Reishi, chaga and cordyceps: which one actually shows up on a blood test

Why are people suddenly asking about this?

Because the category grew faster than the evidence did. Which? reviewed functional mushrooms on 26 November 2025 and was blunt about what the research shows:

“Unfortunately, there isn't good evidence supporting any solid health claims for most of the popular ‘functional’ mushrooms.”

Which?, November 2025

The same review notes there are no approved health claims for mushrooms on the Great Britain Nutrition and Health Claims Register. So nobody in the UK is allowed to tell you a mushroom capsule treats anything.

Safety is the more interesting half. Most people take these powders without any trouble at all. But two of the three big sellers have a documented signal in the medical literature, and they point at different organs. Lumping them together is the mistake most articles make.

Reishi and your liver

Reishi is the one to watch. It is sold as reishi, as Ganoderma lucidum, and as lingzhi. All three names mean the same mushroom.

LiverTox, the US National Institutes of Health database that catalogues supplement-related liver injury, lists reishi as a possible rare cause. It gives the entry a likelihood score of D, which is its rating for a possible rare cause rather than a proven common one. In small placebo-controlled trials, liver enzymes did not shift at all.

Two details from that entry matter if you are going to test. The injury is hepatocellular, meaning it hits the liver cells themselves. And the latency is typically one to two months, with a reported range from a few days to six months. That timing is the whole reason a single test before you start tells you nothing.

ALT is the marker that catches it. ALT is an enzyme that normally lives inside liver cells. When those cells are under strain it leaks out into the blood, so the number climbs before you feel anything is wrong. ALP is the second liver marker, and it is read alongside ALT to show whether the problem sits in the cells or in the bile drainage.

The numbers in the case reports are not subtle. A 2023 case in Cureus describes someone who took lingzhi powder while also drinking. Their ALT was 990 U/L on admission and their AST was 301 U/L. The authors point out that the ratio between the two did not look like alcohol damage, which is what pointed them at the supplement. The same paper cites an earlier fatal case of fulminant hepatitis in a patient who switched from traditionally boiled lingzhi to the powder.

Read that carefully. It is rare. The published reports number in the handful, mostly from China, Japan, Thailand and India. But alcohol appears in more than one of them, and so does the concentrated powder or extract rather than the traditional brew. Helvy does not sell mushroom supplements. Our guide on high ALT levels explains what a raised reading does and does not mean.

Chaga and your kidneys

Chaga is the one people get wrong. Its documented problem is not the liver at all. It is the kidney.

Chaga is very high in oxalate. Oxalate is a natural plant acid that binds to calcium and can form sharp crystals. Take enough of it and those crystals can lodge in the filtering tubes of the kidney. The medical name is oxalate nephropathy.

A 2022 case report in Medicine follows a 69-year-old man taking 10 to 15 grams of chaga powder a day alongside 500 mg of vitamin C. He did this for three months. His creatinine reached 6.94 mg/dL and his eGFR fell to 7.9. He needed emergency dialysis. After a month of treatment his creatinine was back to 1.00 mg/dL.

Creatinine and eGFR are the markers here. Creatinine is a waste product your muscles make all day, and healthy kidneys clear it steadily. If it builds up in the blood, the filtering is not keeping pace. eGFR is that same number turned into an estimate of how fast your kidneys are filtering. Urea is read alongside both.

The vitamin C in that case is not a footnote. Your body converts some vitamin C into oxalate, so a high-dose vitamin C habit stacks on top of a high-oxalate powder. Two teaspoons of chaga is a very different exposure to ten grams a day, and dose is doing most of the work in every published case.

Cordyceps, the quiet one

Cordyceps gets swept into the same warnings, and on the current evidence that is not fair. LiverTox records no published reports of raised liver enzymes or clinically apparent liver injury attributed to cordyceps extracts, despite widespread use.

That is worth saying plainly, and it is worth not over-reading. No reported cases is not the same as proven safe for everyone. It means nobody has published a signal. If you are taking cordyceps on its own, the liver argument for testing is weak. If it is one tub in a stack of five, you are not really testing cordyceps.

What to check, and when

The British Society of Gastroenterology already treats supplements as a live suspect. Its guidelines on abnormal liver blood tests tell clinicians to take a drug history covering what was “prescribed, over the counter, herbal, injecting drug use, illicit”. When the wider workup comes back clear, they go further:

“it is important to re-examine the history to exclude potential drug-induced aetiologies, including over-the-counter preparations and any potential recreational/herbal drug use.”

Newsome PN, et al. Gut 2018;67:6-19

That is the clinical version of the same point. Your supplement shelf is part of your history. The practical shape follows from the reishi latency:

• Get a baseline before you start. A number with nothing to compare it to is close to useless.
• Recheck at about eight weeks. That sits inside the one to two month window the case reports keep describing.
• Start one thing at a time. Four new tubs in one week and a changed result has no clear owner.
• Count your dose honestly. Every published chaga case involved grams a day for months, not a spoon in a coffee.

The markers are ALT and ALP for the liver, and urea, creatinine and eGFR for the kidneys. All five sit together on Helvy's Thyroid & Vital Organs panel at £159, from a home finger-prick sample. One caveat worth knowing: GGT and bilirubin are part of a standard NHS liver panel and are not on ours. If a clinician wants those, that is a GP conversation.

Do not wait for a test if you feel unwell. Stop the capsules and see a doctor promptly if you notice yellowing of the skin or eyes, dark urine, pale stools, itching, or pain under the right ribs. The NHS lists these as signs of a liver under strain. Suspected reactions can be reported through the MHRA Yellow Card scheme.

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