Absolutely. There is a large body of anecdotal evidence for this in the service dog community. Dogs trained to bring a "case" on command quickly associate (smell of ketones?? - mechanism is unknown) and bring the case when needed, prior to the individual realizing it themselves. There have been multiple reported instances when dogs have awoken their companions from sleep - a very dangerous time for a diabetic - to alert them of their need.
There is an entire community around training "alert" dogs for diabetics, cardiac alert, seizure alert, etc.
(I have not kept up with the literature recently, but I would assume that studies have been or are being conducted around these abilities.)
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