Quick Answer
Reishi (Ganoderma lucidum, also sold as lingzhi or red reishi) is a woody, bitter functional mushroom studied mainly for how it affects the immune system. The best-designed human trial so far found changes in immune cell counts after 12 weeks of a reishi supplement. Research on sleep and stress is earlier and less certain. Because the mushroom is too tough to eat, most people take a reishi mushroom supplement as a tincture, extract powder or capsule. Before you buy, check two things: whether the product uses the fruiting body, and how it was extracted.
What Is Reishi?
Reishi is a polypore, a shelf-like mushroom that grows on hardwood. The fruiting body is glossy, reddish-brown and hard, so it is usually sliced and simmered or extracted rather than cooked. It has a long history of traditional use in East Asia, but tradition is not evidence, so this guide focuses on modern studies. For the wider picture, our functional mushroom benefits guide compares reishi with lion’s mane, cordyceps and turkey tail.
What the Research Says
Immune response
The strongest reishi study we know of is a 2023 randomised, double-blind, placebo-controlled trial published in Foods. 135 healthy adults aged 18 to 55 completed 12 weeks of either a reishi beta-glucan supplement or a placebo. The reishi group showed higher counts of several immune cells, including T cells and natural killer cells, and higher levels of the antibody IgA, with no significant change in liver or kidney markers.
That is a measurable change in immune markers in healthy people. It does not show that reishi prevents or treats illness.
Sleep and stress
Reishi is often described as calming and is popular as an evening supplement. The evidence here is much thinner, coming mostly from animal studies and small human trials, so treat sleep and stress benefits as possible rather than proven. Our functional mushroom research update tracks newer studies as they are published.
Reishi Forms Compared
| Form | What it is | Good for | Watch out for |
|---|---|---|---|
| Dual-extract tincture | Alcohol and water extraction in a dropper bottle | Daily use, easy to add to drinks | Contains alcohol; check the extraction method is stated |
| Extract powder | Concentrated, dried extract | Mixing into coffee or smoothies | Very bitter taste |
| Whole ground powder | Dried mushroom, milled but not extracted | Lower cost | Several published liver case reports involve powders |
| Capsules | Powder or extract in a capsule | Fixed amounts, no taste | Check what is actually inside |
| Tea | Slices simmered in water | Traditional use | Water mainly draws out beta-glucans, not triterpenes |
How to Choose a Reishi Supplement
Fruiting body or mycelium. Some supplements are made from mycelium grown on grain rather than from the mushroom itself, and the finished product can contain a lot of grain starch. A good label says which part of the fungus is used.
Extraction method. Reishi’s two most studied compound groups dissolve differently. Beta-glucans come out in hot water, while triterpenes need alcohol. A dual extraction uses both, which is why it is the most common format for tinctures. Our dual-extracted red reishi tincture uses both alcohol and water extraction and comes in a 50ml dropper bottle.
What the label should tell you. Look for the Latin species name, the part used, the extraction method and, if a beta-glucan figure is given, how it was measured. Be wary of any label or listing that promises to cure or prevent a condition.
How to Take Reishi and How Long It Takes
Many people take reishi in the evening, though no research shows one time of day works better. Consistency matters more. The 2023 trial measured its results after 12 weeks, so don’t expect to notice anything within days. For amounts used in studies and by format, see our functional mushroom dosage guide, and always follow the label on the product you buy.
Side Effects and Who Should Avoid It
Mild side effects such as nausea or dry mouth have occasionally been reported, according to a review of reishi studies. There are rare published case reports of liver injury in people taking reishi powder, including a 2023 case where alcohol may also have played a part and an earlier fatal case after a switch to a powdered form. The cause is not always clear, but stop taking reishi and seek medical advice if you notice yellowing skin or eyes, dark urine or unusual tiredness.
Speak to a GP or pharmacist before taking reishi if you take blood-thinning or blood pressure medication, have surgery planned, have a liver condition, or are pregnant or breastfeeding.
Prefer to Grow Your Own?
Our reishi cultivation guide covers indoor blocks and outdoor logs, and our shiitake and reishi growing kits guide explains what to expect from a kit.
Common Mistakes
- Not checking which part is used. A product made from mycelium on grain is a different thing from a fruiting body extract.
- Expecting quick results. The best trial ran for 12 weeks.
- Choosing the wrong extraction. A water-only product will contain few triterpenes.
- Ignoring medication. Check with a pharmacist first if you take regular medicines.
FAQ
How long does reishi take to work?
The best-designed trial measured changes in immune markers after 12 weeks of daily use. Most people should think in weeks rather than days, and some may notice no change at all.
When is the best time to take reishi?
No research shows that one time of day is better. Many people take it in the evening as part of a routine, and taking it consistently matters more than timing.
Does reishi make you sleepy?
Some people describe reishi as calming, but it is not proven to cause drowsiness or to work as a sleep aid.
Reishi or lion’s mane: which should I take?
They are studied for different things: reishi mainly for the immune system, lion’s mane mainly for focus and memory. Our which functional mushroom guide compares them side by side.
Can you eat reishi like other mushrooms?
Not really. Reishi is too woody and bitter to cook like a culinary mushroom, so it is usually simmered as a tea or taken as an extract.
Can I take reishi every day?
The 2023 trial used daily intake for 12 weeks without significant changes in liver or kidney markers. Follow the label, and speak to a GP if you have a health condition or plan to take it long term.
Why This Matters
Reishi products vary widely. Knowing the difference between fruiting body and mycelium, and between water and dual extraction, is the simplest way to buy a product that matches the research.
Related Guides
- Functional mushroom benefits guide
- Functional mushroom dosage guide
- Functional mushroom stack guide
- Chaga mushroom UK buying guide
- Reishi cultivation at home
About This Guide
This guide was written by the SporeBuddies team and summarises published research available in October 2026. It is general information, not medical advice. Speak to a GP or pharmacist before starting any supplement if you have a health condition or take medication.
Ready to try reishi? Browse our 50ml mushroom tincture extracts and choose the Red Reishi option.