
Thirty-five days in a fridge at 4°C. Some blood from very rare blood groups has to be frozen to keep for longer. — Guardian News and Media