Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services or a poison centre immediately if an overdose is known or suspected.
Emergency signs include:
Difficulty waking the person
Slow, shallow, irregular, or stopped breathing
Blue, grey, or unusually pale lips or skin
Collapse, coma, or a seizure
Severe confusion or inability to stand
Suspected intentional overdose
Phenobarbital taken with alcohol, opioids, or other sedatives
If they are not breathing normally, begin CPR and follow emergency instructions.
Bring the medicine container or a photograph of the label to the hospital, but do not delay getting help to find it.
Routine follow-up is appropriate after emergency treatment for medication review, seizure care, or support related to the circumstances of the overdose.
And for anyone, someone who:
is unconscious, or cannot be woken
you believe has taken an overdose or swallowed something poisonous
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
2
Is any of this happening?
Be seen today
Do not wait for symptoms.
If you are in the United States, Poison Help is available at 1-800-222-1222.
Elsewhere, use your local poison information service.
New breathing trouble, worsening drowsiness, fainting, or confusion after discharge requires urgent reassessment.
3
Does any of this apply?
Book an appointment
And for anyone, someone who:
is having side effects from a medicine, or is struggling to take it as prescribed
The article also says
Do not leave the person alone or let them drive.
If they are unconscious but breathing, place them on their side if you can do so safely.
Every sign above is quoted from the sofidex article on Phenobarbital overdose. If you are not sure, err upward — it is always reasonable to be checked.