Firefighters were called to a flat amid reports of a gas leak.
When they arrived at the property on Belmont Road, Hindley, at 5am on Sunday, paramedics were already there treating a man and a woman.
The crew from Hindley fire station used gas detection equipment but did not find any trace of gas.
However, the flat was very warm and it is thought the woman had fallen ill due to a diabetic condition.
She was taken to hospital for treatment.