She commented: "Funny that. I am studying to be a psychiatrist. I could help with another kind therapy (in possibly 10yrs)."
Fans rushed to congratulate the Londonderry-born singer on her new path, but some questioned if she was being serious.
She teased that she had hopes of becoming Dr Coyle, with the hashtag "MedicaldegreehereIcome". Although she did not release details of where she is studying, the 30-year-old was spotted in Ireland over Christmas and the New Year.
But she will not be abandoning music altogether as she ended the post with, "ps I'm still a singer", hinting that she will continue her solo career alongside her studies.
Nadine released her first solo album Insatiable in 2010 while Girls Aloud were on a break, but both the album and eponymous single flopped.
The single peaked at 26 in the UK Top 40, while the album only made it to number 47 in the charts.
Since the band split in 2013 Nadine has continued to work on her own music. Just last year she released I Could Be with former Westlife star Shane Filan and she told eager fans that she was hoping to release her own music this year.
Nadine found fame in 2002 on the second series of Popstar: The Rivals, winning a place in the five-piece girl band.
They went on to have 20 consecutive UK Top 10 singles, including four number ones, but then split for good three years ago following a 10-year anniversary tour.
Her recent announcement is not her first move away from music. She also bought a bar for her parents in California called Nadine's Irish Mist, but the pub faced problems in 2012 and it has since closed down.
She moved to America with her family 13 years ago where she met her partner Jason Bell, a former American football player.
In February 2014 the pair announced the arrival of their first child together, Anaiya Bell, and Nadine now splits her time between her home in the US, her work in London and her home town of Derry.
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