Tools
Methylene blue grade checker
Methylene blue is sold in wildly different grades - pharmaceutical (USP), research chemical, and aquarium or industrial. Only the pharmaceutical grade is made to a purity standard fit for a human body. Answer three questions to see which one you likely have.
Reviewed 2026-08-21 · 4 sources
Three questions about your product
Does the label or Certificate of Analysis say USP, BP, EP, or pharmaceutical grade?
Does it say 'research use only', 'not for human consumption', or 'reagent grade'?
Is it sold as an aquarium, pond, or industrial / textile product?
Answer the questions above to see which grade you likely have. When in doubt, the honest default is: do not ingest it until you can confirm USP or pharmaceutical grade with a Certificate of Analysis.
This is an educational guide based on how a product is labeled and sold, not a lab test of what is in your bottle. It cannot detect contaminants. Only pharmaceutical (USP) grade is made to a purity standard fit for human use - verify with a Certificate of Analysis and a licensed provider.
The three grades, side by side
USP / pharmaceutical grade
Safe to ingestThe only grade made to a purity standard fit for a human body.
- Purity
- 97.0 to 103.0% methylene blue (the USP monograph standard)
- Made for
- Human pharmaceutical use - the grade FDA-approved products are made from
How to spot it
- -Label or Certificate of Analysis says USP, BP, EP, or pharmaceutical grade
- -Comes with a Certificate of Analysis (COA) showing purity
- -Sold by a pharmacy or for pharmaceutical compounding
Research chemical / reagent grade
Not for ingestionPurity is the seller's word, not a regulated standard, and it is sold explicitly not for people.
- Purity
- Vendor-claimed (often 98%+), self-reported and not independently verified against a pharmacopeia
- Made for
- Laboratory or research use
How to spot it
- -Says 'research use only', 'not for human consumption', or 'RUO'
- -Says 'reagent grade' or 'lab grade'
- -No USP / BP / EP pharmacopeia reference on the label or COA
Aquarium / industrial grade
Not for ingestionMade for tanks and textiles, not bodies. Do not ingest.
- Purity
- Variable and undocumented; vendors and manufacturers describe possible heavy-metal and process contaminants (community-level claims, not independently lab-verified)
- Made for
- Aquarium and pond treatment, textile dye, industrial processes
How to spot it
- -Sold as a fish-tank, pond, or aquarium treatment
- -Sold as a textile or industrial dye
- -Very cheap, large volumes, no purity documentation
Why the grade matters
Only one number here is a real, regulated standard: the USP monograph requires pharmaceutical methylene blue to be 97.0 to 103.0% pure, and FDA-approved products are made to it. Everything else is softer. "Research chemical" purity is self-reported by the seller, and the specific contamination claims made about aquarium and industrial grades come from vendors and manufacturers, not independent lab testing - which is exactly why this checker will not quote you a contaminant number it cannot stand behind. The safe rule does not need those numbers: if it is not labeled pharmaceutical or USP grade and backed by a Certificate of Analysis, do not put it in your body.
Sources
- [1]USP-NF Methylene Blue monographregulatoryDefines USP / pharmaceutical grade: 97.0 to 103.0% methylene blue on a dried basis.
- [2]PROVAYBLUE (methylene blue) injection - FDA label (DailyMed)labelFDA-approved methylene blue products are manufactured to the USP pharmaceutical standard.
- [3]WinAging - Heavy metals in reagent vs USP grade methylene blue (community)communityCommunity-level claims that non-USP grades can carry heavy-metal contamination - directionally consistent with vendor guidance, not independent lab testing.
- [4]APC Pure - What is USP Grade? A Methylene Blue 1% Case Study (community)communityVendor description of the USP grade testing criteria (identity, potency, purity, performance) and an example assay spec.