Here's a little info: It's based on Dr St Amand's theory that all our FMS/CFSsymptoms are caused by our bodies being genetically unable to rid themselves of phosphates. It is essential to read & exactly follow Dr Paul St Amand's book 'What your doctor may not tell you about fibromyalgia'. ( Confusingly, he also has a book with the same title but the word 'fatigue' on the end. This has the basic info but has more about his diet for those of us who are hypoglycemic.) Not all Guaifenesin will work consistently; you need to buy a recommended brand,several of which are sold here (go to 'store' at the top of the page). It takes a lot of determination.This is a treatment for life, not a cure. It supposedly reverses the symptoms of FMS/CFS (& the associated brainfog, IC, IBS, skin conditions etc. etc.).As you reverse cycle, you will feel worse. In fact, your correct dosage is one that makes you feel tolerably worse. Salicylates will stop the Guai from working, which is one reason you need the book. You cannot e.g. take asprin, use mint dental products, use toiletries with plant extracts,garden without gloves etc. etc. You don't need a doctor to do this. There are Guai Group message boards for both the US & UK. They have lists of sal free products. Dr St Amand has a Guaidoc website. Hope this helps a little.