What USP means, why most products fail, and how to check one yourself.

• USP grade is the one made for people. Industrial, laboratory, and aquarium grades are not made to be swallowed and can carry heavy metals.
• USP grade describes the raw material. It is not a certification of the finished product or an FDA approval, so look for a lab report too.
• 39 of the 62 products we tested failed. Nutricel funded the testing, and the results reflect the units and lots we bought.

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.

Methylene blue is made in several grades. Industrial grade is for dyeing. Laboratory grade is for stains. Aquarium grade is for fish tanks. None of these is made to be swallowed, and they can carry heavy metals and other contaminants.^[18]

USP grade means the raw material meets the United States Pharmacopeia standard for identity, purity, and contaminants. It is the grade made for people.

The grade is the single most important word on a methylene blue label.

USP grade describes the raw material. It does not mean USP tested or certified the finished product, and it is not an FDA approval.^[18]

A brand can buy USP grade material and still make a bad product if it mixes it wrong, uses too little, or adds contaminated fillers. That is why the grade alone is not enough.

The next step is a lab report on the finished product.

Methylene blue is often made with metal catalysts. Poorly purified material can carry traces of metals such as lead, arsenic, and cadmium, which is one of the main things the USP standard limits.^[18]

Finished-product lab reports usually include a heavy metals panel. If a brand does not publish one, you have no way to know.

Our capsules are third-party tested, and the lab reports are on our site where you can open them.

Our lab reports →

Open a capsule into a clear glass of water. Real methylene blue turns the water a deep midnight blue within seconds. Ingredients like cacao may settle while the blue stays vibrant.^[16]

A pale blue, gray, or brown tint can mean there is little methylene blue in the product, or none at all.

Color is not a laboratory test, but it is a useful first check, and it costs nothing.

We bought methylene blue products from other brands and tested them with a water test, a lab test, or both. As of October 8, 2026, 39 of the 62 products we tested failed.^[16]

We fund the testing ourselves, and the results reflect the specific units and lots we bought. You can search every result in our database.

We sell methylene blue, so you should check us too. That is why our own reports are public.

Search the database →

Our methylene blue is USP grade, tested at 99.4% purity, and our capsules are made in an NSF GMP verified facility in the United States from domestic and imported ingredients.

Our capsules are third-party tested, and the reports are on our certifications page.

If anything on a report does not make sense to you, ask us. We would rather explain it than have you guess.

Certifications →

The grade on the label is the first check and a lab report on the finished product is the second. A glass of water gives you a quick third check at home.

• USP sets limits on heavy metals such as lead, arsenic, and cadmium.
• A brand can buy USP grade material and still make a poor product.
• Real methylene blue turns water deep midnight blue within seconds. Pale blue, gray, or brown is a red flag.
• Every result from our testing is searchable in our database.
• Our methylene blue is USP grade, tested at 99.4% purity, and made in an NSF GMP verified facility in the United States.

Clinical and regulatory

Nutricel testing and data