Lisa Rinna thinks she was drugged with something at "The Traitors" Season 4 premiere party on January 8, TMZ has learned.

Sources familiar with the situation tell us ... Lisa's 'Traitors' co-star Colton Underwood noticed Lisa was completely inebriated. Because Colton says he knew Lisa didn't have that much to drink -- he was with her the whole night -- so he became concerned, according to our sources.

We're told Colton notified Lisa's team, who got her out of there after a group pic.

Colton coming to Lisa's rescue may surprise 'Traitors' fans who watched him and Lisa go at each other towards the end of their time on the Peacock reality show. And after the show wrapped filming and started airing, Lisa has at times said they were friends, but has also brought up allegations from Colton's ex-girlfriend, Cassie Randolph, that he allegedly stalked her and put a tracking device on her car.

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At a book signing for her new memoir a couple of days ago, Lisa teased that she may have said something that upset Colton at the 'Traitors' reunion, which caused him to unfollow her on socials.

As the premiere was more than a month ago, their on-again, off-again friendship may be off at the moment.

It's unclear if police were involved in this incident or if Lisa went to the hospital.

We reached out to Lisa’s reps for comment as well as Colton's ... so far, no word back from either.