Can I take diltiazem while pregnant or breastfeeding?
A plain-words look at what the NHS, the US drug label and LactMed say about diltiazem.
In short
Pregnancy: Diltiazem can be used in pregnancy, although it is not usually recommended.
Breastfeeding: Diltiazem can be taken while breastfeeding, provided your doctor or health visitor is happy that your baby is healthy.
Your doctor, midwife or pharmacist can help you decide.
What this means for you
Pregnancy
- If you take diltiazem for high blood pressure, you might be moved on to a different medicine once you're pregnant.
- If diltiazem is for angina or a heart rhythm problem, you should have a review with a heart specialist (cardiologist) and a pregnancy specialist (obstetrician).
- Keep taking diltiazem until that review has happened.
- If you use diltiazem for anal fissures, speak to your doctor, who may suggest a different medicine.
Breastfeeding
- Information on diltiazem in breastfeeding is limited, but some of it shows that tiny amounts reach breast milk.
- It's unlikely to harm your baby.
- Your doctor might, however, suggest another medicine that more is known about.
- If you use diltiazem cream or ointment, make sure you've washed your hands before you pick up your baby.
- If you breastfeed while taking diltiazem and your baby is not feeding as well as they usually do, seems unusually sleepy, looks paler than usual, or you're worried about your baby in any other way, contact your health visitor, midwife, pharmacist or doctor promptly.
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
Diltiazem in pregnancy
The NHS says
Diltiazem can be used in pregnancy, although it is not usually recommended.
If you take diltiazem for high blood pressure, you might be moved on to a different medicine once you're pregnant.
If diltiazem is for angina or a heart rhythm problem, you should have a review with a heart specialist (cardiologist) and a pregnancy specialist (obstetrician). Keep taking diltiazem until that review has happened.
If you use diltiazem for anal fissures, speak to your doctor, who may suggest a different medicine.
In our words, from the NHS page Diltiazem (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
Pregnancy Reproduction studies have been conducted in mice, rats, and rabbits. Administration of doses ranging from five to ten times greater (on a mg/kg basis) than the daily recommended therapeutic dose has resulted in embryo and fetal lethality. These doses, in some studies, have been reported to cause skeletal abnormalities. In the perinatal/postnatal studies, there was an increased incidence of stillbirths at doses of 20 times the human dose or greater. There are no well-controlled studies in pregnant women; therefore, use diltiazem hydrochloride in pregnant women only if the potential benefit justifies the potential risk to the fetus.
Prescribing label, section “Pregnancy”: diltiazem hydrochloride (oral), Golden State Medical Supply, Inc. Label on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.
Diltiazem while breastfeeding
The NHS says
Diltiazem can be taken while breastfeeding, provided your doctor or health visitor is happy that your baby is healthy.
Information on diltiazem in breastfeeding is limited, but some of it shows that tiny amounts reach breast milk. It's unlikely to harm your baby. Your doctor might, however, suggest another medicine that more is known about.
If you use diltiazem cream or ointment, make sure you've washed your hands before you pick up your baby.
If you breastfeed while taking diltiazem and your baby is not feeding as well as they usually do, seems unusually sleepy, looks paler than usual, or you're worried about your baby in any other way, contact your health visitor, midwife, pharmacist or doctor promptly.
In our words, from the NHS page Diltiazem (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
Based on limited data, amounts of diltiazem ingested by the infant are small and would not be expected to cause any adverse effects in breastfed infants.
“Summary of Use during Lactation”, LactMed record “Diltiazem” (LM94), quoted verbatim. Everything LactMed reports about Diltiazem while breastfeeding.
The US prescribing label says
Nursing Mothers Diltiazem is excreted in human milk. One report suggests that concentrations in breast milk may approximate serum levels. If use of diltiazem hydrochloride extended-release capsules is deemed essential, an alternative method of infant feeding should be instituted.
Prescribing label, section “Nursing Mothers”: diltiazem hydrochloride (oral), Golden State Medical Supply, Inc. Label on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.
Other names
UK brand names (per the NHS): Adizem, Angitil, Tildiem, Viazem, Zemtard.
Sources
- NHS, Diltiazem (nhs.uk), page last reviewed 10 March 2023. Paraphrased. Contains public sector information licensed under the Open Government Licence v3.0.
- US drug label: diltiazem hydrochloride (oral), Golden State Medical Supply, Inc., human prescription drug, label effective 27 August 2026, set ID 5a0f67ad-17d8-a3f4-e063-6394a90afb32. 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 “Diltiazem” (LM94), 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.