Should I bring the suspected poisonous item to the ER with me?

Yes you can, as long as it is safe to do so.

For example, if you have been bit by a suspected poisonous snake---do not go back and pick it up and bring it in! (You do not want to be bit again). Or carrying a leaking toxic bottle of a chemical in your auto would not be safe either.

If there is a safety concern like a poisonous inhalant or toxic chemical it may be in your best interest to call the fire department and emergency medical service for assistance and immediate decontamination

However if the offending agent is a bottle of pills or a household chemical in a safe and secured jar or can and it would be safe to transport it then by all means do so. This may help save time in treating the exposure if it can be readily identified.