Can you take valacyclovir while breastfeeding?
What LactMed says
The National Library of Medicine’s own summary, quoted in full. We do not write a verdict of our own on this question, and we do not compress theirs into a label.
The dosage of acyclovir in milk after valacyclovir is less than 1% of a typical infant dosage and would not be expected to cause any adverse effects in breastfed infants. Valacyclovir is considered a treatment of choice for Herpes infections during breastfeeding. No special precautions are required when using valacyclovir during breastfeeding. In one study, administration of valacyclovir to mothers with concurrent herpes simplex type 2 and HIV infections reduced breastmilk shedding of the HIV virus in breastmilk at 6 and 14 weeks postpartum, but not later. In another study in HIV-positive mothers, valacyclovir did not reduced breastmilk shedding of cytomegalovirus (CMV) or infant CMV acquisition.
Quoted from Valacyclovir — Drugs and Lactation Database (LactMed®), National Institute of Child Health and Human Development, revised January 15, 2026.
What LactMed would consider instead
LactMed ends this record by naming the drugs it would consider in place of valacyclovir. Whether any of them fits depends on what you are treating — this is the database’s list, not a recommendation from us.
How much valacyclovir gets into breastmilk
Valacyclovir is a prodrug that is rapidly converted to acyclovir in the body.
Maternal Levels. Five mothers who were nursing neonates were given valacyclovir 500 mg orally every 12 hours for 5 days. Valacyclovir was not detected in milk. Median peak acyclovir concentrations in milk of 4.2 mg/L occurred at 2 to 4 hours after the first dose and was similar after the last dose. The authors calculated the median milk concentration at steady-state to be 2.24 mg/L. The median half-life in milk was 2.1 hours (range 1.3 to 12.2 hours). A 500 mg maternal dose of valacyclovir twice daily would provide a breastfed child with a daily oral acyclovir dosage of approximately 0.6 mg/kg. This is about 1% of the neonatal intravenous dose of acyclovir.
In a study of pregnant women with concurrent HIV and Herpes simplex infections, mothers received zidovudine 300 mg daily from week of pregnancy until 12 months postpartum and nevirapine at delivery. Half of the women (n = 74) also received valacyclovir 500 mg orally twice daily from 34 weeks gestation until 12 months postpartum. Milk samples (timing not stated) from 44 women obtained at 2 weeks postpartum found detectable acyclovir in 35 samples, with a median concentration of 2.6 mg/L (range 0.15 to 10.15 mg/L) Three of the 9 women with undetectable milk acyclovir levels had missed one or more doses of valacyclovir in the previous 2 days.
Infant Levels. The urine of 5 infants whose mothers were taking valacyclovir 500 mg every 12 hours orally was collected. Valacyclovir was not detected in any of the infant's urine. The median infant urine acyclovir concentration on day 5 of therapy was 0.74 mg/L.
What has been seen in breastfed infants
In a study of pregnant women with concurrent HIV and Herpes simplex infections, mothers received zidovudine 300 mg daily from week of pregnancy until 12 months postpartum and nevirapine at delivery. Half of the women (n = 74) also received valacyclovir 500 mg orally twice daily from 34 weeks gestation until 12 months postpartum. At 6 weeks postpartum, all infants who received acyclovir in breastmilk had normal serum creatinine (<0.83 mg/dL). Their median serum creatinine and alanine aminotransferase (ALT) values, and growth were no different from those of unexposed infants, with the exception of one infant with an ALT level of 70.1 units/L. Infants whose mothers received valacyclovir generally had adverse effects that were similar to the placebo group, except that treated infants had a lower risk of eczema and oral thrush than infants in the placebo arm.
Effects on milk supply
Relevant published information was not found as of the revision date.
Frequently asked questions
Can you take valacyclovir while breastfeeding?
What the NIH's Drugs and Lactation Database says about Valacyclovir while breastfeeding — quoted in full. The full record is quoted on this page, and the decision is one to make with the person who prescribed it — LactMed itself states it is not a substitute for professional judgement.
What can I take instead of valacyclovir while breastfeeding?
LactMed lists Acyclovir as alternate drugs to consider. That is the database's own list for this drug — whether any of them suits you depends on what you are treating.
Does valacyclovir pass into breastmilk?
LactMed's measured drug levels for valacyclovir are quoted in full on this page, under "How much gets into breastmilk".
Do I need to pump and dump after taking valacyclovir?
LactMed does not frame its records that way — it reports measured drug levels in milk and what has been observed in breastfed infants, which is what this page quotes. "Pump and dump" advice for a specific drug and dose should come from your clinician or a pharmacist, not from a general rule.
More on valacyclovir
LactMed states that the information it presents is not a substitute for professional judgement, and that you should consult your healthcare provider for breastfeeding advice related to your particular situation. Nothing on this page is medical advice.