Urolithin A Side Effects and Safety

The short answer

Urolithin A has a reassuringly clean safety profile in the human research to date. Clinical trials — including the first-in-human safety study — found it well tolerated, with side effects generally mild, infrequent, and comparable to placebo. It’s a compound your own gut bacteria already produce from foods like pomegranates and walnuts, which is part of why it’s biologically familiar to the body.

What the research shows on safety

The landmark first-in-human trial specifically evaluated safety and found Urolithin A safe and well tolerated across the doses studied, with a favorable profile. Subsequent randomized trials in older and middle-aged adults reported no significant safety concerns. For a supplement, that’s a stronger safety dataset than most. (Background in the full Urolithin A guide.)

Possible side effects

When side effects do occur, they’re typically mild and digestive — the usual suspects for any oral supplement:

• Mild digestive upset — occasional bloating, gas, or stomach discomfort, especially at higher doses.
• Nausea — uncommon and usually mild.
• In trials, reported side effects were generally similar to placebo, meaning they weren’t clearly attributable to Urolithin A itself.

Taking it with food can help minimize any digestive discomfort.

Who should be cautious

Even with a clean profile, some groups should get medical guidance first:

• Pregnant or breastfeeding — not enough data; the default is to avoid.
• People on medications or with health conditions — as with any supplement, check for interactions.
• Anyone starting a new supplement — begin at a standard dose rather than megadosing.

Long-term safety

Human trials have run for several months without notable safety signals, which is encouraging. As with most newer supplements, very-long-term (multi-year) data is still accumulating — a reasonable caveat, not a red flag.

Bottom line

Urolithin A is among the better-tolerated supplements in the mitochondrial space, with side effects that are mild, uncommon, and often indistinguishable from placebo. Take it with food, stick to standard doses, and — if you’re pregnant, breastfeeding, or on medication — clear it with a clinician first.

Educational information only — not medical advice. Consult a clinician if you’re pregnant, breastfeeding, taking medication, or managing a health condition.