Gothenburg is the area with the most serious shortage, and members of the public have been urged to donate blood at healthcare centres in the city. The biggest shortages are for blood groups O+ and A+.
One potential reason for the shortage is a recent wave of knife attacks in the city, according to Jan Holgersson who works at Sahlgrenska University Hospital.
"It can be trauma cases like the stabbings recently, but it can also be [due to] traffic accidents, major operations, or patients with blood disorders," he said.
Uppsala and Gävle have also reported low levels of blood, although unlike in Gothenburg the situation in these areas is not classed as an extreme shortage.
Another reason for the shortage is the summer holidays. Blood can typically only be used for up to six weeks after donations, and with many Swedes taking lengthy holidays over the summer season, regular donors are less likely to donate at this time.
In most areas it is currently only possible to give blood if the donor has sufficient knowledge of the Swedish language, and it is up to the nurse to assess the donor's level of understanding.
But a Blodcentralen clinic in Stockholm this year for the first time made it possible for English-speakers to also donate blood, after translating the relevant health declaration documents into English.