Reishi mushroom contains compounds that can influence blood pressure, but the human evidence is mixed and generally weak. The most rigorous review of clinical trials, published in the Cochrane Library, found no statistically significant differences in blood pressure between people taking reishi and those taking a placebo. That said, a small number of trials have reported meaningful reductions, particularly in people with more severe high blood pressure, so the picture isn’t entirely negative.
What the Clinical Evidence Shows
The strongest summary of the research comes from a Cochrane systematic review that pooled data from randomized controlled trials of reishi in people with type 2 diabetes and cardiovascular risk factors. The conclusion was blunt: reishi was not an effective treatment for reducing blood pressure, blood glucose, or cholesterol. The review also noted that the trials it analyzed were small and few in number, which limits confidence in any direction.
Outside that review, the evidence is inconsistent. One trial using a concentrated 25:1 reishi extract (55 mg taken three times daily for four weeks) did report significant blood pressure reductions compared to controls. Another controlled trial found similar results. But a separate study found that taking reishi extract daily for 12 weeks did not lower blood pressure in people with mildly elevated readings. The pattern that emerges is that reishi may have a modest effect in people whose blood pressure is already significantly high, while doing little for those with borderline numbers.
How Reishi Could Affect Blood Pressure
Lab research has identified several plausible ways reishi might influence blood pressure, even if clinical trials haven’t consistently confirmed those effects in humans. Five specific compounds isolated from reishi (including ganoderic acids K and S, ganoderal A, and ganoderols A and B) have been shown to inhibit angiotensin-converting enzyme, the same enzyme targeted by common blood pressure medications like lisinopril and enalapril. When this enzyme is blocked, blood vessels relax and widen, which lowers pressure.
A separate line of research, conducted in diabetic rats, found that polysaccharides from a related Ganoderma species improved the ability of blood vessels to relax by boosting nitric oxide production. Nitric oxide is a signaling molecule that tells blood vessel walls to loosen up. In the study, diabetic rats treated with the polysaccharide had significantly better blood vessel relaxation than untreated diabetic rats. This is relevant because impaired blood vessel function is a major contributor to high blood pressure in people with diabetes. However, this research used a related species (Ganoderma atrum, not the standard reishi Ganoderma lucidum), and animal results don’t always translate to humans.
Interactions With Blood Pressure Medications
Even though the evidence for reishi lowering blood pressure on its own is weak, the interaction risk with blood pressure medications is real. The Merck Manual specifically warns that combining reishi with common antihypertensives, including ACE inhibitors (captopril, enalapril, lisinopril), calcium channel blockers (amlodipine), and diuretics (hydrochlorothiazide), could cause blood pressure to drop too low. The MSD Manual similarly flags the potential for reishi to produce hypotension when taken alongside these drugs.
This is worth paying attention to even if you think reishi’s blood pressure effects are mild. A small additional drop on top of medication could be enough to cause dizziness, lightheadedness, or fainting, especially when standing up quickly. If you’re already on blood pressure medication, this is a combination to discuss with whoever prescribes it.
Dosage and Timeline
The trial that reported positive results used a highly concentrated extract (25:1 ratio, meaning 25 pounds of mushroom reduced to 1 pound of extract) at 55 mg three times daily for four weeks. That’s a very different product from the dried reishi powder capsules sold in most supplement aisles, which typically contain 1,000 to 3,000 mg of non-concentrated material. Extract concentration and preparation method vary wildly between products, making it difficult to compare what you’d buy off a shelf to what was tested in a study.
The timeline also varies. The positive trial saw effects within four weeks, while a 12-week trial in people with mildly elevated blood pressure saw no benefit at all. This suggests that the type of extract, the severity of existing blood pressure problems, and individual biology all play a role in whether reishi does anything measurable.
The Bottom Line on Reishi and Blood Pressure
Reishi contains compounds with real biological activity against the systems that regulate blood pressure. But when tested in humans under controlled conditions, the results have been inconsistent and mostly unimpressive. The Cochrane review, which represents the highest standard of evidence evaluation, found no support for using reishi to manage cardiovascular risk factors. A couple of smaller trials showed modest effects in people with higher baseline blood pressure, but these studies were limited in size and quality. Reishi is not a reliable substitute for proven blood pressure treatments, though it does carry a real risk of interacting with medications that lower blood pressure.