A variety of dietary supplements and herbal preparations are claimed to have potential benefits for CFS patients. With few exceptions, the effectiveness of these remedies for treating CFS has not been evaluated in controlled trials. Contrary to common belief, the "natural" origin of a product does not ensure safety. Dietary supplements and herbal preparations can have potentially serious side reactions and some can interfere or interact with prescription medications. CFS patients should seek the advice of their health care provider before using any unprescribed remedy.

Herbal preparations: Plants are known sources of many pharmacological materials. However, unrefined plant preparations contain variable levels of the active compound and may contain many irrelevant, potentially harmful substances. Preparations that have been claimed to have benefit to CFS patients include astralagus, borage seed oil, bromelain, comfrey, echinacea, garlic, Ginkgo biloba, ginseng, primrose oil, quercetin, St. John's wort, and Shiitake mushroom extract. Only primrose oil was evaluated in a controlled study, and the beneficial effects noted in CFS patients have not been independently confirmed. Some herbal preparations, notably comfrey and high-dose ginseng, have recognized harmful effects.