I started taking B12 after watching a video Jay from Plant Based Athlete did about a year ago, in which he was discussing some of the benefits of B12. From the first day I started taking it, the benefits I experienced from B12 were immediate, including curing me of my chronic insomnia that I've suffered with for the last 15 years. Every night of sleep is now better than the next. And mind you, my B12 levels never looked low on my blood test results. I just thought I'd try it on a whim after hearing his advice, and I feel amazing. I'm so grateful I decided to tried it. I take a brand called Jarrow, which I buy at Sprouts Farmer Market. It's 5000 mcg/tablet, Methylcobalamin. I also read there's a huge difference between swallowing whole and dissolving the tablet slowly in your mouth. When you take it in lozenge form and allow it to dissolve in your mouth naturally, it has much better absorption in the body, than swallowing it whole.