[thejeff]

Normally, yes. But not if you are in a province with a lab.

May be worth noting, if something as esoteric as removing cursed boosters by transforming is worth putting in the guide at all, that it's not just transforming pretenders.
I'm thinking specifically of Jotunheim's Skratti, who might have some use for an extra blood booster. And Gygja's can make them, too. Which is most convenient.