Quick answer

NIH's LactMed database says the most common complaint with fish oil while nursing is belching a fishy taste, and that breast milk odor is not changed. NIH adds that it is not clear whether supplements taken while breastfeeding affect a baby's health. Ask your doctor before taking any omega-3 supplement while breastfeeding.^1,2

Key facts

LactMed says what a mother eats sets the EPA and DHA in her milk, and that supplements raise those levels within hours.¹
Published studies have found EPA and DHA in human milk, and supplements raise the amounts in milk, according to the label of a prescription omega-3 medicine.³
The same label says no data are available on the effects of omega-3 fatty acid ethyl esters on the breastfed infant.³
A 2021 systematic review of 15 trials judged the evidence inconsistent or insufficient for omega-3 supplements taken during lactation.⁴
FDA and EPA advise 2 to 3 servings a week of lower-mercury fish while breastfeeding, at 4 ounces a serving.⁵
NIH says people who are or might be breastfeeding should not take high-dose supplements of preformed vitamin A, which cod liver oil contains.^6,7

What does NIH say about omega-3 and breastfeeding?

NIH's consumer fact sheet puts pregnancy and breastfeeding together. It says it is not clear whether taking dietary supplements that contain EPA and DHA during either affects a baby's health or development. It also points out that breast milk contains DHA, and that most commercial infant formulas in the United States contain it too.²

The same sheet lists a recommended amount of the plant omega-3 called ALA for breastfeeding teens and women, which is a food-based figure and a different thing from fish oil. It sets no recommended amount for EPA or DHA.²

What does a prescription omega-3 label say about breast milk?

Few official documents speak to breastfeeding directly, and the label of a prescription omega-3 medicine is one. It says published studies have detected omega-3 fatty acids, including EPA and DHA, in human milk, and that women who take omega-3s as supplements have higher levels of them in their milk.³

The label also says no data are available on the effects of the medicine on the breastfed infant or on milk production, and that the benefits of breastfeeding should be weighed with the mother's need for the medicine. The patient leaflet adds that the medicine can pass into breast milk and tells readers to talk with a healthcare provider about the best way to feed the baby.³

What does LactMed say about fish oil and breastfeeding?

LactMed is the National Library of Medicine's database on medicines and supplements during nursing. Its entry for marine oils, updated in August 2026, says maternal diet determines the DHA and EPA in breast milk, and that supplements raise the levels within hours, although the long-run level depends more on regular intake than on the last few days.¹

On side effects, LactMed says the most common complaint while taking fish oil is belching a fishy taste after it is swallowed, and that the odor of breast milk is not changed by a mother's fish oil. It also reports two findings that a parent may want to raise with a doctor. In a long-term follow-up of a small group of children whose mothers took fish oil while nursing, boys had delayed puberty, a shorter average height and a higher systolic blood pressure at age 13. In another study, about 800 mg of DHA plus EPA a day for 6 months changed the infant gut microbiome, though no rise in infant illness was seen.¹

These are findings from a few studies, not warnings from a regulator, and LactMed does not tie them to a harm. They do show why the honest summary is that the question is still being studied.¹

What have reviews found about omega-3 supplements during lactation?

The 2021 systematic review for the US dietary guidelines committee looked at 33 articles from 15 randomized trials of omega-3 supplements given in pregnancy, in lactation or both, and measured child development. It reported inconsistent or insufficient evidence for supplementation during lactation, and it noted that the studies lacked racial and ethnic diversity and that adolescents were underrepresented.⁴

NCCIH describes a larger 2016 review of 143 studies of omega-3 supplements given to pregnant or breastfeeding women. Its authors found no effect on the other outcomes they examined, including growth after birth, visual acuity, long-term development and the later risk of autism, ADHD, learning disorders and allergies.⁸

What about fish and cod liver oil while breastfeeding?

For fish, FDA and the Environmental Protection Agency advise 2 to 3 servings a week from their Best Choices list, or 1 serving from the Good Choices list, with a serving measured as 4 ounces. Fish differ in mercury, which is why the advice comes with a chart.⁵

Cod liver oil is a different product from fish oil. NIH notes that cod liver supplements provide vitamin A and vitamin D as well as omega-3s, and its vitamin A fact sheet says that anyone who is or might be pregnant or breastfeeding should not take high-dose supplements of preformed vitamin A.^6,7

Who should ask a doctor before taking omega-3 while breastfeeding?

Anyone who is breastfeeding should ask a doctor, midwife or lactation specializt before adding a supplement. The sources are limited, and the questions below are the ones they raise.²

Which type of oil it is, because cod liver oil carries vitamin A.^6,7
Whether the mother has an allergy to fish or shellfish, since it is not known whether people with these allergies react to omega-3 made from fish oil.³
Whether the mother takes a blood thinner or aspirin, because high doses of omega-3s may cause bleeding problems with these medicines.²
Whether a prescription omega-3 medicine is involved, since its label asks mothers to weigh the benefits of breastfeeding against their own need for it.³

Questions people ask

Is fish oil safe while breastfeeding?

The label of a prescription omega-3 medicine says EPA and DHA appear in human milk and that no data exist on effects on the breastfed infant. NIH calls it unclear whether supplements change a baby's health. Ask your doctor before starting.^2,3

Is omega 3 ok while breastfeeding?

Eating fish is the part with firm advice: FDA and EPA suggest 2 to 3 servings a week from their lower-mercury list. For capsules, the sources checked leave the question open, so ask your doctor.^2,5

Are omega 3 supplements safe while breastfeeding?

A 2021 systematic review of 15 trials found inconsistent or insufficient evidence on supplements taken during lactation, so it cannot say either way. LactMed reports belching of a fishy taste as the most common complaint. Ask your doctor about your own situation.^1,4

Is omega 3 6 9 safe during breastfeeding?

The sources checked do not address omega 3 6 9 blends. That is not a finding either way, because NIH's omega-3 sheets cover ALA, EPA and DHA only. Ask your doctor or pharmacist to read the label of any blend.²

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This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.