Taking NR or NMN by mouth seems to be safe for people over several weeks or months, with no serious side effects seen so far in studies.

What we've found so far is that oral use of nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) appears to be safe for humans when taken over weeks to months [1]. Our analysis of the available research shows no serious side effects have been reported in the studies we reviewed [1]. We looked at 28 individual pieces of evidence, and all of them support the idea that NR and NMN are well-tolerated in people during short- to medium-term use [1]. These studies monitored participants taking NR or NMN daily for periods ranging from several weeks to several months, and no major safety concerns arose [1]. Most reports describe mild or no side effects, though specific details about minor reactions were not provided in the data we analyzed. Our current analysis does not include long-term use beyond several months, so we cannot say how safe these compounds might be over years. Also, the studies we reviewed focused on general safety, not specific health outcomes, so we are not evaluating whether NR or NMN improve health—only whether they appear safe in the timeframes studied. The evidence we've reviewed leans toward a favorable safety profile for oral NR and NMN supplementation in the short to medium term [1]. However, science is ongoing, and our understanding may change as more data becomes available. Practical takeaway: Based on what we've seen so far, taking NR or NMN by mouth for weeks or a few months doesn’t seem to cause serious harm, but we don’t yet know what might happen with much longer use.