Urolithin A vs Urolithin B
Written by Aaron CuhaReviewed Sep 2026
The short answer
Urolithin B is sold on urolithin A's reputation. Urolithin A has human trials showing better muscle function in older adults. Urolithin B's muscle result comes from muscle cells in a dish, and from mice given 10 micrograms a day by an implanted pump for 28 days.
- Urolithin A people
- 0
- Urolithin A nulls
- 1
- Urolithin B people
- 0
- Urolithin B nulls
- 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.
2 completed trials, 0 people given it
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
First-hand reports are counted on each profile and never added together. This page sets two published records side by side. It does not pick a winner.
Column A
Urolithin AUrolithin A
A compound your gut makes from pomegranates and berries. In older adults it helped muscle stamina and strength on some tests, and missed on others. It is sold as a supplement.
Column B
Urolithin BUrolithin B, gut microbial metabolite of ellagitannins
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.
Side by side, on the facts we can check
| What we compare | Urolithin A | Urolithin B |
|---|---|---|
| Category | Muscle & Performance | Muscle & Performance |
| FDA status | Sold as a supplement (generally recognized as safe, or GRAS); not an approved drug | Not an approved drug. Sold as a supplement ingredient and as a research chemical. No registered human trial has given it to people. |
| Half-life | Several hours | Not established in humans. No human pharmacokinetic study of administered urolithin B exists. |
| Molecular weight | 228.2 Da | 212.2 Da |
| How it works | It turns on mitophagy. That is the cell's way of clearing out broken mitochondria, the parts that make energy. The result is a better energy supply, mostly in muscle. | 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. |
| Studies in people | 3 | 1 |
| Evidence | Limited: 2 completed trials, none stating how many people | Limited: 1 completed trial, none stating how many people |
| Legal status, US | Sold as a dietary supplement | Sold as a supplement |
Frequently asked questions
What is the difference between Urolithin A and Urolithin B?
Urolithin A: A compound your gut makes from pomegranates and berries. In older adults it helped muscle stamina and strength on some tests, and missed on others. It is sold as a supplement. Urolithin B: 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.
Which has stronger research evidence, Urolithin A or Urolithin B?
Each compound gets a band worked out from facts we counted, with the math shown. Urolithin A is Limited (2 completed trials, none stating how many people). Urolithin B is Limited (1 completed trial, none stating how many people). That counts how much has been done in people. It does not rate whether either one works, and neither one is called the winner.
Are Urolithin A and Urolithin B FDA-approved?
Urolithin A: Sold as a supplement (generally recognized as safe, or GRAS); not an approved drug. Urolithin B: Not an approved drug. Sold as a supplement ingredient and as a research chemical. No registered human trial has given it to people..
Reviewed Sep 2026. This page puts two published records side by side. It is for learning, and it is not medical advice. When this site shows a dose, it is the dose a trial or a clinic actually used, or what people say they did, with the source attached. None of it tells you what to take.