Dory, a one-and-a-half stone rabbit, jumped up on 42-year-old Simon Steggall as he began to slump into a diabetic coma while sitting on his settee watching televison.
Wife Victoria, 32, thought he had simply fallen asleep after a hard week at work and it wasn't until Dory started thumping on his chest she realised something was terribly wrong.
Ambulance driver Victoria immediately swung into action and rubbed a special gel into Simon's gums to try and bring his blood sugar levels back up to normal.
But when that failed she rang 999 for paramedics who injected the BT engineer with medication to force his liver to dump its store of glucose, which finally brought him round.
A relieved Vicky said: "I work for the ambulance service and I'm embarrassed the rabbit spotted it before I did."
Husband Simon added: "I don't know how she did it, but Dory saved my life.
"I was watching television and Vicky thought I had gone to sleep.
"The rabbit came up on my lap and started tapping and digging at my chest and looking at my face. That caught Victoria's attention and she realised something was wrong."
Simon has been a type one diabetic since he was four and needs to inject himself four times a day and do blood tests five times a day to make sure his blood sugar levels don't fall too low.
Vicky was in the kitchen of her home in Warboys, near Huntingdon, when she was alerted by Dory scratching at her husband's chest.
She said: "She was licking round his face and was not at all happy.
"I wouldn't have spotted it as quickly as she did, bless her."
It's not the first time that a pet of Simon's has come to the rescue.
He used to own a black labrador who would cower in a corner whenever Simon's blood sugar levels began to fall to dangerous levels - alerting him to the fact that he needed to do a blood test.
The couple have had Dory - named after the stupid fish in the Disney blockbuster Finding Nemo which they went to see with children James, 12 and 10-year-old Daryl - for four months.
The family also have a Dalmatian dog and three cats - as well as two other rabbits, two guinea pigs and an eagle owl.
