Methylene Blue During Pregnancy and Breastfeeding: What the Labels and Research Say

Pregnant people, breastfeeding people, and people trying to conceive are a group who should not use methylene blue on their own. The FDA label for the prescription product ProvayBlue states that it may cause fetal harm when given to a pregnant woman, and it says to stop breastfeeding during treatment and for up to 8 days afterward. No one has studied methylene blue supplements in pregnant or nursing people, so there is no data that says a supplement dose is safe. If you are in one of these groups, the answer is to talk to your OB, midwife, or clinician first, and the honest default is to not take it.

• Pregnancy. The ProvayBlue label says it "may cause fetal harm" and lists malformations and pregnancy loss in rats and rabbits at high oral doses.
• Breastfeeding. The label says there is no information on methylene blue in human milk or its effects on a nursing infant, and advises stopping breastfeeding for up to 8 days after treatment.
• No supplement-dose data. The human reports we could verify involve dye injected into the amniotic sac, not capsules or drops. That is a reason for caution, not a measure of oral risk.
• Already took some? Do not panic and do not take more. Stop, write down what and when, and call your OB or clinician. In the US, Poison Help is 1-800-222-1222.

Important: This article is education, not medical advice. Methylene blue also has documented interactions with serotonergic medications. See our safety overview and the full adverse medications list.

ProvayBlue is the FDA-approved prescription form of methylene blue. Per its label, it is an injection given into a vein, indicated for acquired methemoglobinemia, at a dose of 1 mg/kg. It is not a supplement, and this is the only place the FDA has written down what is known about methylene blue in pregnancy. So it is worth reading what the label actually says. We pulled the current text from DailyMed (label version published June 12, 2025).

Under Use in Specific Populations, the label's Pregnancy section opens with a risk summary. It states that ProvayBlue "may cause fetal harm when administered to a pregnant woman." It also says intra-amniotic injection (into the amniotic sac) of a methylene blue class product during the second trimester was associated with neonatal intestinal atresia and fetal death. The highlights section adds that it should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus.

The Lactation section of the ProvayBlue label is short. It says there is no information regarding the presence of methylene blue in human milk, the effects on the breastfed infant, or the effects on milk production. Then it gives its advice: because of the potential for serious adverse reactions including genotoxicity, discontinue breastfeeding during and for up to 8 days after treatment.

Two things stand out. First, the label is not saying it has measured a problem in nursing infants. It is saying nobody knows, and that the unknowns are serious enough to recommend stopping. Second, the 8-day window is tied in the label to its Clinical Pharmacology section, which lists a half-life of approximately 24 hours in humans. We are not going to turn that into our own rule for supplement users. The point is that even the prescribers' label treats this as a many-day question, not a same-day one.

If you are nursing, that does not make your decision to take any supplement a small one. Talk to your pediatrician or lactation consultant as well as your own clinician, since the person on the receiving end is an infant.

Here is everything we could verify, and what kind of evidence each piece is.

Human reports, amniotic dye. Methylene blue has been injected into the amniotic sac during amniocentesis, especially in twin pregnancies, to tell the two sacs apart. A retrospective cohort study in New South Wales, Australia, looked at twin pregnancies with amniocentesis from 1980 through 1991 and compared those exposed to the dye with those not exposed. In the authors' words, dye use during mid-trimester amniocentesis in twin pregnancy "is associated with a high risk of small intestinal atresia." Fetal death occurred in 31.8 per cent of pregnancies exposed to a high concentration of dye, 14.5 per cent with a low concentration, and 4.3 per cent with no dye (Kidd et al., Prenatal Diagnosis, 1996).

Human case report, newborn hemolysis. A single case report described a newborn who developed hemolytic jaundice requiring exchange transfusion after intra-amniotic injection of methylene blue. With no other cause found, the author called methylene blue strongly implicated and said its use for that purpose should be avoided (Crooks, Archives of Disease in Childhood, 1982).

