Urolithin B dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
Urolithin B is sold on the good name of urolithin A, which has human studies. Urolithin B has none. Its muscle result comes from muscle cells in a dish and from mice given 10 micrograms a day through a pump placed under the skin for 28 days.
Evidence grade for Urolithin B: Limited. The rule: people have taken it in a published study, but fewer than 100 of them. The sum on this page: 1 completed trial, none stating how many people. A grade counts how much has been done to people, not whether it works.
- People given it
- 0
- Human studies
- 1
- Found nothing
- 1
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
1 completed trial, 0 people given it
No first-hand reports gathered yet. That is a gap in what we have collected, not a finding that nothing has been reported.
Goal pages: Muscle and strength, Hormones and growth hormone
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
Urolithin B is made by gut bacteria from foods like pomegranate and walnuts. It is sold as a muscle supplement. It is often confused with urolithin A, which has human studies. Urolithin B has none.
What people take it for
- Building or keeping muscle.
- A cheaper stand-in for urolithin A.
What studies in people showed
No person has taken it in a study. In mouse muscle cells in a dish, it made the cells grow. In mice, a pump under the skin gave 10 micrograms a day for 28 days. Their muscles got bigger and wasted less after a nerve injury. A pill is not the same as a nonstop pump. Its cousin urolithin A has been tested in people, and even it missed some main goals.
What people report
Reports, not study results
The good
- We have not collected user reports on this one yet.
The bad
- There is no human safety data and no known dose for people.
Where these come from: The bad line is from the notes on this page. We have not collected user reports on this one yet.
My bottom line
No human data at all. Do not buy it on urolithin A's name. Protein and lifting are what build muscle.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Measured in people
Goals Urolithin B has been tested for in people, biggest studies first. We count only what the studies on this page say, so the real numbers may be higher.
- Getting strongerno headcount stated · 1 study · 1 found nothing
- Lasting longer, staminano headcount stated · 1 study · 1 found nothing
Animal and lab work, not yet tested in people
Real results, but from animals or cells, not people. What works in a mouse often does not work the same way in a person. Nobody can patent this, so nobody would ever earn back the cost of a study in people. That is usually why there is none. The record on this one is set out below.
- Keeping or building muscle1 animal or lab study
- Testosterone and male hormones1 animal or lab study
32 of the 36 indexed goals have no study of any kind behind Urolithin B
No study in people, animals or cells on this page reports a result for these. That does not prove Urolithin B does nothing for them. It does mean anything you have heard about Urolithin B and one of these did not come from a study cited here.
Show full evidence
What is Urolithin B?
Urolithin B is sold on the good name of urolithin A, which has human studies. Urolithin B has none. Its muscle result comes from muscle cells in a dish and from mice given 10 micrograms a day through a pump placed under the skin for 28 days.
Urolithin B is one of the compounds gut bacteria make from plant compounds, called ellagitannins, in pomegranate, walnuts and berries. It is simpler in structure than urolithin A and has a different claimed action. The 2017 paper that made its name did not say it clears out old mitochondria. It said it controls muscle protein balance by working through the androgen receptor, the receptor testosterone uses.
That paper is the whole case. In mouse muscle cells in a dish, urolithin B for 24 hours made the cells grow and mature more. It did this by raising protein building and turning down the system that breaks protein down. Gene and drug tests pointed to the androgen receptor, with some links to other growth signals. In mice, 10 micrograms a day, given nonstop for 28 days by a small pump placed under the skin, made muscles bigger and cut muscle wasting after a nerve was cut. A 2025 study in blood vessel muscle cells in a dish reports a separate effect that slowed their growth.
No person has been given urolithin B in a study. Not for muscle, not for anything. Shop copy mixes it up with urolithin A all the time, and that matters. Urolithin A is the one with a first safety study in people, a four-month study against a dummy in older adults, and one in middle-aged adults. Even those studies missed main goals. Urolithin B has none of that record and is often sold as if it shares it.
How does Urolithin B work?
In muscle cells and mice, it raised protein building and turned down the system that breaks protein down. Gene and drug tests point to the androgen receptor, with links to the mTORC1 growth signal, possibly through AMPK. That is a different claimed action from urolithin A, which is sold and studied for clearing out old mitochondria. Which urolithins a person makes from food depends on their gut bacteria. People fall into different types: some mainly make urolithin A, some urolithin B, and some other forms.
The state of the research
There is no human evidence section on this page because there is no human evidence. No registered study has given urolithin B to a person. The searches behind this page found nothing beyond lab digestion chemistry and studies that sort people by the urolithins their gut makes.
How it was given in the only live animal study deserves attention. The mice did not eat urolithin B. They had small pumps placed under the skin that released 10 micrograms a day, nonstop, for 28 days. That gives steady levels a once-a-day capsule does not match, in an animal whose muscle differs from ours anyway.
The sales context is why this page exists. Urolithin A reached human studies and is sold as a branded ingredient. Even there, the studies are honest about missing their main goals on peak muscle power and the six-minute walk. Urolithin B is cheaper, is a chemical neighbour, and is sold in the same category with the same words. The two molecules have different claimed actions, one through clearing old mitochondria and one through the androgen receptor. Only one has ever been given to a person in a study.
One more practical point. Which urolithins you make from pomegranate or walnuts depends on your gut bacteria, and people fall into different types. That is one reason researchers moved to giving specific urolithins directly. It is also a reason not to assume eating the food gives you any one of them.
