Who should not take it, what to watch for, and the one interaction that matters most.

• Never combine it with serotonergic drugs on your own. The FDA label's boxed warning says that with SSRIs, SNRIs, or MAOIs it may cause serious or fatal serotonin syndrome.
• People with G6PD deficiency should not take it. The FDA label lists it as a contraindication because methylene blue can trigger hemolytic anemia.
• Supplements are for adults who are not pregnant or nursing. Nutricel products are not for use under 18.

Important: Methylene blue has documented interactions with serotonergic medications including SSRIs and MAOIs. Review the full adverse medications list before starting any methylene blue protocol.

The FDA label for Provayblue carries a boxed warning, its strongest kind: methylene blue may cause serious or fatal serotonin syndrome when combined with serotonergic drugs such as SSRIs, SNRIs, and MAOIs.^[1,13]

The reason is the MAO-A inhibition covered in Module 3. Methylene blue slows the breakdown of serotonin, and these medications raise serotonin too. Together they can push it dangerously high.

If you take any antidepressant or other serotonergic medication, do not take methylene blue without your doctor's explicit direction. We will not soften this one.

Serotonergic drugs are not only antidepressants. The FDA label lists categories that also include some medications for migraines, pain, cough, and anxiety, among others.^[1]

We keep a list of common medications on our adverse medications page so you can check before you start. It is a starting point, not a complete medical review.

If you take any prescription medication at all, the safest move is to bring the label to your doctor or pharmacist.

Adverse medications list →

G6PD deficiency is a genetic condition that makes red blood cells easier to damage. The FDA label lists it as a contraindication, because methylene blue can trigger hemolytic anemia in people who have it.^[1,12]

Many people with G6PD deficiency do not know they have it. It is more common in people of African, Mediterranean, Middle Eastern, and Asian descent.

If you do not know your status and have a family history, ask your doctor for a simple blood test before using methylene blue.

The FDA label states that methylene blue may cause fetal harm, and it advises against breastfeeding for up to 8 days after treatment. Methylene blue supplements are not for anyone who is pregnant or nursing.^[1]

Our products are formulated for adults only and are not for use under 18. Keep them out of reach of children, especially the liquid.

If you are planning a pregnancy, stop and talk to your provider.

The FDA label lists the most common effects at hospital amounts: blue-green urine, pain in the arms or legs, a changed sense of taste, feeling hot, dizziness, sweating, nausea, skin discoloration, and headache.^[1]

At supplement amounts, the one almost everyone notices is the urine color. Some people also report trouble winding down if they take it late in the day.

If anything feels wrong, stop taking it and contact your doctor.

The FDA label calls for caution in people with severe kidney impairment, because the kidneys clear much of each dose. Liver problems are worth a conversation too.^[1,12]

Methylene blue can affect pulse oximeter readings, the clip on your finger that measures oxygen. If you have a procedure scheduled, tell your care team you take it.

When in doubt, stop a few days before any planned surgery and let your surgeon know.

One interaction outranks everything else with methylene blue: serotonergic medications. Beyond that, a few groups should skip it, and a few situations call for a talk with your doctor first.

• Serotonergic drugs include some medications for migraines, pain, cough, and anxiety, as well as antidepressants.
• Check the adverse medications list, then take your prescription labels to your doctor or pharmacist.
• At supplement amounts, blue-green urine is the effect almost everyone notices.
• Severe kidney impairment calls for caution, and liver problems are worth a conversation too.
• It can affect pulse oximeter readings, so tell your care team before any procedure.

Clinical and regulatory

Peer-reviewed research and history