Breastfeeding Alcohol Calculator (When Is Breast Milk Alcohol-Free?)
Estimate how long to wait after drinking before breast milk is alcohol-free, from your weight, height and drinks, using the Motherisk method (Watson body water and 15 mg/dL per hour elimination), with a table for 1 to 5 drinks.
How it works
body water (L, Watson, women) = −2.097 + 0.1069 × height (cm) + 0.2466 × weight (kg) · peak blood alcohol (g/dL) = grams of alcohol × 0.8 ÷ body water ÷ 10 · hours until zero = peak ÷ 0.015 g/dL per hour · grams of alcohol = mL × ABV × 0.789
Alcohol passes freely into breast milk, and the level in milk mirrors the level in your blood: it rises after drinking and falls as your liver clears it, at roughly 15 mg/dL per hour. Pumping and discarding does not remove it faster. The calculator uses the method behind the widely used Motherisk table (Ho et al., 2001): Watson's body-water formula from your height and weight gives the peak level, and dividing by the elimination rate gives the time until no alcohol remains. Counting from the start of drinking is conservative because absorption is not instant.
Worked example
A breastfeeding parent who weighs 60 kg and is 163 cm tall has about 30.1 L of body water. One standard drink (14 g of alcohol) gives a peak of about 0.037 g/dL, which takes 2 h 29 min to clear, so waiting 2 h 29 min from the first sip means the milk is alcohol-free. Two drinks take about 4 h 57 min.
Sources: Ho E, et al. Alcohol and breast feeding: calculation of time to zero level in milk. Biol Neonate 2001 · CDC: Alcohol and breastfeeding · LactMed: Alcohol
Frequently asked questions
How long after a drink can I breastfeed?
For an average woman, about 2–3 hours per standard drink, counted from when you started drinking. The CDC says waiting at least 2 hours after a single drink before nursing minimises the baby's exposure. Smaller women and more drinks mean longer waits.
Do I need to pump and dump after drinking?
No. Alcohol is not trapped in the breast — it leaves milk as your blood alcohol falls. Pumping only helps comfort if you are full while waiting; discard that milk only if it was pumped while alcohol was still present.
Is it safe to have one drink while breastfeeding?
Not drinking is safest, but the CDC notes that moderate drinking (up to one drink a day) is not known to be harmful to the baby, especially if you wait at least 2 hours before nursing. Heavier drinking affects the baby's sleep, development and your milk supply.
Does food change the waiting time?
Eating slows absorption and lowers the peak somewhat, but it does not change how fast your liver clears alcohol. This calculator assumes all the alcohol is absorbed at once, which errs on the side of caution.
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Educational information only, not medical advice or a diagnosis. Discuss your results and any decision with your doctor, midwife or pharmacist.