Many new mothers worry: Can I take this medication while breastfeeding? The fear isn’t irrational - you’re not just treating yourself, you’re protecting your baby too. But here’s the truth: most medications are safe. In fact, less than 5% of drugs are truly contraindicated during breastfeeding. The real problem isn’t the medicine - it’s the misinformation. Too many moms stop nursing because a doctor says, “Better safe than sorry,” when the evidence says otherwise.
What Makes a Medication Safe During Breastfeeding?
Not all drugs behave the same way in breast milk. Safety isn’t about whether a drug gets into milk - it’s about how much, how long it stays, and what it does to your baby. The key metric doctors use is the
Relative Infant Dose (RID). This measures how much of the drug your baby actually absorbs through breast milk compared to your dose. If the RID is under 10%, it’s generally considered low risk. Most common medications have RIDs under 2%.
For example, if you take 500 mg of ibuprofen, your baby might get about 1 mg through breast milk. That’s less than what you’d give a newborn for fever. And because many drugs don’t absorb well in a baby’s gut, even less makes it into their bloodstream.
The best resources for this data? LactMed, run by the U.S. National Library of Medicine, and the InfantRisk Center. These aren’t guesswork sites - they pull from peer-reviewed studies, pharmacokinetic models, and real-world infant monitoring. They tell you exactly how much drug ends up in milk, whether it’s been linked to side effects, and how long it lingers.
Pain Relief: Acetaminophen and Ibuprofen Are Your Go-To
If you’re dealing with headaches, sore muscles, or postpartum pain, acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) are the gold standard. Both have RIDs below 1%, meaning your baby absorbs almost nothing. They’re also safe for direct infant use - you’re giving your baby the same drug, just in a smaller dose.
Ibuprofen breaks down quickly in your body and doesn’t build up in milk. Acetaminophen is even cleaner - it’s excreted mostly through urine, with almost no trace in breast milk. Both are recommended by the American Academy of Family Physicians, Mayo Clinic, and the CDC. No need to time feedings. No need to pump and dump.
Skip naproxen (Aleve) for anything beyond a single dose. Its half-life is over 12 hours, and it’s been linked to rare cases of infant bleeding and anemia. Opioids? Avoid codeine completely. Some people metabolize it into morphine too quickly, and that can overdose a baby. Morphine and hydromorphone are safer if used short-term and at the lowest dose possible - but always monitor your baby for excessive sleepiness or trouble feeding.
Antibiotics: Most Are Fine - But Watch for Diarrhea
If you’ve got an infection, you’re not doing your baby any favors by skipping antibiotics. The good news? Penicillins like amoxicillin, cephalosporins like cephalexin, and vancomycin are all safe. Their RIDs are low, and there’s no evidence of long-term harm.
Macrolides like azithromycin are preferred over erythromycin. Erythromycin has a tiny risk of causing pyloric stenosis - a rare but serious condition that causes vomiting in infants. Azithromycin transfers minimally and has no such reports.
Fluoroquinolones like ciprofloxacin? Technically safe. Animal studies raised concerns about joint damage, but no human babies have shown issues. Still, they’re not first-line unless you really need them. Tetracyclines like doxycycline? Safe for short courses (under 21 days). Long-term use could theoretically affect tooth color, but no cases have been documented in breastfed infants.
Clindamycin? Use with caution. It can upset your baby’s gut and cause diarrhea. If you’re on it, watch for loose stools or fussiness.
Antidepressants and Anxiety Meds: Sertraline Leads the Pack
Postpartum depression affects 1 in 7 new mothers. Stopping breastfeeding to take medication shouldn’t be the trade-off. SSRIs are the most studied class, and sertraline (Zoloft) is the clear winner. Its RID is around 1.7-7%, but infant blood levels are often undetectable. It’s been used safely for decades, with no long-term developmental issues in follow-up studies.
Paroxetine (Paxil) is also safe, though slightly higher transfer. Fluoxetine (Prozac)? Avoid it if you can. Its half-life is 4-6 days. It builds up in your system - and in your baby’s. Studies show about 2% of exposed infants develop irritability or poor feeding.
For anxiety, lorazepam (Ativan) is the best benzodiazepine. Short half-life, low transfer. Clonazepam? Too long-lasting. It can make your baby sleepy or sluggish. Always use the lowest dose for the shortest time.
