Quick Summary
What did CL's tests of reishi supplements show?
We tested seven popular reishi supplements. Two were NOT APPROVED because they contained less than the expected 1,3:1,6-beta-D-glucan – a biologically active compound. Among five that were APPROVED, three were low in triterpene compounds known as ganoderic (and ganoderenic) acids, which may also play a role in the activity of reishi but are reduced in some extracts. None of the products tested for heavy metals failed those tests (see What CL Found and How Products Were Evaluated). 
Which reishi supplement is best?
Among five products APPROVED in testing, only one was found to provide reishi mushroom (not mycelium) with a large amount of beta-glucan and the highest level of triterpene compounds. That product is our Top Pick for reishi mushroom.
Reishi supplements tested include BulkSupplements.com Reishi Mushroom Extract, Freshcap Reishi, Host Defense Mushrooms Reishi, Life Extension Reishi Extract Mushroom Complex, Real Mushrooms Reishi, Swanson Reishi Mushroom Extract, and Om Reishi Mushroom Powder.
How to choose a reishi product?
When choosing a reishi product, make sure that the Supplement Facts panel lists reishi “mushroom” or “fruiting body” as the first ingredient, as this is what provides 1,3:1,6-beta-D-glucan. Products that, instead, list “mycelial biomass” as their first or only ingredient may simply contain large amounts of alpha-glucan, a common polysaccharide in grains, because reishi is grown on grains (such as oats or rice). Also know that, depending on how they are made, some reishi mushroom extracts contain very little of the triterpene compounds that are naturally in reishi (see What to Consider When Buying).
What is reishi?
Reishi (Ganoderma lucidum) is an edible mushroom. Reishi supplements, commonly sold as capsules or powders, contain material from the dried fruiting body (the top or "mushroom") with or without material from mycelia (the branch-like network that gives rise to the fruiting body). Extracts are also available in which certain compounds are more concentrated than in dried reishi, but others may be reduced (see What It Is).
Health benefits of reishi
Reishi supplements made from the fruiting body are commonly promoted for "strengthening" the immune system, lowering blood sugar, improving cardiovascular function, protecting against liver damage, and reducing cancerous tumors. However, the evidence supporting these effects is based on small, short-term studies. More research is needed to confirm these effects (see What It Does).
How to use reishi?
It's not clear whether reishi supplements are best taken with or without food, though limited evidence suggests that food may inhibit the absorption of certain triterpenes (see What to Consider When Using).
Reishi safety and side effects
Mild side effects may occur. High doses may have a blood-thinning effect (see Concerns and Cautions).
