John Hatfield, 69, was undergoing long term treatment for a heart condition when he was admitted to hospital with bleeding following a side effect of his medication.
But, after a catalogue of failings by staff at the hospital he collapsed and suffered a cardiac arrest.
An inquest into his death heard Mr Hatfield died after staff failed to give him the life-saving blood that he needed.
His family said they wanted lessons to be learned after a narrative verdict found a catalogue of failings by staff led to his death.
Medical negligence lawyers at Irwin Mitchell, representing the family, said they had received have had an admission of liability from York Teaching Hospitals NHS Trust.
Mr Hatfield, from Heworth, York, was receiving treatment for Atrial Fibrillation - a common condition which causes irregular rhythm in the heart and affects around one in 20 adults over the age of 65 years.
He was admitted to York Hospital on 1st May, 2013, and swiftly diagnosed with a gastrointestinal bleed, a side effect of his anticoagulant medication Warfarin. Eight hours later he collapsed, suffering a cardiac arrest, after medical staff simply forgot to give him a life-saving blood transfusion.
After arriving on the Acute Medical Ward with chest pains and heart palpitations, he was not monitored by a nurse - or even visited by a doctor. After being left for nearly three hours alone on a ward, his low volume of blood caused a cardiac arrest and he never regained consciousness.
Mr Hatfield died on May 8 that year after his life support machine was switched off.
His widow Madeline, 71, said: “We simply cannot conceive how we could lose John so suddenly. One day he is at home happy, fit and able, the next day on a life support machine.
“To find out that he could have, and should have, easily survived leaves us devastated. In our opinion, it is not down to a lack of systems; it is that the systems and protocols were wholesale ignored.”
Katie Warner, medical negligence expert at Irwin Mitchell, said: “The past year has been horrendous for the family and for them to hear that John’s death was completely avoidable has left them devastated once again.”