Does Boiling Reishi Mushroom in Water Pose Any Health Risks?

Reishi mushroom (Ganoderma lucidum) has been used for centuries in traditional East Asian medicine, often prepared as a decoction by boiling the dried fungus in water. While generally considered safe for most healthy adults when consumed in moderation, reishi tea or decoctions are not without potential risks.

One of the primary concerns involves its anticoagulant properties—reishi contains triterpenes and polysaccharides that may inhibit platelet aggregation and interfere with thrombin activity. This poses a clinically significant risk for individuals taking anticoagulants (e.g., warfarin, apixaban) or antiplatelet agents (e.g., aspirin, clopidogrel), potentially increasing the risk of bruising, prolonged bleeding, or hemorrhage.

Hepatotoxicity is another documented concern. Although rare, several case reports have linked long-term or high-dose reishi supplementation—including decoctions—to elevated liver enzymes, hepatitis-like symptoms, and, in isolated instances, acute liver injury requiring hospitalization. Patients with preexisting liver disease or those concurrently using hepatotoxic medications should exercise caution.

Gastrointestinal intolerance is relatively common: nausea, dry mouth, pruritus, and diarrhea have been reported, particularly with prolonged use or concentrated preparations. Additionally, reishi may modulate immune function—potentially exacerbating autoimmune conditions such as rheumatoid arthritis or lupus—and is therefore contraindicated in patients receiving immunosuppressive therapy or organ transplant recipients.

Due to limited clinical trial data on standardized dosing and long-term safety, regulatory agencies like the U.S. FDA do not approve reishi for disease treatment. Consumers should consult a qualified healthcare provider before initiating regular use—especially those who are pregnant or lactating, have bleeding disorders, or are scheduled for surgery within two weeks.