The Duchess of Cornwall opened the new Medical Detection Dogs (MDD) training centre near Milton Keynes today.
Medical Detection Dogs was founded in 2008 by Dr Claire Guest and Dr John Church, who believed that dogs' powerful noses could help detect disease.
Her Royal Highness has been Patron of the charity since 2014.
The Duchess met Elizabeth Draper, 23, who suffers from postural orthostatic tachycardia syndrome (POTS), and has had Labrador Henry for almost a year.
She said: "When I'm standing up or upright, my heart rate rapidly increases and my blood pressure drops which causes me to black out."
"Henry will alert to my black-out, and also extreme palpitations and dizziness.
"He can let me know about five minutes before. He'll jump up at me, and if I'm really not paying attention he will bark at me."
Having been trained with sweat and breath samples from Miss Draper, Henry can detect changes in her body and lets her know she could be about to fall unconscious.
The charity now train medical alert dogs to work alongside people with health problems such as diabetes and nut allergies, as well as other specialist dogs who can detect diseases such as cancer and Parkinson's.
The Duchess saw a wide variety of the charity's facilities, including puppy training and a veterinary room, and eight of their dogs performed a guard of honour as she cut the ribbon to officially open the new centre.