Pet dogs of type 1 diabetics can be trained to sniff out dangerous episodes of low blood sugar, the biggest study conducted so far has shown.

Researchers from Bristol University assessed the reliability of 27 dogs for between two and four months and compared their alerts to blood records kept by their owners each time the animal sensed something was wrong.

They found that on average the dogs correctly alerted their owners to 83 per cent of hypoglycaemic episodes in over 4,000 incidents. Some were able to predict an attack 60 minutes before symptoms began to show.

Hypoglycemia, also known as low blood sugar, can be extremely serious, resulting in in seizures, loss of consciousness, or death.

Usually insulin regulates the amount of sugar in the blood to prevent it becoming too low or too high, but in for people with type 1 diabetes the hormone is no longer produced in sufficient quantities.