Cannabis and Breastfeeding: THC in Breast Milk

Special Populations

6 Days

THC concentrates in breast milk because milk is high in fat, and the Bertrand 2018 study found it remains detectable for up to 6 days after a single use.

Pediatrics, 2018

Pediatrics, 2018

View as image

If you are breastfeeding and using weed, or thinking about whether you can, you are asking a question that more parents face than most people realize. THC in breast milk is a real concern backed by real research, and the answer is more nuanced than a simple yes or no. What the science does tell us clearly is that THC behaves very differently in breast milk than substances like alcohol, and the strategies that work for one do not work for the other.

This article covers what happens when THC enters breast milk, how long it stays there, what medical organizations recommend, and how to think through your options without judgment. If you used cannabis during pregnancy and are weighing your next steps, the guide on quitting weed while pregnant covers the prenatal side. This article picks up where that one leaves off: the postpartum period and breastfeeding specifically.

Why THC Concentrates in Breast Milk

THC is lipophilic, meaning it dissolves in and is attracted to fat. This single property explains almost everything about why cannabis and breastfeeding is a concern.

Breast milk is rich in fat. It is designed that way because your baby's rapidly developing brain needs large amounts of fat for growth. But that same fat content creates a problem: THC moves from your bloodstream into breast milk and concentrates there, sometimes at levels higher than what is circulating in your blood.

Your endocannabinoid system normally produces its own cannabinoids that play important roles in brain development, appetite regulation, and immune function. When external THC enters an infant's system through breast milk, it interacts with the same CB1 receptors that your baby's own endocannabinoids are supposed to be guiding. The concern is that this external THC could interfere with the delicate developmental processes those receptors are coordinating.

Unlike alcohol, which is water-soluble and clears from breast milk as your blood alcohol level drops, THC gets stored in fat tissue throughout your body. It is then slowly released back into your bloodstream, and therefore back into your breast milk, over an extended period. This is why the detection window is so much longer than most people expect.

The Bertrand 2018 Study: 6 Days of Detection

The most frequently cited research on THC in breast milk comes from Bertrand et al., published in 2018 in Pediatrics. This study measured THC concentrations in breast milk samples from 50 breastfeeding women who reported cannabis use.

The key finding: THC was detectable in breast milk for up to 6 days after use. This was true even for participants who used cannabis only occasionally. The study also found that the amount of THC in breast milk did not correlate neatly with frequency of use in a way that would allow calculating a "safe" amount. Some samples from occasional users still showed meaningful concentrations.

This 6-day window matters because it fundamentally changes the math on occasional use. If you are breastfeeding 8 to 12 times per day and THC persists in your milk for nearly a week, even using cannabis once a week means your baby is exposed to some level of THC during almost every feeding.

An earlier study by Baker et al. (2018) in Obstetrics and Gynecology reported similar findings and noted that THC levels in breast milk were highest in the first hour after use but remained present for days afterward. The initial spike followed by a long tail of exposure is consistent with how fat-soluble compounds behave in high-fat fluids.

Why Pump and Dump Does Not Work for THC

Many breastfeeding parents are familiar with the "pump and dump" strategy for alcohol. You have a drink, pump and discard milk for a set period, then resume feeding once the alcohol has cleared your system. This works for alcohol because it is water-soluble. As your blood alcohol level drops, the alcohol concentration in your milk drops in parallel. Within a few hours, it is gone.

THC does not work this way. Because it is stored in fat cells and released gradually, pumping and discarding a few sessions worth of milk does not meaningfully reduce your baby's exposure. THC is still present in the new milk your body produces hours or even days later. The fat cells in your breast tissue continue releasing stored THC into newly produced milk regardless of how much you pump and discard.

This is one of the most important distinctions for breastfeeding parents to understand. The pump and dump approach gives a false sense of security with THC. If you use cannabis and then pump and dump for 12 or even 24 hours, the breast milk you produce after that period will still contain detectable THC, potentially for several more days.

What Medical Organizations Say

The major medical organizations are aligned on this topic.

The American Academy of Pediatrics (AAP) updated its guidance in 2018, recommending that breastfeeding parents abstain from cannabis use. The AAP noted that while breast milk provides significant nutritional and immunological benefits, the data on THC exposure through breast milk raises enough concern to recommend avoidance.

The American College of Obstetricians and Gynecologists (ACOG) included lactation in its 2017 committee opinion on cannabis use during pregnancy, recommending that patients "discontinue marijuana use while breastfeeding."

The Academy of Breastfeeding Medicine (ABM) issued a 2015 protocol acknowledging insufficient data to establish safety and recommending that cannabis use during breastfeeding be minimized or avoided.

The consistent message across all three organizations: there is not enough evidence to declare any level of THC exposure through breast milk as safe, and the precautionary recommendation is to avoid it.

What We Know and Do Not Know About Infant Effects

This is where the research gets honest about its limits. The studies on long-term outcomes for infants exposed to THC through breast milk are limited, and separating the effects of postnatal exposure (through breast milk) from prenatal exposure (during pregnancy) is methodologically difficult. Many infants exposed through breast milk were also exposed in utero.

What we do know:

• THC reaches the infant. This is confirmed. The question is not whether your baby is exposed but how much that exposure matters.
• Infant metabolism of THC is immature. A newborn's liver is not fully equipped to process THC the way an adult liver does. This means THC and its metabolites may remain in an infant's system longer than they would in yours.
• The infant brain is in a critical development window. The first year of life involves massive neural growth, synapse formation, and myelination (the process of insulating nerve fibers so signals travel faster). The endocannabinoid system is actively involved in guiding these processes.

