Tools
Methylene blue grade checker
By An NayalLast reviewed 4 sources
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.
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.
Worked example
The checker opens with no answers and shows nothing until it has enough to go on. Take a bottle bought online whose label reads "USP grade" and, in smaller print, "for research use only".
- Answer Yes to the first question (USP, BP, EP or pharmaceutical grade). One Yes is enough for a verdict, so the card appears at once: "Fit for human use", USP / pharmaceutical grade.
- Answer Yes to the second question (research use only, not for human consumption, or reagent grade). The card changes to "Not verified for human use", research chemical / reagent grade, because that red flag outranks the USP claim.
- Answer No to the third question (aquarium, pond or industrial). The verdict stays research grade. A Yes here would have changed it to "Do not ingest", aquarium / industrial grade.
If you answer No to all three, the checker shows "Grade not confirmed" under a caution heading. Nothing you told it points to pharmaceutical grade, so it does not assume the product is fit to ingest. Tapping an answer you already picked clears it, so you can change your mind as you read the label.
How the checker decides
The checker is a short list of rules applied in a fixed order. It checks the most disqualifying signal first and stops at the first match.
1. sold for aquarium, pond or industrial use -> aquarium / industrial grade
2. research use only / not for human consumption -> research grade
3. says USP or pharmaceutical -> USP grade
4. none of the above -> grade not confirmed
The order is the point. A product only lands on USP grade when it is positively labeled pharmaceutical and carries none of the red flags, so a USP claim cannot outweigh a "not for human consumption" warning on the same bottle.
The checker shows a verdict as soon as any answer is Yes, because a single Yes already decides a rule. With only No answers it waits until all three are answered, since an unanswered question could still be a red flag. It never quotes a contaminant figure for the lower grades: those claims come from vendors and manufacturers, not independent lab testing, so the checker keys off label cues you can check yourself and defaults to caution.
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.
Questions people ask
What does USP grade mean for methylene blue?
It means the product meets the USP monograph for methylene blue, which requires 97.0 to 103.0% purity. FDA-approved methylene blue products are made to that standard. It is the only grade on this page with a regulated purity figure.
Is aquarium methylene blue safe to ingest?
No. The checker classes anything sold as an aquarium, pond, or industrial or textile product as "Do not ingest". It is made for tanks and textiles, and its purity is undocumented.
My bottle says USP but also 'research use only'. Which is it?
The checker returns research grade. It checks the red flags before the USP claim, so a product labeled 'not for human consumption' or 'research use only' is never classed as pharmaceutical, whatever else the label says.
Can this checker tell what is in my bottle?
No. It reads how a product is labeled and sold, not what is inside it, so it cannot detect contaminants. A Certificate of Analysis showing USP purity is the paperwork to ask for.
Pepteca is for education and information only. It does not provide medical advice, diagnosis, or treatment, and its calculators perform unit math only. Always verify with a licensed provider before starting, changing, or stopping any protocol. Many peptides are not approved for human use and may be regulated differently where you live.