Urolithin A Side Effects and Safety

The short answer

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

What the research shows on safety

The landmark first-in-human trial was built specifically to evaluate safety, and it found urolithin A safe and well tolerated across the doses studied. Later randomized trials in older and middle-aged adults reported no significant safety concerns. For a supplement, that’s a stronger dataset than most can point to. (Background in the full Urolithin A guide.)

Possible side effects

When side effects do show up, they’re usually 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 when it happens.
• 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, a few groups should get medical guidance first:

• Pregnant or breastfeeding: there isn’t enough data, so 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. That’s a reasonable caveat, not a red flag.

Doses used in the studies

The trials behind this safety profile mostly tested 500 mg to 1,000 mg per day, taken as a single daily dose. Side effects did not scale up meaningfully at the higher end of that range, which is part of why the data reads as reassuring rather than dose-dependent. When digestive discomfort does show up, it typically eases within the first week or two as the body adjusts. Starting at a lower dose before moving to a full dose is a reasonable approach if you tend to be sensitive to new supplements generally.

Who should be cautious, at a glance

Group	Guidance
Pregnant or breastfeeding	Avoid; insufficient safety data for this group
On medication or managing a health condition	Check for interactions with a clinician before starting
New to supplements generally	Start at a standard dose rather than the higher end of the studied range
Everyone else	Generally well tolerated at studied doses, per the trial data above

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.