Stock levels at the Newcastle Donor Centre have dropped due to recent staff and donor absence compiled with people being busy during the summer months.
Stock levels are vulnerable and could fall further without a rise in appointments.
The Newcastle donor centre is only 63% full for next week and only around 46% full the following week.
The lowest bloodstock is for O positive, with national levels at around three days, while the NHS seeks to have six.
Donors with this type are particularly needed, though donors of all types are welcome, especially O and B negative.
Demand for blood has also risen as hospitals catch up on the backlog of routine activity postponed due to the pandemic.
Hospitals are continuing to receive all the blood they need but more donation appointments are now needed to ensure stocks do not fall further.
Each blood donation can save or improve up to three lives.
Blood is used to treat patients with cancer, blood disorders and those suffering medical trauma or undergoing surgery
An NHS Blood and Transplant spokesperson said: “We currently have blood to meet demand but stocks have dropped and we need to stop them falling further - now. We urgently need more people to book appointments.
“If you are one of our amazing donors in Newcastle, or you want to donate for the first time, please make and keep an appointment for the next few days or weeks.
“If you used to donate blood but haven’t done so in a while, please come back if you can – our fantastic team at Newcastle Donor Centre will be delighted to welcome you. Every appointment counts.”