Ketamine shows up in urine for a couple of weeks maybe. A blood test would show it 24h - three days.

Hair tests are most reliable to check for long term substance use. From hair it would be detectable for months.

This is said to be a urine test, but cheating those is pretty trivial as well. The way urine tests work is that they just check the values and if your value of a certain drug is under a certain threshold, even if some is detected, it's counted as a negative. So if you drink tons of water, you can dilute your piss, making it less likely that the test will flag any metabolites in your pee. However, to counter this, labs also test your creatine value, which is an indicator if you've diluted your pee or not. However, to fool that particular check, all you need to do is take a creatine supplement, so you'll have too high levels of creatine, but when you dilute your piss, they'll be on the normal level. So the piss will be extremely diluted, while still having a "normal pee" creatine value, making the tester think it's good, while it's actually not.

So this genuinely proves jack shit. I mean, if it's not faked in any way, then what it "proves" is that Elon isn't a 247 weeder and has been without hard drugs for like, half a week. And that really isn't a sign of not being addicted, desperately trying to prove you're not the junkie people say you are by being sober for the better part of one week after the whole world has turned on you and everything you own is going to shit.

If you only consume occasionally pretty much all of those substances are only testable 1-3 days after consuming them, if you're a regular user it's usually between 5-7 days maximum.

As a regular user Ketamine could be tested up to 14 days in your urine. THC has the longest timeframe with up to 60 days when you use regularly.

Will share what I know, but for the record I'm a layman - any toxicologists in the house?

Depends on the compound, dosage, frequency of use, sample type, and test method. A screening immunoassay, for instance, will usually have a higher cut off than an LC-MS/MS (liquid chromatography tandem mass spectrometry) test. Good rule of thumb for your typical urine drug of abuse screen is 2 to 3 days, but again this varies (THC, for instance, can be detected for a loong time depending how big a stoner you are/how long you've used).

The stuff folks are mostly worried about re: Elon? About 2-3 days, assuming the typical urine DoA screen.

Now, you can also test other sample types (hair, nails, etc.), and in which case some compounds are detectable for much longer (90 days, etc.). But that window is also impacted by stuff like (in the case of hair, for example) how much hair is collected, where it's collected (scalp v. body hair), how long after last use it's collected, etc.

Even the ones on his balls?

(Sort of kidding, though fr I'd prefer a body hair collection anyway)