Animal studies, oral dosing. The label summarizes studies where methylene blue was given by mouth to pregnant rats (50 to 350 mg/kg per day) and rabbits (50, 100, or 150 mg/kg per day) during organogenesis, the period when organs form. In rats, maternal and embryo-fetal toxicity showed up at every dose, including reduced fetal weight, post-implantation loss, edema, and malformations such as enlarged lateral ventricles. In rabbits, maternal death occurred at 100 mg/kg, spontaneous abortion at all dose levels, and umbilical hernia at the 100 and 150 mg/kg doses.

A fair reading needs both sides. The animal doses were at least 16 to 32 times the label's 1 mg/kg clinical dose, and the dye injections are a different route than swallowing a capsule. Neither fact turns into a safety finding. Higher-than-clinical animal doses harming fetuses tells you the compound can affect development. Injected dye harming fetuses tells you it can reach one. What nobody has done is test the amounts and route a supplement user would take. For readers who want a broader review, a CDC-authored teratogen update on methylene blue was published in Teratology in 1999.

It is easy to assume a low dose must be a safe dose. The trouble is that "low" only means something when somebody has measured it. For pregnant and breastfeeding people, that measuring has not happened, and it is unlikely to.

• Pregnant people are rarely enrolled in supplement studies. Researchers avoid exposing a fetus to an unstudied compound, for the reasons above.
• The label says so directly for lactation. Its own summary is "no information" on milk transfer, infant effects, or milk supply.
• The label also says fertility studies have not been conducted. In its nonclinical toxicology section it notes methylene blue was genotoxic in bacterial and in vitro cell assays and reduced human sperm motility in vitro, which is a lab dish finding, not a statement about what happens in a person.
• Supplement quality varies. A capsule labeled with a dose has not gone through drug-approval testing. See our post on methylene blue quality red flags for how to read a label.

So the honest position is not "it is probably fine at a small dose" and it is not "it is proven dangerous at a small dose." It is that the question has not been answered, and the published material that does exist (the FDA label, the amniotic dye reports, the animal studies) points toward caution. When the stakes are a pregnancy or a nursing infant, unanswered is a reason to wait. For the general safety picture for other adults, see our Is Methylene Blue Safe? post.

G6PD (glucose-6-phosphate dehydrogenase) deficiency is an inherited enzyme deficiency. The ProvayBlue label lists it as a contraindication because of the risk of hemolytic anemia. It also states that treating patients with G6PD deficiency with ProvayBlue may result in severe hemolysis and severe anemia.

Why does that matter here? Hemolysis, meaning red blood cells breaking down faster than the body can replace them, also shows up in the pregnancy section of the label. Newborns exposed to a methylene blue class product by intra-amniotic injection hours to days before birth can develop hemolytic anemia and hyperbilirubinemia, among other problems. The Crooks case report above is an example of that pattern in one baby.

Many people have never been tested for G6PD status, which means they do not know which side of the contraindication they are on. The same goes for a baby. We did not find a source we could verify on whether methylene blue passing through breast milk is a risk for a G6PD-deficient infant, so we are not going to make a claim in either direction. The practical takeaway is that this is one more reason to have the conversation with your clinician before any exposure. Ask whether G6PD testing makes sense for you or your baby. For the adult side of this, see our G6PD deficiency guide and our methylene blue side effects overview.

This is the group people forget. Early pregnancy can go unnoticed for a few weeks, and the animal studies in the label dosed during organogenesis, which is exactly that early window. So if you are trying to conceive, the question is not only what to do once you see a positive test.

• The label gives no guidance on a washout before conception. It lists no conception-timing rule, and it says fertility studies have not been conducted. We will not invent one.
• The one number the label does give is a half-life of approximately 24 hours in humans (Clinical Pharmacology section). How long to wait is a question for your clinician, not for a blog post.
• Partners are part of the picture. The label notes that methylene blue reduced human sperm motility in vitro in a concentration-dependent way. That is a lab finding and it has not been tied to supplement use, but it is a fair thing to bring up with a fertility specialist or your clinician if you are taking it.
• Tell your OB or fertility clinician what you take. Include supplements, even ones you think are harmless.

Plenty of people read an article like this after the fact. If you took methylene blue and then found out you were pregnant, or you took it while nursing, here is a calm sequence. None of it is a substitute for medical care.

