This is what the blood donor service does after an attack – and how you can help | Jane Green

I was overwhelmed by how generously the people of Manchester responded to this horrific attack. Both our blood donor centres in Manchester had queues outside the doors before they even opened. Our national call centre was taking about 1,000 calls an hour by 10am, from people who wanted to help save lives by donating blood.

The response was driven by well-intentioned social media posts from the public. The desire to help was incredible. However we already had enough blood to supply the hospitals treating the victims, and we did not appeal for extra donors. We plan ahead to build in reserves to deal with major incidents. We hope that people who want to help will now become regular donors, because that is how they can best help us save lives when there is a tragedy.

Many people wanted to donate to help that day, but when you donate blood, it is not taken straight to a patient. We need time to test it and process it. The different components such as platelets and red blood cells need to be separated out. Typically, your blood donation will only reach a patient two or three weeks after you donate. The blood used to treat the Manchester victims would have been donated several weeks earlier, and those donors would have been from across the country.

Hospitals order blood from us in advance, without the need for blood to be brought in for each patient. We supply hospitals through our regional stock-holding units (what people refer to as “blood banks”) mainly through routine deliveries. Over Monday night we made 21 deliveries of blood to hospitals in Manchester, including 15 “blue light” emergency deliveries, delivering 346 units of red blood cells. We were able to meet all the hospitals’ requests, and our stocks remained good. We don’t know exactly how this blood was used, and much of the blood from the routine deliveries would have gone to patients not affected by the attack. But this was an exceptionally high level of local emergency demand and many of those precious donations would have been transfused into attack victims.

Trauma patients require more than just red blood cells. They also need platelets to help their blood clot, and other more specialised products: O-negative blood is especially important in emergencies because it can be given to anyone when time is short and you don’t have time to test for blood groups. We always need new O-negative donors because their blood is so valuable.

As Tuesday morning progressed, people began queueing to donate. Some had friends or family members caught up in the incident. We were worried they might be confused or upset about why there was no capacity or urgent need for them to donate that day.

We tried to spread the message about how people could best help across social media and through the press. I was working at Plymouth Grove donor centre, next to Manchester Royal Infirmary, where many victims were being treated, and I spoke to many people face to face. We were inspired to see the diversity of people coming forward, which was moving and very important – because we need more black and Asian donors. Patients benefit from closely matched blood, which will often come from donors of the same ethnicity.

Our message is that blood can best save lives in a tragedy when our stocks are already good through regular donations. Thanks to our loyal army of nearly 900,000 active donors, many of whom give blood three or four times a year, we can do that. But every year many of these donors have to drop out because of age, ill health and many other reasons. We need nearly 200,000 people to register as new donors every year.

If people have been inspired to donate for the first time, please go online, make an appointment, and donate. Blood saves lives, and your donation will help other people in urgent need, and make sure we are again ready for any major incident.