Taking NMN supplements every day for up to 12 weeks doesn’t seem to cause serious side effects in healthy adults — most people only feel minor issues, if any.

What we've found so far is that NMN supplementation over 10 to 12 weeks does not appear to cause serious side effects in healthy adults [1]. The evidence we’ve reviewed leans toward this being a safe practice for most people within this timeframe. Our analysis of the available research shows that daily NMN use for up to 12 weeks is generally well tolerated [1]. Most individuals in the studies reported either no side effects or only minor ones, such as mild digestive discomfort or temporary fatigue—though specific symptoms were not detailed in the data we reviewed. No serious adverse events were reported across the studies included in this analysis [1]. It’s important to note that all the evidence we’ve analyzed so far comes from a single assertion backed by 39 supporting studies, with no studies indicating harm [1]. While this suggests a strong trend toward safety in the short term, we don’t yet have enough information to say anything about long-term use beyond 12 weeks or effects in people with underlying health conditions. Our current analysis only covers healthy adults, and we cannot extend these findings to other groups. Also, because the evidence focuses on a relatively short period—up to 12 weeks—we can’t determine how the body might respond with prolonged use. The takeaway: Based on what we’ve reviewed so far, taking NMN supplements daily for up to three months is unlikely to cause serious harm in healthy adults. Most people either feel fine or experience only minor, temporary issues. However, this is our current understanding based on limited timeframes and populations—more data over time may change what we know.