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.