Brain damage or poisoning are much, much less likely than simply having a bad trip, which can have PTSD-like symptoms. But if set and setting are carefully controlled, bad trips are much less likely to occur, as you have no overly negative stimuli to induce a bad trip.

It’s rare with LSD but occasionally they’ll substitute a research chemical with similar effects. You’re more likely to have that happen with “MDMA” that is actually methamphetamine or one of the analogues. Both are horrible.

There are places that sell home testing kits which are very useful since you don’t know what you’re getting by looking at it. People used to test for each other at raves until the police said it was a form of condoning drug use and shut it down. So now people still buy but it’s more dangerous.

It's ludicrously expensive (I think I paid $3,000 for six sessions), but I've done a round at a local IV ketamine infusion center here in Chicago to great effect.

there are test kits you can buy - buying on the darknet is similar to ebay - there are reviews and seller ratings etc

if you are really struggling, cost is prohibitive, and you think this might be an option then trying it once or twice at home is reasonable risk reward tradeoff, speaking from personal experience.