It's supposed to increase "brain oxygenation" / blood flow, but in some individuals who already have good blood flow it may cause bleeding. It feels like your brain is melting, quite peculiar and alarming. Can also happen in conjunction with e.g. ibuprofen or aspirin.
"Herbal" doesn't mean "safe". Many are toxic.
Also, you may be allergic to or sensitive to a particular plant component which is innocuous to other people who recommend it. When trying out ANY new supplement, try only a very small amount at first, to see how you react to it. Then slowly increase the dosage. First priority is NOT going for effect, but seeing if something will hurt you before you try to imbibe enough to gain some positive effect.
Note that capsules typically contain quite a high dosage, because they are trying to appeal to regular users by packing the most mg per dollar. Never assume that ONE cap is "LOW". Research the low end of the dosage scale, and then have EVEN LESS. E.g. if substance X is sold in caps from 10mg to 100mg, get a 10, and then OPEN THE CAP and have a small amount, NOT the whole cap.
Even something as innocuous as melatonin can be a real drag; it's often sold in 3mg pills, when 0.3mg is effective, and for many people it has a delayed effect where it doesn't help you sleep that night but kicks in the next day and you can barely function because your body thinks it's time to sleep!
First priority is always to protect yourself and limit the side-effects if something doesn't agree with you.
Piracetam worked much better for me. However, nothing has worked better for me than a decent diet and making sure to drink enough water a day (and getting the appropriate amount of sleep).
The most important for me is decent sleep = 7+-1 hours; wake up at 8, no later.
