The Inverness actress is currently shooting for new movie Dual and told fans she needs to get tested for coronavirus regularly.
Each Monday and Thursday, the Avengers actress does a swab test to ensure she can continue filming.
In one of her videos, she can be seen struggling as she has a swab stuck down her nose.
She says, as she winces: “Oh I can’t, I can’t, I can’t, Oh I’m sorry! I can’t help it.”
In the next story, Karen makes light of the situation by making up a song about her tests with her co-star Beaulah Koale.
Sitting at a piano, she chants: “It’s a covid-test, covid test it’s a god damn mother f*****g covid test.”
She adds: “Oh Covid, I see you twice a week, every Monday and a Thursday, kinda like a game of hide and seek for the nose.”
Karen is currently shooting in Finland her new movie, a Sci-Fi about a woman who, after receiving a terminal diagnosis, opts for a cloning procedure to ease her loss on her friends and family.
When she makes a miraculous recovery, her attempts to have her clone decommissioned fail and lead to a court-mandated duel to the death.
She is filming alongside Breaking Bad actor Aaron Paul.
The 32-year-old got her big break as a sexy stripping police kissagram in Doctor Who has now been in films that have raked in £6billion.
Just this week, Karen invited Vogue magazine inside her plush LA home.
Showing off her fascinating office, she unveiled all the weird and wonderful memorabilia she has collected over the years from working in Hollywood.
Items included dolls of her movie roles, a puppet of her Marvel character Nebula, an infinity gauntlet from the Avengers films, a signed copy of The Exorcist movie poster and a Spice Girls Polaroid camera.
The Doctor Who star also proudly showed off her music skills on her vintage Steinway piano and said it was once her ‘big mission in life’ to buy one.
Karen landed the part of Amy Pond in Doctor Who, alongside Matt Smith, in 2010.
She has since appeared in a series of blockbuster movies including Avengers: Infinity War, Guardians of the Galaxy and Jumanji.