If they are unconscious and breathing, nothing will happen. If they are unconscious and not breathing, they will die.
When a diabetic person becomes unconscious, check for their emergency glucagon injection kit, as you are calling 911. Once the person is conscious, treat the same as you would a person who has not been unconscious.
When the person does not respond
The powder that can make a person unconscious is called "बेहोश करने वाली पाउडर" in Hindi.
Depends on the person and situation.
chloroform
a unconscious person needs oxygen because without oxygen they will sufer serious brain damage and can possable die.
tap on their shoulders and repeatedly ask if they are OK. if no response they are most likely unconscious.
breathing
These substances are called narcotics.
taste
If a person is unconscious, it is important to call 911. Next, the airway should be opened by tilting the head back and up.