Previously an NMN mice study showed 0.5g/L improved fertility while 2g/L reduced. 0.5g/L corresponds to about 6.67mg/kg in human. 2g/L corresponds to about 26mg/kg in human.
Here is a new mice dose study on NR. 30mg/kg and 180mg/kg have similar results. 900mg has worse results.
NR optimum dose is probably between 30 and 180. So pick 180 as the upper limit and divide by 12, we get human upper limit dose of NR of 15mg/kg. This is similar to the NMN study.
https://edepot.wur.nl/471911