Quick answer

We found no trial of chaga on its own in people, so no benefit has been shown; the research on its effects is laboratory and animal work. Chaga is very high in oxalate. Powders tested in one report held 2.8 to 14.2 g per 100 g, and kidney damage has been reported after months of daily powder.^1,2,3

Key facts

A typical diet supplies 200 to 300 mg of oxalate a day, while 3 g of one chaga powder supplied about 420 mg.¹
In the three published kidney cases, people took chaga powder daily for 3 months to 5 years.^1,2,3
Chaga lives as a parasite on birch and other trees.³
In March 2026 the FDA warned a company that had marketed its chaga extract with research on illness.⁴

What chaga is

Chaga (Inonotus obliquus) is a fungus that lives as a parasite on birch and other trees.³

Chaga is sold as a ground powder, and every published case of kidney damage involved chaga powder taken daily.^1,2,3

Water and alcohol extracts of chaga from Finland, Russia and Thailand all contained oxalic acid as their main organic acid, the most in a Russian water extract.⁵

Chaga is sold as a ground powder and as water or alcohol extracts. Brewing chaga as a tea makes a water extract, so tea is likely to contain oxalate too, though none of the studies we found measured it.^1,5

What the evidence shows

No benefit claim for chaga passes our evidence rules. We searched PubMed for trials of chaga in people and found none that tested chaga on its own. The only human studies we found tested an herb mixture that was one fifth chaga, or blood cells in a dish.^6,7

The chaga studies that sellers cite are often laboratory work; the examples in the FDA's 2026 letter were studies of cells in a dish. Results in cells or mice do not show what a capsule or a cup of tea does in a person, and none has been confirmed in a human trial.^4,5

We also found no study in people of chaga for skin, or of its effects in men in particular.

What chaga's chemistry does show clearly is oxalate. Oxalic acid is the main organic acid in its extracts, and that is the source of its best-documented risk.^1,5

How much oxalate is in chaga

Chaga powders from three companies held 2.8 g, 11.2 g and 14.2 g of oxalate per 100 g.¹

At 0.14 g of oxalate per gram of powder, 3 g of chaga a day supplies about 420 mg of oxalate, and 9 g about 1,260 mg.¹

A typical diet supplies 200 to 300 mg of oxalate a day.¹

Oxalate binds calcium. When the kidneys have to clear too much of it, calcium oxalate crystals can settle in the kidney's tiny tubules and injure the cells lining them, which doctors call oxalate nephropathy.¹

Because oxalate varied about fivefold between the powders tested, the same spoonful can carry very different amounts. The dosage guide works out the oxalate in common daily amounts.¹

What's in ours

Chaga is one of six mushrooms in our Mushroom Complex's proprietary blend. The label gives the blend's total, shown above, but not the chaga share, and no safe amount of chaga has been established.

Kidney reports, other cautions and who should not take it

Oxalate nephropathy, kidney damage from oxalate crystals, has been reported in at least three people who took chaga powder every day for months or years.^1,2,3

A 49-year-old man who took 3 g of chaga powder a day for four years, then 9 g a day for a year, developed kidney failure and was still on dialysis 18 months later.¹

A 69-year-old man who took 10 to 15 g of chaga powder a day, with 500 mg of vitamin C, for three months developed acute kidney injury. His kidneys recovered after dialysis and steroid treatment.³

A 72-year-old woman under treatment for liver cancer took 4 to 5 teaspoons of chaga powder a day for six months and needed dialysis for oxalate kidney damage.²

No upper limit or safe daily amount has been set for chaga. In the reports that gave amounts in grams, people with kidney damage took 3 to 15 g of powder a day, for 3 months to 5 years.^1,3

Lab and animal studies raise two more questions. A peptide from chaga slowed platelet clumping in the lab and in mice, and chaga polysaccharides lowered blood sugar in mice. Neither has been tested in people, but ask first if you take a blood thinner or a medicine that lowers blood sugar.^8,9

Do not take chaga if you have kidney disease or have had kidney stones, unless your kidney doctor agrees¹
Ask first if you take vitamin C supplements, another source of oxalate^1,3
Ask first if you take a blood thinner, insulin or another medicine that lowers blood sugar^8,9
Ask first if you are pregnant or breastfeeding, or under cancer care
If you have taken chaga daily for months, tell your doctor, who may want to check your kidney function¹

Be wary of sellers who say chaga treats cancer or viruses. Supplements may not be sold with such claims, and in 2026 the FDA warned a company that made them.⁴

Questions people ask

What does chaga do for the body?

In people, nothing has been shown. Its compounds have been tested in cells and animals, but we found no trial of chaga on its own in humans, so its effects in people are unknown.^5,9

Does chaga have benefits for skin?

We found no study in people. In one published case, a man took chaga powder for five years for a skin condition, atopic dermatitis, and developed kidney failure from oxalate.¹

Where does chaga come from?

Chaga grows as a parasite on birch and other trees. The extracts analyzed in one study came from Finland, Russia and Thailand, and their oxalic acid content differed by origin, with the most in a Russian water extract.^3,5

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.