The NHS has apologised for the death of a Torquay woman after she was given the wrong treatment for deep vein thrombosis.
Lisa Gilbert was admitted to Torbay Hospital on her 49th birthday but died two days later, in January 2009.
Her family told BBC News that "it has totally devastated us all".
A South Devon Healthcare NHS Foundation Trust spokesperson said the hospital had admitted liability for medical negligence.
Mrs Gilbert's family said she was admitted to hospital after her GP suspected a pulmonary embolism resulting from DVT.
The family said medics at the hospital treated Mrs Gilbert for a number of different conditions instead of DVT.
Joanna Gilbert, one of her three daughters, said: "They missed all the vital warning signs that were pointing to DVT, such as hyperventilating and panic attacks."
She added: "It breaks my heart to have lost her so unnecessarily. I hope this never happens to anyone else."
South Devon Healthcare NHS Foundation Trust confirmed the incorrect treatment was given to Mrs Gilbert.
A spokesperson said: "This was a tragic incident and we have offered our sincere apologies to Mrs Gilbert's family."
The trust said lessons would be learnt and new procedures were in place to prevent a similar incident happening.