The coma, such as vomiting or headaches

Events leading up to the coma, such as vomiting or headaches
Details about how the affected person lost consciousness, including whether it occurred suddenly or over time
Noticeable signs or symptoms before losing consciousness
The affected person’s medical history, including other conditions he or she may have had in the past, such as a stroke or transient ischemic attacks
Recent changes in the affected person’s health or behavior
The affected person’s drug use, including prescription and over-the-counter medications as well as unapproved medications and illicit recreational drugs
Physical exam
The exam is likely to include:
Checking the affected person’s movements and reflexes, response to painful stimuli, and pupil size
Observing breathing patterns to help diagnose the cause of the coma
Checking the skin for signs of bruises due to trauma
Speaking loudly or pressing on the angle of the jaw or nail bed while watching for signs of arousal, such as vocal noises, eyes opening or movement
Testing reflexive eye movements to help determine the cause of the coma and the location of brain damage
Squirting cold or warm into the affected person’s ear canals and observing eye reactions
Laboratory tests
Blood samples will be taken to check for:
Complete blood count
Electrolytes, glucose, thyroid, kidney and liver function
Carbon monoxide poisoning
Drug or alcohol overdose
A spinal tap (lumbar puncture) can check for signs of infections in the nervous system. During a spinal tap, a doctor or specialist inserts a needle into the spinal canal and collects a small amount of fluid for analysis.