@ristu I had been taking 2500 mcg that dissolve quickly in the mouth; Nature's Bounty is the one I use right now. Other brands have been fine as long as they dissolve before swallowing. My blood work shows that I "have too much Vit. B 12" but I'm unwilling to go off it! I've lately been taking one of these every other day and follow that same dosage with Liquid Vit. D....5 drops = 25 mcg. Just started taking Vit B Complex along with these two since I'm sure it's better to have a balance of B Vit.