I'm surprised this was not known before now. I have met several people with aid-dogs that can tell them when their blood sugar is very low. When asked, these people said the dogs can smell a problem.<p>I met one gent as a FIRST robotics world tournament that advertised on his dog what the dog's responsibilities were and encouraged people to ask questions. He said that the dog had saved his life several times and wanted to let others know what is possible.