• Stop taking it. Do not take more while you sort this out.
• Write it down. The product name, how much, how many days or doses, the dates, and where you are in pregnancy or how old your baby is.
• Call your OB, midwife, or clinician. Bring the bottle or a photo of the label. If you are nursing, call your baby's pediatrician too.
• Use Poison Help if you want to talk to someone right away. In the US, the number is 1-800-222-1222, and the site describes it as free and confidential, at poisonhelp.org.
• List your other medications. Many people are on an SSRI or other serotonergic drug during pregnancy or postpartum, and the ProvayBlue label carries a serotonin syndrome warning for combining it with them. See our drug interactions guide.
• Do not stack fixes. Do not take other supplements, detox products, or home remedies to "flush it out."

The label says methylene blue may turn skin and body fluids blue. If you notice that, it is worth mentioning to your clinician as well as the amount you took. Mention it calmly. The goal is to give the person caring for you accurate information, not to panic over something that has already happened.

Quality matters for any supplement, and it matters more when the person taking it is pregnant, nursing, or about to be. If your clinician does clear methylene blue for you, they will want to know what is actually in the bottle. Look for independent third-party lab testing from a credentialed lab, not just a manufacturer-issued COA, and make sure the results include actual content verification, with purity and dose confirmed, rather than a generic pass/fail.

Nutricel publishes finished-product certificates of analysis for its capsule formulas, with heavy metals and microbial safety testing by independent labs including Eurofins Scientific. View our test results on the Nutricel certifications page. A lab report tells you what is in the bottle. It does not make a supplement safe in pregnancy.

Do not use methylene blue without your OB or clinician signing off if you are:

• Pregnant, or think you might be
• Breastfeeding or pumping for an infant
• Trying to conceive, or partnered with someone who is
• Known to have G6PD deficiency, or never tested and unsure
• Taking an SSRI, SNRI, MAOI, or other serotonergic medication (see the adverse medications list)

This applies to every form of methylene blue, including the capsules and liquid sold by Nutricel and everyone else. Our position is the same as the label's direction: no supplement use in these situations without medical guidance.

For pregnant, breastfeeding, and trying-to-conceive readers, the answer is none of them until your OB or clinician says otherwise. That includes Blue Boost, Blue Liquid, Blue Shroom, Blue Immune, Blue Renew, and Blue Remove. They all use the same methylene blue, so the same caution applies to all of them.

If your clinician does clear you for a supplement, bring the product page and the certificate of analysis to that appointment. Our certs page lists the lab reports. Whether it is appropriate for you is their call.

For readers who are not pregnant, breastfeeding, or trying to conceive, and who have cleared methylene blue with their clinician, this is how our products differ:

Blue Boost is Nutricel's core formula, a methylene blue capsule built around absorption and cellular energy.

Blue Immune combines methylene blue with copper, NAC, grass-fed beef liver, and vitamins A, C, and E.

Blue Shroom pairs methylene blue with six organic mushroom extracts including lion's mane, reishi, cordyceps, chaga, shiitake, and turkey tail.

Blue Renew is built around GlyNAC (glycine and N-acetyl cysteine) alongside methylene blue.

Blue Remove combines zeolite, curcumin, and nattokinase with methylene blue.

Blue Liquid delivers USP-grade methylene blue in a dropper bottle for liquid format.

Methylene blue has a real FDA label, and on pregnancy and breastfeeding that label says two things plainly: it may cause fetal harm, and nursing should stop for up to 8 days after treatment. The human evidence we could verify comes from injected dye, the animal evidence comes from high oral doses, and there is no study of supplement use at all. That gap is the reason for this page.

If you are pregnant, nursing, or trying to conceive, do not use methylene blue unless your OB or clinician tells you to. If you already did, stop, write down the details, and call them. You are not in trouble for having read the wrong thing earlier. You just now have the right thing to read.

FDA Label and Poison Control

Clinical and Case Literature

Further Reading

Sam Carlson, Marketing Developer at Nutricel

Sam is a marketing developer at Nutricel who writes the Nutricel Insights series to help our customers understand methylene blue and make informed choices, translating the published research into plain language. Sam is not a medical professional, and these articles are intended as education rather than medical advice. Every figure in this piece is tied to the studies listed in the references, and you should always speak with your healthcare provider before starting any supplement.