Antipsychotics like quetiapine (Seroquel) and risperidone (Risperdal) are also safe at standard doses. Long-term studies show normal growth and development in babies exposed through breast milk.
Allergy Meds: Skip the Old-School Antihistamines
Seasonal allergies? You don’t need to suffer. First-generation antihistamines like diphenhydramine (Benadryl) are a bad idea. They cross into milk easily, and babies can get drowsy, fussy, or even have trouble feeding. One study found 5% of infants exposed to Benadryl showed signs of sedation.
Stick to second-generation options: loratadine (Claritin), cetirizine (Zyrtec), and fexofenadine (Allegra). All have RIDs under 0.5%. No sedation. No feeding issues. No documented side effects in over 150 case reports.
Nasal sprays like fluticasone (Flonase) and budesonide (Rhinocort) are even better. They’re designed to act locally in your nose. Less than 1% enters your bloodstream - so almost nothing reaches your milk. Perfect for runny noses and congestion.
Avoid pseudoephedrine (Sudafed). It reduces milk supply by up to 24% in many women. That’s not a small drop - it’s enough to make breastfeeding unsustainable. Use saline sprays or steam inhalation instead.
What to Avoid Completely
There are a few drugs that truly aren’t safe. Radioactive iodine (I-131) for thyroid treatment? You must stop breastfeeding for 3-6 weeks. The radiation can damage your baby’s thyroid. No exceptions.
Chemotherapy drugs? Almost all require you to pause breastfeeding. The risk of long-term damage to a developing infant is too high. Talk to your oncologist - some newer targeted therapies may allow limited breastfeeding, but only under strict monitoring.
Lithium? It’s tricky. It passes into milk at 30-50% of your blood level. Infants can build up toxic levels quickly. If you’re on lithium, your baby needs weekly blood tests to check levels. If you can’t do that, formula may be the safer choice.
Herbal supplements? Don’t assume they’re safe. Many haven’t been studied in breastfeeding women. St. John’s Wort, for example, can cause colic or irritability. Kava and valerian can cause drowsiness. Always check with a provider before taking anything labeled “natural.”
What to Do If You’re Unsure
If you’re prescribed something new, don’t guess. Don’t rely on Google or a friend’s opinion. Use LactMed - it’s free, updated quarterly, and backed by the NIH. Type in the drug name, and you’ll get: RID, milk-to-plasma ratio, infant blood levels, and documented side effects.
Call the InfantRisk Center (1-806-352-2519). They’re staffed by pharmacists and researchers who specialize in lactation. They answer over 15,000 calls a year. No judgment. No sales pitch. Just facts.
Talk to your pediatrician. Ask: “Is this safe for a baby this age?” Not “Can I take this while breastfeeding?” The answer will be clearer if you frame it around your baby’s health.
Myth: If It’s Safe for Babies, It’s Safe for Breastfeeding
This is a useful rule of thumb - and it’s mostly true. If a drug is approved for infants, it’s likely safe in breast milk. But there are exceptions. Some drugs are safe for babies to swallow - but not safe if they’re absorbed through milk over weeks. Lithium is one. Others, like certain antivirals or immunosuppressants, may be okay for older infants but risky for newborns.
Always verify. The rule helps you eliminate the obvious dangers - but it doesn’t replace evidence.
Final Thought: Breastfeeding Is Worth Protecting
About 10-15% of mothers stop breastfeeding because they think a medication isn’t safe. In most cases, that decision is based on outdated advice or fear, not science. You’re not being selfish by taking a needed medication. You’re being responsible.
Your health matters. Your mental health matters. Your ability to care for your baby matters. There’s almost always a safe option. You just need the right information.
Use LactMed. Talk to a specialist. Ask questions. Don’t let misinformation cost you the benefits of breastfeeding - for you, and for your baby.
Juan Reibelo
24 01 26 / 04:08 AMI used to panic every time I needed an antibiotic-until I found LactMed. Now I check before I take anything. Seriously, it’s free, it’s scientific, and it saved my breastfeeding journey. No more guessing. No more tears. Just facts.
My OB told me to stop nursing for ibuprofen. I cried for an hour. Then I looked it up. Turns out, I was giving my baby less than a drop of the stuff. I felt so stupid-and so relieved.