Can I take alendronic acid while pregnant or breastfeeding?
A plain-words look at what the NHS, the US drug label and LactMed say about alendronic acid.
In short
Pregnancy: Alendronic acid is not recommended in pregnancy, because its safety has not been researched enough.
Breastfeeding: Alendronic acid is usually OK to take while breastfeeding. Your doctor or pharmacist can help you make the decision, so speak to them first.
Your doctor, midwife or pharmacist can help you decide.
What this means for you
Breastfeeding
- Alendronic acid is usually OK to take while breastfeeding.
- Your doctor or pharmacist can help you make the decision, so speak to them first.
- Nobody knows exactly how much alendronic acid reaches breast milk, but the levels are likely to be very low.
- Little of it will reach your baby, so it's unlikely to cause them side effects.
- Side effects in breastfed babies from medicines their mother takes are very rare.
- Even so, it's important to keep an eye on your baby while you take any medicine and breastfeed.
- Until you've had advice about your baby's symptoms, keep taking alendronic acid and carry on breastfeeding as normal.
When to get help
- Contact a healthcare professional or call 111 (in the UK) as soon as you can if your baby is not feeding as well as they usually do; is irritable; is vomiting or has diarrhoea; or is constipated.
- If your baby has any other symptoms, or you're worried about them, you can still call 111 or get in touch with any healthcare professional.
Talk to your doctor or pharmacist
This page is educational, not advice for your own situation. Talk to your doctor, midwife or pharmacist before you start, stop or change any medicine in pregnancy or while breastfeeding.
The details: what each source says
Alendronic acid in pregnancy
The NHS says
Alendronic acid is not recommended in pregnancy, because its safety has not been researched enough.
In our words, from the NHS page Alendronic acid (nhs.uk). Contains public sector information licensed under the Open Government Licence v3.0 (OGL v3.0). The NHS does not endorse this site.
The US drug label says
8.1 Pregnancy Pregnancy Category C: There are no studies in pregnant women. Alendronate sodium should be used during pregnancy only if the potential benefit justifies the potential risk to the mother and fetus. Bisphosphonates are incorporated into the bone matrix, from which they are gradually released over a period of years. The amount of bisphosphonate incorporated into adult bone, and hence, the amount available for release back into the systemic circulation, is directly related to the dose and duration of bisphosphonate use. There are no data on fetal risk in humans. However, there is a theoretical risk of fetal harm, predominantly skeletal, if a woman becomes pregnant after completing a course of bisphosphonate therapy. The impact of variables such as time between cessation of bisphosphonate therapy to conception, the particular bisphosphonate used, and the route of administration (intravenous versus oral) on the risk has not been studied. Reproduction studies in rats showed decreased postimplantation survival and decreased body weight gain in normal pups at doses less than half of the recommended clinical dose.
Prescribing label, section “8.1 Pregnancy” (opening excerpt): ALENDRONATE SODIUM (oral), NuCare Pharmaceuticals,Inc. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.
Alendronic acid while breastfeeding
The NHS says
Alendronic acid is usually OK to take while breastfeeding. Your doctor or pharmacist can help you make the decision, so speak to them first.
Nobody knows exactly how much alendronic acid reaches breast milk, but the levels are likely to be very low. Little of it will reach your baby, so it's unlikely to cause them side effects.
Side effects in breastfed babies from medicines their mother takes are very rare. Even so, it's important to keep an eye on your baby while you take any medicine and breastfeed.
Contact a healthcare professional or call 111 (in the UK) as soon as you can if your baby is not feeding as well as they usually do; is irritable; is vomiting or has diarrhoea; or is constipated.
If your baby has any other symptoms, or you're worried about them, you can still call 111 or get in touch with any healthcare professional.
Until you've had advice about your baby's symptoms, keep taking alendronic acid and carry on breastfeeding as normal.
In our words, from the NHS page Alendronic acid (nhs.uk). Contains public sector information licensed under the Open Government Licence v3.0 (OGL v3.0). The NHS does not endorse this site.
LactMed says
Limited evidence indicates that breastfeeding after cessation of long-term bisphosphonate treatment appears to have no adverse effects on the infant. Because no information is available on the use of alendronate during breastfeeding, an alternate drug may be preferred, especially while nursing a newborn or preterm infant. However, absorption of alendronate by a breastfed infant is unlikely. If the mother receives a bisphosphonate during pregnancy or nursing, some experts recommend monitoring the infant's serum calcium during the first 2 months postpartum.[1]
“Summary of Use during Lactation”, LactMed record “Alendronate” (LM723), quoted verbatim. Everything LactMed reports about Alendronate while breastfeeding.
The US prescribing label says
Nursing Mothers It is not known whether alendronate is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when alendronate sodium is administered to nursing women.
Prescribing label, section “Nursing Mothers”: ALENDRONATE SODIUM (oral), NuCare Pharmaceuticals,Inc. Label on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.
Other names
UK brand names (per the NHS): Fosamax, Binosto.
US name: alendronate.
Sources
- NHS, Alendronic acid (nhs.uk), page last reviewed 7 May 2025. Paraphrased. Contains public sector information licensed under the Open Government Licence v3.0.
- US drug label: ALENDRONATE SODIUM (oral), NuCare Pharmaceuticals,Inc., human prescription drug, label effective 23 June 2026, set ID 54d6543d-4239-58b1-e054-00144ff88e88. DailyMed (National Library of Medicine). Public domain; quoted verbatim.
- Drugs and Lactation Database (LactMed), National Institute of Child Health and Human Development (NICHD), via NCBI Bookshelf, record “Alendronate” (LM723), bulk release of 22 September 2026. LactMed on NCBI Bookshelf. Public domain; quoted verbatim. LactMed is a registered trademark of the U.S. Department of Health and Human Services.
Sources checked 26 September 2026. How we source and check every page.
Educational summary of named sources, not medical advice.