The only way to tell with reasonable certainty of what you're getting is to have the product tested, ideally at multiple independent, high quality laboratories. Even then, if you're testing blotter or microdots, you're only going to know about the ones you tested, not about the rest of the batch. Properly shaken/stirred liquid should be better in that if one drop tested fine, the rest should be the same. But even then, if the substance easily separates out in the solution, you can't trust that either.

If anyone with a deeper knowledge of chemistry could speak about the effectiveness of testing, that would be welcome.

For testing, the only effective technique is GC/MS. But there is only one lab [REDACTED] knows of, which is the Spanish lab Energy Control. Unfortunately they are not always competent and often make routine errors in analysis.

LSD might not, but some toxins or impurities might, and those are the ones you most want to pick up in your test. So if you test just an unmixed portion, you might miss the impurities that are nonetheless there.

Here drug lab, I have an illegal drug. Can you test it for me and tell me if it is really the illegal drug I wanted?

"EcstasyData tests ecstasy tablets, powders, research chemicals, new pschoactive substances, and other street drugs through our DEA-licensed laboratory."[3]

You can also buy testing kits[4] for some drugs, like ecstasy, and do the testing yourself.

Looks like there is a test kit for LSD even.[5]

"Ehrlich's Reagent is a solution of hydrochloric acid, ethanol and p–dimethylaminobenzaldehyde. It can be used to positively identify LSD, helping rule out 25i-NBOMe, a highly toxic and extremely dangerous drug that is often misrepresented as LSD. Ehrlich's can also be used to identify other indoles. Contains enough reagent for approximately 50 tests."

I'm not sure if ruling out 25i-NBOMe is enough, though. Could there be other toxic substances that aren't caught by this test?

Still, some testing is much better than no testing.

[1] - http://www.ecstasydata.org

[2] - https://dancesafe.org/about-us/

[3] - http://www.ecstasydata.org/about_data.php

[4] - https://dancesafe.org/shop/

[5] - https://dancesafe.org/product/ehrlichs-reagent-testing-kit/

A little knowledge goes a long way, however. Tabs can only fit hundreds of micrograms to around a milligram (maybe a few mg's) on a standard sized blotter tab. This narrows down the # of potential active compounds massively. Also, LSD is active when swallowed immediately but nbomes aren't. So for a knowledgeable user it's not hard to avoid nbomes, but you will never be able to find out how much LSD is actually on your tab.

LSD might be pharmacologically active immediately, but not perceptually. It might take a while for the user to be sure they haven't eaten plain paper. Anyway, what is the "knowledgeable user" supposed to do when the substance they've taken isn't active immediately? Spit it out? By then it's too late. I really don't understand how this knowledge is supposed to help you avoid nbomes.

"you will never be able to find out how much LSD is actually on your tab"

Knowing what you're getting is great, but of secondary importance to making sure you're not getting poisoned.

The government should really step in, legalize it, and inspect the manufacturers and require testing, much like what is done in the legal medical industry now, with legal pharmaceuticals.

That process is itself currently far from perfect, and occasionally there are safety scandals even with legal pharmaceuticals, but it's still far better than the situation with illegal drugs now, when users have to seriously worry that their next dose will kill them because of potential toxic impurities that would all likelihood not be there if the drug was legal.

It's really upsetting that the government can stand by and just watch people suffer and die when they could be doing something to prevent it.