Plasma donations are currently being taken at the JR Hospital in Oxford.
The number of people receiving plasma as a treatment for COVID-19 has quadrupled in the last month.
Around 220 hospitalised patients were treated in September as part of clinical trials that began in May.
The RECOVERY trial by Oxford University is looking at whether convalescent plasma works as a treatment for COVID-19.
Deputy Chief Medical Officer, Professor Jonathan Van-Tam, said: “I urge people to do two things. One, to consider volunteering for clinical trials. These are the only way to obtain really high quality evidence about what works and what doesn’t. RECOVERY did this with dexamethasone, which is now saving lives globally.
"Two, for those who have had COVID-19, and are eligible, to donate plasma so it can be trialled, and if it is shown to work, to be used as a treatment. We need to build up the amount of plasma we have now, so it can be used in the future. Both of these are concrete actions you can take and possibly save someone else’s life.”
People who have had coronavirus produce antibodies that are present in their plasma - if transfused to a COVID-19 patient who is struggling to develop their own immune response, there is evidence that it could help them recover.
NHS Blood and Transplant currently holds enough units of donated plasma for the trials - but is building a stockpile that is ready to be used immediately if the trials succeed.
The NHS currently has enough units to treat about 4,000 people and is appealing for more donations.
Sheila MacLennan, clinical lead for the Convalescent Plasma Programme, believes the increase in treatments is due to more hospitals participating in the trials and an uptick in coronavirus cases.
Plasma donations from COVID-19 survivors are being collected at NHS Blood and Transplant's 23 donor centres around the country, including one at the John Rdacliffe in Oxford.
London, Greater Manchester and Birmingham are priority areas for donations.