There are a variety of factors you should take into account when choosing a Reishi supplement.
First is how you want to take it. As a supplement, you’ll find Reishi in powdered form or in capsules. The former is more concentrated, but the latter is more convenient, so this boils down to personal preference.
You should also look out for key words such as fruiting body and Certified Organic, since these are great indicators that you are getting the highest quality mushroom supplement.