Stocks have been affected by staff and donor absence due to illness and the drop in donations over summer when people are busy with holidays and events.
Stock levels are vulnerable and could fall further without a rise in appointments.
However the Nottingham donor centre is only 45 per cent full for next week and only around 30 per cent full the following week.
The lowest blood stock 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 Nottingham, 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 Nottingham Donor Centre will be delighted to welcome you.
"Every appointment counts.”
Nottingham has a permanent blood donor centre at Trinity Square on Northchurch Street.
There are also mobile sessions available.
Click here or call 0300 123 23 23 or download the NHS Give Blood app.
For more information about giving blood, visit the website here.