Cannabis and Lactation: Separating Fact from Fear

For decades, people have been told that using cannabis while lactating is dangerous and irresponsible. Yet, scientific research on the topic is limited, and what we do know doesn’t align with the fear-based messaging often pushed by healthcare providers and policymakers.

So, what does the research actually say about THC in human milk, its effects on infants, and whether lactating parents should avoid cannabis altogether?

How Much THC Passes Into Human Milk?

One of the biggest concerns around cannabis and lactation is the potential transfer of THC into human milk. But here’s what the science tells us:

• The amount of THC that actually makes it into human milk is extremely low.

• Doctors try to keep medication transfer in human milk below 10%. Relevant Infant Dose (RID) shows how much a baby gets, and 10% or less is typically safe.

• Studies estimate a 2.5% transfer rate, meaning that if a parent consumes cannabis, only a tiny fraction of the THC reaches the baby. Cannabis is transferred at a much lower rate than the relevant infant dose.

• The concentration is measured in nanograms—to put it in perspective, 1 gram equals 1,000,000,000 (1 billion) nanograms, so the amount making its way into human milk is incredibly small.

  —For example: Someone takes 40 mg of a medication/cannabis with a transfer rate/RID of 2.5%. That means about 1 mg could pass into their milk. Since milk is produced gradually, the actual amount in say a 4 oz (120 mL) feeding would be tiny—less than a grain of salt dissolved in water. It’s like adding a single drop of food coloring to a swimming pool—it’s there, but extremely diluted.

This low transfer rate suggests that clinically significant doses in infants are rare. (Baker & Hale, 2018).

What About THC Staying in Human Milk?

There is a lot of misinformation about how long THC lingers in human milk. Some early studies suggested that cannabis could stay in milk for weeks, but those findings were based on limited data.

A 2018 study by Bertrand et al. tested 54 human milk samples and found that THC was present in 63% of samples for up to six days after the last use, with a median THC concentration of 9.47 ng/mL (Bertrand et al., 2018).

This means that while THC can be detected, the levels decline over time.

How Does Cannabis Use Compare to Other Substances?

When discussing cannabis use during lactation, it’s important to compare it to other substances that are widely accepted:

• Caffeine: Passes into human milk at a higher rate than THC, yet moderate coffee consumption is generally considered safe.

• Alcohol: Often discouraged while lactating, but it’s acknowledged that small amounts clear from the body over time.

• Pharmaceuticals: Many prescription medications—some with well-documented risks—are given the green light for lactating parents.

Yet, despite its low transfer rate and lack of proven harm, cannabis continues to be stigmatized.

What About Health Risks for Babies Fed Human Milk?

The big question remains: does cannabis in human milk actually harm infants?

A 2022 study on early preterm neonates found no significant differences in major health outcomes related to intraventricular hemorrhage (IVH) between infants exposed to cannabis and those who weren’t. Instead, factors like steroid use, delivery method, and gestational age had a much bigger impact (AAP, 2022).

Additionally, no studies have definitively linked THC in human milk to negative neurodevelopmental outcomes in children.

Why We Should Be Cautious About Discouraging Lactation

Human milk offers well-documented, lifelong health benefits for babies, including:

   •   Boosted immune system

   •   Lower risk of infections

   •   Improved gut health

   •   Reduced risk of obesity and chronic diseases later in life

Because of this, experts caution against telling lactating parents to stop providing human milk due to cannabis use unless there is clear, evidence-based reasoning.

There is currently no evidence to suggest that cannabis use lowers milk supply. While some substances are known to impact milk production, research has not shown a direct link between cannabis and decreased supply. Milk production is primarily regulated by hormone levels and the frequency of milk removal, and no studies have confirmed that cannabis interferes with these processes.

This means that telling a cannabis-using parent to stop lactating could do more harm than good, especially if it leads to formula feeding in situations where human milk is preferred.

Practical Considerations for Lactating Parents Who Use Cannabis

For those who choose to use cannabis while lactating, we always ask clients to consider these safety guidelines:

✔ Avoid getting excessively high while caring for your baby – Just like alcohol, being too impaired can affect responsiveness.

✔ Refrain from smoking around your baby – Secondhand smoke exposure is a concern for any inhaled substance.

✔ Change clothes after smoking – To reduce any residual exposure from smoke particles on clothing.

✔ Time your use strategically – THC peaks in human milk about 60 minutes after smoking or inhalation, and 1.5 to 3 hours after consuming edibles. **The THC concentration can stay elevated for a longer period (up to 6 hours or more) with edibles, as they are metabolized more slowly.

✔ Trust your instincts and monitor your baby – If your baby is feeding well, gaining weight, and meeting developmental milestones, those are the most important indicators of health.

The Bottom Line

The research on cannabis and lactation is still evolving, but the current evidence does not support the widespread fear and stigma surrounding its use.

• THC transfers into human milk at a very low rate.

• No studies have definitively linked THC exposure through human milk to negative outcomes in infants.

• Human milk has well-documented benefits that should not be dismissed lightly.

Instead of blanket policies that push fear over facts, parents deserve honest, science-backed information to make the best choices for themselves and their babies.

Have questions about cannabis, lactation, or other medications while feeding your baby? We’re here to help! As cannabis-informed doulas, we support informed decision-making without judgment. If you want to learn more or share how cannabis has impacted your lactation journey, feel free to reach out. Let’s navigate this together!