[OutOfHere]

I strongly advise keeping all supplements in a checked bag, with good written labels about what they are. I keep them in ziploc bags with very clear labels. For mixed stacks, write DAILY VITAMINS, DAILY PROTEIN, etc.

If you carry them with you while going through security, you're just asking to be strip searched and questioned.

[spidercat]

I can only speak towards TSA in the US, but they explicitly state that they do not search for drugs; their priority is to screen for explosives, weapons, things of that nature. Anytime I travel with my beloved Mystery Powder supplements, I always just put them in my carry-on luggage. I've lost count of how many times I've done this, and it's never been an issue, stateside and abroad.

Of course, all of the supplements etc I've traveled with have been very much legal and mainstream enough (e.g. creatine, magnesium), in case security do get suspicious, but it has not once been an issue.

[OutOfHere]

Even if that were true, if you carry bulk powders in your carry-on, at minimum it is their assumed responsibility to visually examine it for not being an explosive powder. I have had to remove these powders from the carry-on bag for them to see. After seeing the labels, they consulted a senior officer, and only then let me through. For this reason, if I have a check-in bag, I keep it there.

[spidercat]

Oh, I probably should have mentioned that I almost always keep my powders capped - I just cap them myself at the doses I need. Keeping the powder loose probably does raise more flags. I'm just so used to capping them, I didn't even think about how sketchy loose powder in ziploc baggies could look.