What we do not know:

• The minimum threshold for harm. No study has established a level of THC in breast milk that is definitively safe or definitively harmful.
• Long-term developmental outcomes at typical exposure levels. The longitudinal studies needed to answer this question are still underway or have not been conducted.
• Whether the effects of THC through breast milk are different from the effects of prenatal exposure. Most existing studies cannot cleanly separate these two variables.

This uncertainty is not reassurance. It is the honest state of the science. The absence of proven harm is not the same as evidence of safety, which is exactly why the AAP and ACOG default to recommending avoidance.

The Breastfeeding vs. Formula Decision

One of the hardest parts of this conversation is that it can feel like you are being asked to choose between breastfeeding and cannabis. Some parents take it a step further and wonder whether they should stop breastfeeding entirely so they can use cannabis for postpartum symptoms.

This is a real and valid tension. Breastfeeding has well-documented benefits for infant health, including immune support, nutritional optimization, and bonding. Postpartum anxiety, depression, pain, and sleep deprivation are also real, and for some parents, cannabis has been the thing that helps them function.

The medical recommendation is not "stop breastfeeding so you can use cannabis." It is "stop cannabis so you can breastfeed safely." But if postpartum symptoms are severe enough that you feel you cannot function without cannabis, that is a conversation to have with your healthcare provider about alternative treatments, not a situation to manage alone.

For more on how cannabis interacts with female hormones, including the postpartum hormone landscape, that guide covers the broader hormonal picture.

Postpartum Use and What Drives It

The postpartum period is genuinely difficult. Sleep deprivation, hormonal shifts, physical recovery from childbirth, and the relentless demands of a newborn create a perfect storm of stress. For people who used cannabis before or during pregnancy, the pull to resume use can be strong.

Common reasons postpartum parents consider cannabis:

• Sleep. Your baby is waking you every 2 to 3 hours. Cannabis helped you sleep before. The temptation is understandable.
• Anxiety. Postpartum anxiety affects roughly 10 to 15 percent of new parents and can be more debilitating than postpartum depression.
• Pain. Recovery from childbirth, especially cesarean birth, involves real physical pain.
• Mood regulation. The postpartum hormonal crash is significant, and cannabis can feel like a stabilizer.

All of these are legitimate struggles. None of them are best addressed with cannabis while breastfeeding. Postpartum-specific treatments exist for all of these concerns, and your OB, midwife, or a postpartum mental health specialist can help you find options that are compatible with breastfeeding.

If you are considering whether the proven medical benefits of cannabis outweigh the risks during breastfeeding, that article provides broader context on what cannabis can and cannot treat.

Secondhand and Thirdhand Smoke Exposure

If you have older children at home and are navigating questions about your cannabis use, the guide on how to talk to your teenager about weed offers a framework for honest, age-appropriate conversations.

Even if you avoid consuming cannabis while breastfeeding, smoking or vaping around your infant creates additional exposure routes. Secondhand cannabis smoke contains THC, and infants in enclosed spaces with cannabis smoke can absorb it through their lungs. Thirdhand exposure, where THC residue settles on surfaces, clothing, and skin, is another concern. Holding and feeding your baby shortly after smoking means THC residue on your hands and clothing comes into direct contact with your infant.

If anyone in your household uses cannabis, doing so away from the baby and changing clothes and washing hands before holding the infant reduces (but does not eliminate) these secondary exposures.

Making an Informed Decision

The science is clear enough to support a strong recommendation against cannabis use while breastfeeding, but it is also honest enough to admit what it does not yet know. You are the one who has to weigh this information against your specific circumstances.

Some questions worth considering:

• How frequently am I using cannabis, and can I stop or significantly reduce?
• What specific symptoms am I using it for, and have I explored breastfeeding-safe alternatives?
• Am I willing to switch to formula if I decide I need cannabis for my mental or physical health?
• Have I talked to my healthcare provider openly about both my cannabis use and my postpartum symptoms?

There is no version of this decision that is simple. But making it with accurate information, rather than assumptions about pump and dump or occasional use being fine, puts you in the best position possible.

When to Seek Professional Help

Talk to your healthcare provider if:

• You want to stop using cannabis while breastfeeding but are having difficulty quitting
• You are experiencing postpartum depression, anxiety, or other mental health symptoms that feel unmanageable
• You are using cannabis alongside other substances during the postpartum period
• You need help finding breastfeeding-safe alternatives for pain, sleep, or anxiety
• You are unsure whether to continue breastfeeding given your cannabis use

For guidance on the quitting process itself, the cannabis withdrawal complete guide covers what to expect and how to manage symptoms.

SAMHSA's National Helpline is available at 1-800-662-4357. It is free, confidential, and available 24 hours a day, 7 days a week. You can also text "HELLO" to 741741 to reach the Crisis Text Line.

You Deserve Accurate Information, Not Judgment

The decision to breastfeed while navigating postpartum challenges is already complicated enough without incomplete information about cannabis. You are not a bad parent for asking these questions. You are a parent trying to make the best decision with the information available.

The research tells us that THC concentrates in breast milk, persists for days, and cannot be pumped away. Medical organizations unanimously recommend avoiding cannabis while breastfeeding. At the same time, the postpartum symptoms that drive cannabis use are real and deserve real treatment. The goal is not to suffer through the postpartum period without support. It is to find support that does not expose your baby to a compound we cannot yet confirm is safe.

Whatever you decide, make sure it is based on what the science actually says, not on assumptions, guilt, or what someone told you at a support group. You and your baby both deserve that.