The evidence, in charts
Fig. 1a · how many people
1study in people cited, but none says how many people took part
number of people not stated
We do not draw a total, because none of the studies in people on this page gives one. Read the sources below for what each study measured.
We read the number of people from the source lines on this page. Where a line gives no number, we count nothing for it. We do not guess.
Fig. 1b · evidence mix
1 of 4 sources here is a study in people. The rest are not.
- Study in people · done in people125%
- Animal study · done in animals125%
- Lab (cells in a dish) · cells or tissue250%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
The studies cover 3 different years, 2017 to 2025, counted from the list of sources on this page.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 4 · how much does what
Nobody has tested different amounts in people
This chart would show how the effect changes as the amount goes up. For this compound, nobody has measured that in people. So we leave it empty. We will not borrow an animal chart and pretend it works the same in people.
Fig. 5 · what the molecule is
- Kind of compound
- Supplement
- Molecule weight
- 212.2 Da
- Half-life
- Stated in words, not a numbersee the exact wording below
- Chain length
- None on file
Half-life as stated on file: Not established in humans. No human pharmacokinetic study of administered urolithin B exists.
No amino acid sequence is on file for Urolithin B, which is expected: a supplement is not built from amino acids.
The studies we cite
- Study in people2022Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial
This is urolithin A, not urolithin B, and it sits here because urolithin B has nothing like it. Older adults took urolithin A or a dummy. Muscle endurance improved and some blood markers moved. The six minute walk test did not improve, and neither did the peak energy output measured inside muscle. So even the better studied sibling comes out mixed. Urolithin B has never been tested this way, or in any other way, in a person.
Included as the contrast, and it is not urolithin B. This is a randomised trial of urolithin A in older adults, in which muscle endurance and plasma biomarkers improved while the six-minute walk and peak ATP did not differ from placebo. Urolithin B has no trial of this kind, or of any kind.
- Animal study2017Urolithin B, a newly identified regulator of skeletal muscle mass
In mouse muscle cells in a dish and in mice. Urolithin B made the cells grow, through more protein building and less protein breakdown, and the androgen receptor was involved. In mice, a nonstop dose from a pump under the skin for 28 days made muscles bigger and cut wasting after nerve injury. Not a dose by mouth, and not in people.
C2C12 myotubes treated with 15 micromolar urolithin B for 24 hours grew and differentiated more, through increased protein synthesis and repression of the ubiquitin-proteasome pathway, with the androgen receptor implicated. In mice, 10 micrograms a day delivered continuously by implanted mini-osmotic pump for 28 days induced muscle hypertrophy and reduced atrophy after sciatic nerve section. Cells and mice, by continuous infusion, not an oral human dose.
- Lab (cells in a dish)2025Urolithin B suppresses phenotypic switch in vascular smooth muscle cells induced by PDGF-BB via inhibiting the PI3K-AKT pathway
In a dish, using blood vessel muscle cells. Urolithin B slowed a change that makes these cells grow. It is a separate claimed effect, with no animal or human follow-up.
Vascular smooth muscle cells in culture. A separate proposed action, entirely in vitro, with no animal or human follow-up.
- Lab (cells in a dish)2017Gastrointestinal stability of urolithins: an in vitro approach
A lab test of how well urolithins survive digestion. It matters because the only live animal study used a pump under the skin, which skips the gut completely.
In vitro digestion work on the stability of urolithins through the gastrointestinal tract. Relevant because the only in vivo urolithin B data came from a pump implanted under the skin, which bypasses the gut entirely.
Common questions
Has Urolithin B been tested in people?
Yes. 0 people given it across 1 completed trial cited here, 1 of which found nothing. Urolithin B is sold on the good name of urolithin A, which has human studies. Urolithin B has none. Its muscle result comes from muscle cells in a dish and from mice given 10 micrograms a day through a pump placed under the skin for 28 days.
What is the Urolithin B dosage?
No human dose established. Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose. 1 completed trial, 0 people given it
Is Urolithin B FDA-approved?
Not an approved drug. Sold as a supplement ingredient and as a research chemical. No registered human trial has given it to people.
Is urolithin B the same as urolithin A?
No. They are different molecules with different claimed actions. Urolithin A is said to clear out old mitochondria. Urolithin B is said to control muscle protein balance through the androgen receptor. Urolithin A has finished studies in people against a dummy. Urolithin B has never been given to a person in a study.
Does urolithin B build muscle?
In muscle cells in a dish, and in mice getting a nonstop dose from a pump under the skin, yes. In people, nobody knows, because it has never been tested. The mouse dose was 10 micrograms a day, given nonstop, which does not carry over to a capsule.
Will eating pomegranate give me urolithin B?
Maybe, depending on your gut bacteria. People differ in which urolithins they make from these plant compounds. That is exactly why researchers moved to giving specific urolithins instead of the foods.
Is urolithin B safe?
Nobody knows. There is no human safety data, no data on how the body handles it, and no dose that anyone has studied in a person. No reported harm, in a compound nobody has studied in people, is not a safety record.
Why is it cheaper than urolithin A products?
Both the chemistry and the evidence. It is a simpler molecule, and it has none of the study program the branded urolithin A ingredient has behind it. You pay less because there is less to pay for.