Quick answer
Reishi's ganoderic acids reach the blood within 5 to 10 minutes and peak at about 30 minutes, but that is not an effect you can feel. Trials in healthy adults measured changes after 10 days to 12 weeks, and only a purified beta-glucan extract changed immune cell counts, at the 12-week check.1,2,3
Key facts
- Taken fasting, ganoderic acid levels halved in under 40 minutes after peaking.1
- After breakfast, the peak of ganoderic acid A came later and lower.1
- Plasma antioxidant capacity peaked about 90 minutes after a single 1.1 g dose.4
- The beta-glucan trial took blood only at the start and after 12 weeks, so it cannot show when changes began.3
How fast reishi reaches the blood
Taken on an empty stomach, ganoderic acids from a 3 g dose of reishi extract appeared in the blood within 5 to 10 minutes and peaked at about 30 minutes. Their levels then halved in under 40 minutes.1
Taken straight after breakfast, the same dose gave a lower, later peak of ganoderic acid A with the same total absorbed, but ganoderic acid F stayed too low to measure in most of the 12 men.1
Only a small share of the ganoderic acids swallowed reached the blood, even from a large dose. The authors suggested that the liver and gut bacteria break much of it down before it circulates.1
The study measured just two ganoderic acids, for eight hours after one dose. Reishi's beta-glucans and other compounds were not tracked, so how quickly they act, if they act at all, is unknown.1
What changed over days and weeks
Each trial gave reishi every day for a set period and compared blood tests from before and after. Here is how long each ran and what it found.
| Trial | Daily amount | Length | What it found |
|---|---|---|---|
| Extract trial, 16 people | 4 g | 10 days | No clear change in immune cell counts |
| Biomarker trial, 18 people | 1.44 g | 4 weeks | No blood marker changed; urine antioxidant capacity rose |
| Clotting trial, 40 people | 1.5 g | 4 weeks | Clotting and platelet tests unchanged |
| Beta-glucan trial, 157 people | 200 mg of purified extract | 12 weeks | See the graded finding below |
A purified reishi beta-glucan may raise counts of some immune cells in healthy adults*2,3,5,7
Early evidence
In a randomized, placebo-controlled trial in healthy adults aged 18 to 55 (157 enrolled, 135 finished), 200 mg a day of a purified reishi beta-glucan for 12 weeks raised counts of several kinds of T cells and natural killer cells more than placebo. It did not measure whether people fell ill less often, and a company paid for it. A trial in young children who ate a yogurt with reishi beta-glucans found a similar rise. Whole reishi did not show this: 1.44 g a day for 4 weeks, and 4 g a day of an extract for 10 days, left immune measures unchanged in small trials.
Amount studied: 200 mg a day of purified reishi beta-glucan, for 12 weeks
Because that trial checked blood only twice, it cannot say whether the change appeared after two weeks or only near the end. We found no trial in healthy adults that looked for an effect a person could notice.3
What happens when you stop
In a 10-day trial of 4 g a day, natural killer cell counts drifted up during use and were back at their starting level 10 days after stopping. The rise was not statistically significant.2
We found no study that followed healthy adults for months after they stopped reishi, so how long any change lasts is not known.
When to watch for side effects
Side effects can take time to show as well. In the rare liver cases LiverTox describes, trouble usually began 1 to 2 months after starting reishi, though the range ran from a few days to six months. Recovery after stopping usually took 1 to 3 months.8
Watch for dark urine, yellowing skin or eyes, or unusual tiredness, especially in the first few months, and stop reishi if they appear.8
Questions people ask
How long does reishi stay in your system?
In the absorption study we read, ganoderic acid levels halved in under 40 minutes after peaking, and blood was sampled for 8 hours. The study did not measure reishi's other compounds, such as beta-glucans.1
Should I take reishi with food?
There is no evidence that it changes any effect. In the absorption study, breakfast lowered and delayed the peak of one ganoderic acid without changing the total absorbed, but left another mostly too low to measure.1
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Sources
- Teekachunhatean S, Sadja S, Ampasavate C, Chiranthanut N, Rojanasthien N, Sangdee C. Pharmacokinetics of ganoderic acids A and F after oral administration of Ling Zhi preparation in healthy male volunteers. Evid Based Complement Alternat Med. 2012;2012:780892. Opened 2026-10-07.
- Wicks SM, Tong R, Wang CZ, O'Connor M, Karrison T, Li S, Moss J, Yuan CS. Safety and tolerability of Ganoderma lucidum in healthy subjects: a double-blind randomized placebo-controlled trial. Am J Chin Med. 2007;35(3):407-414. Opened 2026-10-07.
- Chen SN, Nan FH, Liu MW, Yang MF, Chang YC, Chen S. Evaluation of Immune Modulation by β-1,3; 1,6 D-Glucan Derived from Ganoderma lucidum in Healthy Adult Volunteers, A Randomized Controlled Trial. Foods. 2023;12(3):659. Opened 2026-10-07.
- Wachtel-Galor S, Szeto YT, Tomlinson B, Benzie IF. Ganoderma lucidum ('Lingzhi'); acute and short-term biomarker response to supplementation. Int J Food Sci Nutr. 2004;55(1):75-83. Opened 2026-10-07.
- Wachtel-Galor S, Tomlinson B, Benzie IF. Ganoderma lucidum ("Lingzhi"), a Chinese medicinal mushroom: biomarker responses in a controlled human supplementation study. Br J Nutr. 2004;91(2):263-269. Opened 2026-10-07.
- Kwok Y, Ng KFJ, Li CCF, Lam CCK, Man RYK. A prospective, randomized, double-blind, placebo-controlled study of the platelet and global hemostatic effects of Ganoderma lucidum (Ling-Zhi) in healthy volunteers. Anesth Analg. 2005;101(2):423-426. Opened 2026-10-07.
- Henao SLD, Urrego SA, Cano AM, Higuita EA. Randomized Clinical Trial for the Evaluation of Immune Modulation by Yogurt Enriched with β-Glucans from Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum (Agaricomycetes), in Children from Medellin, Colombia. Int J Med Mushrooms. 2018;20(8):705-716. Opened 2026-10-07.
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Lingzhi, Reishi. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases. Last update October 5, 2024. Opened 2026-10-07.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.