Ive been suffering from terrible headaches for more than twenty years. I got some relief from taking Citracal, but later I discovered that Citracal has a lot of undesirable fillers, and not always the best form of calcium and magnesium. So I started taking Magnesium and Vitamin D/K from Pure Encapsulations. I knew it was a much cleaner supplement, and I did sleep better, but I still had frequent, debilitating headaches. Finally, I ordered this calcium and strangely enough, the calcium was the secret sauce that made it all work. I take all three before going to bed (calcium, magnesium, Vitamin d/k), and now my headaches are infrequent and mild. I hope this review will help someone else who suffers from headaches!