A southern Alberta woman says she would like to help Canadian Blood Services (CBS) ease its blood shortage but she is not allowed to donate.

Sue Carpenter moved to Cochrane, Alta. from England nine years ago.

People who lived in the U.K., France, Saudi Arabia and Western Europe over certain periods of time can't donate blood.

That's because of concerns about variant ​Creutzfeldt-Jakob (vCJD), sometimes called the human equivalent of mad cow disease.

Carpenter is surprised screening practices haven't become more sophisticated since then.

"I just couldn't understand why I was able to give blood for so long in England and yet I couldn't do it here," she said.

"There are an awful lot of Brits that have come to live here and I'm just wondering how many people are being turned away from donating blood because of this."

Carpenter says she was a regular donor in the U.K. and has the universal blood type.

No licensed test available, says CBS

"All of our deferral policies are in place to protect patients and even donors," said CBS spokesperson Deb Steele-Kretschmer in an email. "But we realize it can be difficult for many well-intentioned people to understand why they are in place, or why they seem out-dated."

She said CBS is hoping to have a stop date for the five-year travel to Western Europe — so it would be 1980 to likely the end of 2007, rather than open-ended — but that change would have to be approved by Health Canada.

"There is no licensed test available worldwide to test for vCJD,... and the incubation period — that is, the amount of time before symptoms show up — is currently unknown," said Steele-Kretschmer, adding the blood agency is carefully monitoring the development of new technologies to either remove vCJD from blood, or test for the presence of the disease.

"We realize that many very committed, healthy blood donors are deferred as a result of this policy. Unfortunately, this is the price of ensuring the safest system possible, and trying to balance that safety at all times against an adequate supply."

CBS sounded the alarm earlier this week that its blood supply is the lowest it's been since 2008. The agency strives to have a five- to eight-day supply of blood on hand. 

Currently, the supply is down to three days.

Last year CBS and Héma-Québec loosened restrictions on donations from gay men so that they can now give blood if they haven't had sex with a man in five years.

The previous policy barred men from giving blood if they did had sex with a man, even once, since 1977. It was enacted in an attempt to keep HIV-infected blood out of the supply.