The website is calling on people in England who have recovered from the virus to donate plasma - which contains antibodies that are used to help fight infection - as part of a potential trial to treat Covid-19.
The trial, which has not yet been approved, will help scientists determine how effective convalescent plasma (that is plasma from people who have had had coronavirus) is for treating patients currently ill with the disease.
Those who have had a positive Covid-19 test or who have had symptoms can register, although not everyone is eligible to donate.
Plasma donation takes around 45 minutes and uses a process called apheresis that separates plasma from the blood. There are 23 blood plasma donation centres across major towns and cities in England.
To qualify to donate blood plasma, you must:
Be between 17 and 66 years old
Weigh between 50kg and 158kg
Not be pregnant, or had a baby, miscarriage or termination within six months
Not have an existing or previous heart condition
Not have had a transfusion since 1st January 1980.
What is convalescent plasma?
According to the NHS Blood and Transplant website, blood plasma "is a yellowish liquid that makes up about half your blood volume. "
After a virus, the plasma contains antibodies that are used to help fight infection.
"Convalescent plasma is the antibody-rich plasma of someone who has recovered from a virus, in this case COVID-19," the website says.
Coronavirus: Everything you need to know