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Jackie Fuchs, the former Runaways bassist and reigning queen of 'Jeopardy,' had a major health scare while taping the show ... and it was so bad, she thought she was having a stroke!

Jackie tells us midway through the latest 'Jeopardy' contest her blood sugar levels crashed, causing her to lose control of her motor functions. She says the studio audience absolutely noticed too, and even groaned as she was struggling to speak.

If you've been watching Jackie dominate her 'Jeopardy' competition, you know she's on a four-night win streak heading into Thursday's episode. Jackie says her medical emergency will most likely be edited out. Meanwhile, she's just trying hard not to reveal anything about the final result.

'70s music fans: Does Jackie look familiar to you? pic.twitter.com/hu11Oc20EN @Jeopardy

Jackie's win streak on the show started last Friday, but it wasn't until this week Alex Trebek revealed her rock star past with Joan Jett's all-female rock group.

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Jackie's clearly feeling better now ... because we had one of our staffers -- who considers himself a trivia expert -- challenge her.