How do I know if I take too many Reishi Mushrooms (Ganoderma lucidum)?

Side effects of taking high doses of Reishi mushroom may include itching, nausea, stomach upset, rash etc. Most side effects of Reishi aren't fatal. The right dosage of Reishi depends on the form you are taking. You can take more than 25grams daily when you consume the mushroom itself, while anything more than 9grams daily of the dry mushroom extract may be considered an overdose.