I bought it because I had a series of symptoms that possibly (according to what a nutritionist had told me) indicated a lack of B1. I had very restless sleep, constantly waking up tired, waking up multiple times during the night, constant nightmares, and in the mornings I couldn't stop thinking about various things even when I tried to relax, etc.

Anyway, I thought I had nothing to lose, it's around 10 euros for a bottle that lasts for months, it's just a vitamin and nothing strange.

I start taking one a day. After a week, I thought I took it for no reason, I didn't see any difference, it doesn't do anything. But since I paid for it, let me continue taking it for a little while longer. At 10 days, I start seeing results but I think it's just my imagination, probably just a coincidence. I note that I had the aforementioned issues systematically for months. Now, after 1 month of taking B1, I consider that it has helped me a lot.

I do the same "experiment" with two close people who had similar issues, especially with sleep. I give them vitamins for 2 weeks. I talk to them after 5 days, they tell me it doesn't do anything. I talk to them after 10 days, they both say "we went and bought it, it helped."

Someone will say placebo, someone will say random. For me (I don't mean in my opinion, but on myself) it works, as it did for two other people I gave it to and they saw improvements.

Note that as far as I know, a deficiency in B1 cannot be detected through blood tests. It requires a special examination. For me, it was easier to get a bottle and see what happens. And I saw...