Give them any information you have, at least as it pertains to whatever medical emergency they're attending.
Presumably this is about what drugs and alcohol you have consumed, in which case you should always tell them everything you can, including descriptions of the appearance of any drugs or if any alcohol you had tasted unusual or different. They aren't the police, they don't care what you took from a legal standpoint, they care what you took so they can prevent it from killing you (or prevent something they give you interacting with it and killing you).