The Sarah took to her Instagram account to share the devestating news with fans today.
Sarah, 38, has revealed she was diagnosed with breast cancer early this year and it has further spread to other parts of her body.
The star says she is undergoing chemotherapy sessions and "fighting as hard as I possibly can."
Addressing her 126k Instagram followers, she writes:
“I hope you are all keeping safe and well during these uncertain times,” continuing
"I’ve not posted on here for so long, thank you to everyone who has reached out to check in on me, it really does mean a lot’.
The reason she went on to explain adding "I feel now is the right time to share what’s been going on. There’s no easy way to say this and actually it doesn’t even feel real writing this, but here goes."
"Earlier this year I was diagnosed with breast cancer and a couple of weeks ago I received the devastating news that the cancer has advanced to other parts of my body.
"I’m currently undergoing weekly chemotherapy sessions and I am fighting as hard as I possibly can.
"I understand this might be shocking to read on social media and that really isn’t my intention. But last week it was mentioned online that I had been seen in hospital, so I feel now is the time to let people know what’s going on and this is the best way I can think of to do so.
Sarah adds thanks to family, friends and the NHS saying "My amazing mum, family and close friends are helping me through this, and I want to say a thank you to the wonderful NHS doctors and nurses who have been and continue to be heroes.
Tagged in Girls Aloud Sarah Harding