THC, the main psychoactive component of cannabis, is excreted into breast milk in small quantities and can remain detectable for a prolonged period. Studies have shown that THC can be found in breast milk from as short as 6 days up to more than 6 weeks after cannabis use. The estimated half-life of THC in breast milk ranges from about 12 to 39 hours, with some research estimating an average half-life around 17 days. This means THC clearance from breast milk can take anywhere from approximately 2.5 days to over 6 weeks, depending on factors such as frequency of use, dosage, metabolism, and body fat content of the mother

. Because THC is fat-soluble, it tends to accumulate in the body’s fat stores and breast milk, which contains lipids, leading to a longer washout period compared to substances like alcohol. This accumulation means that even after the psychoactive effects have worn off, THC and its metabolites can still be detected in breast milk for weeks. "Pumping and dumping" breast milk after cannabis use is ineffective at eliminating THC from milk because of this prolonged presence

. The concentration of THC in breast milk varies widely among individuals and depends on factors such as the amount and frequency of cannabis use, the method of consumption, and individual metabolism. Peak THC levels in breast milk typically occur between 30 minutes to 2 hours after use, but no consistent peak time has been established, especially with repeated use throughout the day

. In summary:

• THC can stay in breast milk from about 6 days to over 6 weeks.
• The half-life of THC in breast milk averages around 17 days but can vary.
• THC accumulates in fat and breast milk lipids, prolonging its presence.
• "Pumping and dumping" does not effectively remove THC from breast milk.
• Waiting several hours (3-4) after occasional cannabis use before breastfeeding may reduce exposure but does not eliminate THC

Given the potential risks to infant development and the prolonged presence of THC in breast milk, health experts generally recommend abstaining from cannabis use during breastfeeding.