A mother-of-two had "extensive amputation surgery" after a hospital trust failed to recognise and treat her sepsis sooner, an investigation found.
Sadie Kemp, 35, spent 103 days in hospital after falling ill on Christmas Day but signs of sepsis were not initially investigated.
Ms Kemp, from Sawtry, said it was "vital lessons are learned".
The trust which runs Hinchingbrooke and Peterborough hospitals said an inquiry was ongoing into Ms Kemp's care.
Since her diagnosis Ms Kemp has had all 10 fingers amputated and her legs at the ankles.
Ms Kemp, who has been sharing her story on TikTok, had gone to A&E at Hinchingbrooke Hospital with severe back pain but was sent home and told to return the next day for tests. However, she returned hours later in the early hours of Boxing Day having deteriorated at home.
Later that night clinicians noted a deterioration in her condition but there was no evidence of a sepsis screening being performed for another three-and-a-half hours, the report said.