How it is absorbed, where it goes, how long it stays, and why your urine changes color.

• Most of an oral dose reached the blood in one study. Peter and colleagues measured roughly 72 percent in 2000. Treat that as a ballpark.
• Most of a dose clears within the first day. The main half-life is several hours. The FDA label lists a terminal half-life of about a day.
• Blue-green urine is expected. It is harmless and temporary, and it fades a day or two after you stop.

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.

When you swallow methylene blue, it is absorbed through the gut into the bloodstream. Peter and colleagues compared oral and IV methylene blue in healthy volunteers in 2000 and found that a large share of the oral amount reached the blood, roughly 72 percent in their measurements.^[6]

Food, the form you take, and individual differences can all shift that number, so treat it as a ballpark from one study rather than a promise.

From the blood it spreads into tissues, including the brain, before the body starts clearing it.

Half-life is the time it takes for half of something to leave the blood. Peter and colleagues measured a half-life of several hours for methylene blue after a single dose. The FDA label for Provayblue lists a longer terminal half-life, about a day, because it tracks the very last traces.^[6,1]

Both numbers are true. Most of a dose clears within the first day, and small traces linger longer.

That is why people who take it in the morning often report it is out of the way by the evening, and why the color in urine fades over a day or two after stopping.

Part of each dose leaves the body through the kidneys. Peter and colleagues measured both the blue form and the colorless form in urine. When the colorless form meets air, it turns blue again, which is why the color can deepen after you go.^[6,1]

Depending on how much you take and how much water you drink, urine can look blue, green, or teal. The FDA label lists blue-green urine as one of the most common effects.

It is harmless and temporary. We tell every customer to expect it so nobody gets a surprise on day one.

Liquid methylene blue can tint your tongue and teeth for a little while, which is one reason many people prefer capsules. Stool can also look greenish.^[1]

At hospital amounts, the FDA label lists skin discoloration as a possible effect. At supplement amounts that is rarely reported, but it shows what happens when the amount climbs.

If you take the liquid, rinse your mouth after and keep it away from clothes and countertops. It stains almost everything it touches.

The body clears methylene blue mainly through urine, with some through bile into stool. Peter and colleagues tracked both routes.^[6,1]

Because the kidneys do much of the work, anyone with kidney problems should talk to a doctor first. The FDA label also calls for extra caution in people with severe kidney impairment.

Drinking water does not change what the compound does, but it does dilute the color you see.

Swallowed methylene blue moves from the gut into the blood, spreads into tissues including the brain, and leaves mostly through the kidneys. The color changes you may notice happen along the way.

• Food, the form you take, and individual differences can all change how much is absorbed.
• The colorless form in urine turns blue again when it meets air.
• Liquid can briefly tint your tongue and teeth, and stool may look greenish.
• It leaves mainly through urine, with some through bile into stool.
• If you have kidney problems, talk to a doctor first. The FDA label calls for extra caution with severe kidney impairment.

Clinical and regulatory

Peer-reviewed research and history