Title basically, will my body be too fucked up for my organs to be donated? Will I have to specify what chemicals I took?
If this could be possible I might go through the hassle of signing up for organ donation but I'm not really sure how likely it will be for my organs to be usable.
I actually looked into this myself awhile ago. It differs somewhat by jurisdiction, but very commonly only those who die in a hospital are permitted to donate. The reasoning is that vital organs quickly become unusable after the heart stops, and in a hospital environment the medical team knows the precise time of death, has records surrounding the cause of death and any potential disqualifying factors, can rapidly screen for the rest, and can take steps to optimally preserve the organs for transplant.
Successful postmortem transplants are a race against time. So unfortunately, unless your plan involves dying in a hospital it is very unlikely you will be able to donate. I do know that opioid overdoses do qualify for transplant in some situations, but again it has to be in a hospital. Exceptions are pretty rare I think, such as home care hospice programs that have pre-existing arrangements for immediate transportation to a hospital to allow donation.
It's a noble thought though. Imagine if we lived in a world that was more accepting of our decision, legally allowed assisted suicide in a hospital environment, and all the lives that could be saved through transplantation. It's a shame really.