Carbon 13 is a natural, stable and non-radioactive isotope (Idifarm 2016, Osaka 2016) that is used to label urea for diagnostic purposes. Since the last update we have not found any published data on its excretion in breast milk. Urea is a natural component of the body and is also found in milk (Wheeler RA 1991, Ross SA 1985). The dose of urea from the breath test to rule out infection by helicobacter pylori is 100 mg, an inconsequential amount since the endogenous production of urea is 25-35 g daily (AEMPS 2004). Manufacturer's data indicate low risk for pregnancy and breastfeeding (Idifarm 2016, Isomed 2004).