Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Treat a suspected overdose as an emergency.
Call your local emergency number immediately if someone:
Use naloxone if opioid overdose is possible, but do not delay the emergency call.
Begin CPR or rescue breathing if instructed and if you are able.
Elsewhere, use your local poison service or emergency number.
And for anyone, someone who:
For a possible dosing mistake without symptoms, contact a poison information service promptly.
Do not wait to see what happens, because some effects are delayed.
In the United States, Poison Help is available at 1-800-222-1222 .
After hospital treatment, seek urgent reassessment for increasing sleepiness, trouble breathing, repeated vomiting, fainting, seizures, chest pain, yellow skin or eyes, severe abdominal pain, or worsening confusion.
Routine follow-up is appropriate for medication review, repeat laboratory tests, mental health support, or treatment for substance use after the immediate danger has passed.
And for anyone, someone who:
Every sign above is quoted from the sofidex article on Overdose. If you are not sure, err upward — it is always reasonable to be checked.