I've suffered with insomnia since my early 20s (for about 10 years now) and my issues increased after a pretty severe motorcycle accident and resulting traumatic brain injury. I was up to like 40 milligrams of melatonin a night and it wasn't even necessarily working. I started talking Core-21 as recommended (5 days on, 2 off) and noticed a difference in my sleep quality after about a week of taking. I started sleeping more soundly and fell asleep more quickly. I still wake up in the night a few times but generally have an easier time falling back asleep when this happens. I don't always take it with the recommended 16-20 ounces of water since I already drink a ton of water and don't want to interrupt sleep for bathroom breaks if possible. Will definitely continue to purchase - I'm on bottle #2 right now.