THE NHS is urging people to continue donating blood following a cyber attack that brought operations to a halt at major hospitals in London.
The cyber gang took control of the IT network, crippling services such as diagnostic blood testing.
Brits with O blood type are being urged to book appointments to donate.
O blood-type is important because it is 'universal' - regardless of a person's blood type, they can recieve a tranfusion with O blood in most cases.
Given the IT attack has prevented affected hospitals from matching patients’ blood at the same frequency as usual, O-blood type is in need more than ever before.
It comes after several London hospitals declared a critical incident, cancelled operations and tests, and were unable to carry out blood transfusions this week after the attack on the pathology firm Synnovis.
Qilin, a Russian group of cyber criminals, is understood to have been behind the attack, which impacted King's College Hospital, Guy's and St Thomas', the Royal Brompton and the Evelina London Children's Hospital, and primary care services.
NHS Blood and Transplant is now calling for all O-Positive and O-Negative donors to book appointments in one of London's 25 NHS donor centres to boost stocks.
The NHS said hospitals need to use O-type blood for surgeries and procedures requiring blood.
Blood has a shelf life of 35 days, so stocks need to be continually replenished.
To support London hospitals in carrying out more surgeries and to provide the best care we can for all patients, we need more O-negative and O-positive donors than usual.
Dr Gail Miflin
That means more units of these types of blood than usual will be required over the coming weeks.
Also, stocks are low following both May's bank holidays and the recent half-term.
O-negative is the type that can be given to anyone and is used in emergencies or when a patient's blood type is unknown.
Air ambulances and emergency response vehicles carry O-negative supplies.
Just eight per cent of the population have type O Negative, but it makes up for around 15 per cent of hospital orders.
O positive is the most common blood type; 35 per cent of donors have it, and it can be given to anybody with any positive blood type.
This means three in every four people, or 76 per cent of the population, can benefit from an O-positive donation.
Dr Gail Miflin, NHS Blood and Transplant chief medical officer, said: "To support London hospitals in carrying out more surgeries and to provide the best care we can for all patients, we need more O-negative and O-positive donors than usual.
"Please book an urgent appointment to give blood at one of our 25 town and city donor centres, which currently have good appointment availability.
"We have availability for donors who know they are type O, but we also welcome new donors who don't yet know their blood type.
"You might have one of these special types that can be used in emergencies."
Professor Stephen Powis, medical director for NHS England, said: "NHS staff are continuing to go above and beyond to minimise the significant disruption to patients following the ransomware cyber attack on Synnovis earlier this week.
"Urgent and emergency services are available as usual, so patients should access services in the normal way by dialling 999 in an emergency and otherwise using NHS 111 through the NHS App, online, or on the phone.
"But unfortunately, we know that several operations and appointments have been postponed or diverted to other neighbouring hospitals not impacted by the cyber-attack, as we prioritise pathology services for the most clinically urgent cases.
"To help London staff support and treat more patients, they need access to O-Negative and O-Positive blood, so if one of these is your blood type, please come forward to one of the 13,000 appointments currently available in NHS Blood Donor Centres."
For more information or to make an appointment to donate your blood at the nearest centre, click .
DONATING blood can be an amazing gift to people who desperately need it for on-going medical treatment or in an emergency.
But who exactly is eligible to provide a donation? Here is all you need to know...
Who can give blood?
Most people are eligible to give blood.
You can donate if you are:
Men can donate more often than women can.
How often can I give blood?
Men can give blood every 12 weeks, while women can donate every 16 weeks.
This is because it takes several weeks for all the red blood cells to be replaced in the body.
Over 6,000 people are needed to donate each day to meet the needs of hospitals, and there is a drive for to help black patients with sickle cell disease.
To make an appointment to donate your blood at the nearest centre, click .
What happens when you give blood?
Appointments to give blood typically last no longer than an hour.
1. Welcome and preparation
You will be given a leaflet to read and 500ml of fluid to drink just before you give blood. You'll be asked to drink it over a five-minute period to help ensure you don't feel faint or nauseous after donating.
2. Health screening
NHS staff will make sure it is safe for you to donate, and that your blood is safe for a patient to receive.
3. Giving blood
Once you are comfortable in a chair, staff examine your arm to find a suitable vein and clean it with antiseptic.
A needle will then be inserted into your arm, which will be used to collect your blood into a blood bag with your unique donor number.
You shouldn't feel any discomfort or pain.
If you do, tell a member of staff.
A scale is then used to weigh the blood you have donated, and stops when you've given 470ml.
This usually takes between five and ten minutes.
The needle is then removed and a dressing is put on your arm.
