PLASMA donors are being urged to come forward in Reading, after around 140 appointments are going empty every week.
The donor centre, on Kings Road, is at just 40% capacity each day.
And the NHS is reaching out to social media and public places as part of its campaign to get more volunteers.
Paula Ussher, Reading Plasma Donor Centre manager, said plasma is a “powerful, lifesaving part of our blood”.
“Since donation restarted we’ve had many fantastic people come in to donate but we still see too many empty chairs every day,” she said. “We need your help.”
Plasma is used to make medicines full of donor antibodies which fight infections.
The medicine, immunoglobulin, is used to strengthen the immune systems of people with life-threatening diseases.
Ms Ussher added: “In the next few months, we need thousands more people to start donating at our donor centre.
“Plasma donation is safe and easy, it doesn’t take long, and you will help save and improve the lives of some of the most vulnerable people in the country.”
The campaign, headlined “the medicine in you”, will emphasise that for some patients there is no alternative treatment is available.
To donate, call 0300 123 23 23, or log on to: blood.co.uk/plasma