Compounded Methylene Blue

Compounded methylene blue is prepared for you by a licensed compounding pharmacy in our clinical partner's network and is not FDA-approved. It is not a brand-name or generic product, and the FDA has not reviewed it for safety, effectiveness or quality. Methylene blue is FDA-approved only as an intravenous treatment for acquired methemoglobinemia (the brand-name ProvayBlue); taking methylene blue by mouth for any other purpose is an off-label use, which your provider will explain.

Methylene blue is a dye first made in 1876 that works as a redox cycler: it accepts electrons from the cell's NADH-dependent enzymes and hands them on. At the intravenous doses of the approved product, that is how it converts methemoglobin — hemoglobin that has lost the ability to carry oxygen — back to a working form, which is its one approved use. Inside mitochondria the same property lets it carry electrons between the complexes of the respiratory chain, and that is the mechanism providers cite for low-dose oral use. It is also a reversible inhibitor of monoamine oxidase A, the enzyme that breaks down serotonin, which is why combining it with an antidepressant or certain opioids can cause serotonin syndrome, a potentially fatal reaction that carries a boxed warning on the approved product. The dose matters: low doses act as an electron carrier, high doses as an oxidant. Human outcome data for oral low-dose use comes from small, short studies and does not support any specific promise — we describe the mechanism here, not a result.

1. 01

   Days 1–3

   Your urine turns blue or blue-green — expected and harmless, and stool can tint too. Tell any clinician who orders a urine test or uses a pulse oximeter that you take it, because the dye can interfere with both.

2. 02

   Weeks 1–4

   Nausea, stomach upset or a headache are the common early experiences and usually settle. Any new medication — including an over-the-counter cough remedy — is checked with the care team before you take it.

3. 03

   Ongoing

   Reviewed at check-ins like any prescription. Because the interaction risk never goes away, the medication review at each refill is not a formality.

Blue-green urine, and sometimes a bluish tint to stool or skin, is universal and harmless. Nausea, abdominal pain, diarrhea, headache and dizziness are the common ones at low oral doses. The approved intravenous product also lists low potassium and magnesium, muscle jerks and seizure-like episodes. In people with G6PD deficiency it can destroy red blood cells. The serious risk is serotonin syndrome — agitation, racing heart, high temperature, muscle rigidity — when combined with antidepressants, certain opioids or other serotonergic drugs; the approved product carries a boxed warning for it and some reported cases were fatal. It can also give falsely low readings on a pulse oximeter.

• ProvayBlue (methylene blue) injection prescribing information, DailyMed, revised 2/2024 — boxed warning, indication, contraindications, warnings and adverse reactions
• Ginimuge PR, Jyothi SD. Methylene blue: revisited. Journal of Anaesthesiology Clinical Pharmacology, 2010;26(4):517–520 — pharmacology and mechanism review

Complete safety information is provided during your visit and with every prescription. This page is a summary, not a substitute for your provider's advice.