Blood donors are being urged to help increase vital stocks before Oxford Blood Centre reaches crisis levels.
A surge in operations has left the city's National Blood Service unit with depleted supplies.
And the problem has been compounded by the beginning of the holiday period, with many regular donors missing new sessions because of holidays and days out.
National Blood Service spokesman Carlene Dias said: "Attendance is dropping quite considerably because we are coming into the holiday season.
"The demand for blood from hospitals is high at the moment so it is a bit of a double whammy for us, It is a case of appealing for more donors."
Stocks have been dropping rapidly since the May bank holidays, which created a downturn in attendance.
The National Blood Service is always happy to enlist new donors. Anyone in general good health and between the ages of 17 and 60 can volunteer. More information is available by calling the hotline on 08457 711711
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