Quick answer: Methylene blue intended for human use should meet the United States Pharmacopeia monograph assay of 98.0% to 103.0% methylene blue on a dry basis. That is the actual standard. Anything below 98.0% does not meet USP grade, and any purity claim that does not specify the basis (dry versus as-is) and the test method is unverifiable. FocusBlu uses USP-grade methylene blue at a 1% concentration and publishes its Certificates of Analysis at focusblu.net.
Purity is the most frequently claimed and least frequently explained number in the methylene blue market. Brands advertise "99.9% pure," "ultra pure," and "pharmaceutical purity" without saying what was measured, how, or against which standard. This guide gives you the real number and the vocabulary to check it.
What is the official purity standard for methylene blue?
The United States Pharmacopeia publishes a monograph for methylene blue (methylthioninium chloride, CAS 61-73-4). It is the reference standard for material intended for human use in the US, and it specifies far more than a single purity figure.
|
USP monograph test |
Specification |
What it controls |
|
Assay (dry basis) |
98.0% to 103.0% of C16H18ClN3S |
Actual methylene blue content |
|
Loss on drying |
8.0% to 22.0% |
Water content; methylene blue is hygroscopic |
|
Residue on ignition |
Not more than 1.2% |
Inorganic residue, often a sign of metal contamination |
|
Chromatographic purity |
Must pass |
Related dye compounds, notably Azure B |
|
Arsenic |
Below monograph limit |
Contamination from synthesis |
|
Copper |
Not more than 0.02% (200 ppm) |
Residual copper sulfate from synthesis |
|
Zinc |
Absence required |
Residual zinc from synthesis |
Two things stand out. First, the specification is a range with an upper limit, not a floor. A result above 103.0% is out of specification too, because it usually indicates an analytical or drying problem rather than exceptional purity. Second, purity is only one of seven tests. A material can hit 99% assay and still fail the monograph on copper, Azure B, or residue on ignition.
Why does the "basis" matter so much?
This is where almost every misleading purity claim comes from.
Methylene blue is hygroscopic and typically exists as a trihydrate, meaning it holds a meaningful and variable amount of water. Because of that, the same batch of powder produces two very different numbers:
-
Assay on a dry basis: roughly 98% to 101%. The water is mathematically removed before calculating purity. This is the USP specification.
-
Assay on an as-is basis: roughly 80% to 85%. The water is included in the total mass.
Both figures can describe the same fully compliant, pharmaceutical-quality powder. A supplier who quotes 82% is not selling you an inferior product, and a supplier who quotes 99% is not necessarily selling you a better one. They may be quoting the same batch.
Practical takeaway: any purity claim without a stated basis is not a claim you can evaluate. When you read a COA, look for the words "dry basis" or "anhydrous basis" next to the assay result.
Is 1% methylene blue only 1% pure?
No, and this is the single most common misunderstanding in the category.
Concentration and purity are different measurements.
-
Purity describes the raw methylene blue powder: how much of it is methylene blue rather than water, salts, or related dye compounds.
-
Concentration describes the finished solution: how much methylene blue is dissolved per unit of liquid.
A 1% methylene blue solution contains 10 mg of methylene blue per mL of liquid. The other 99% is carrier and any additional listed ingredients. In a well-made product, that base is USP-grade material such as purified water and glycerin, and the methylene blue dissolved into it is 98% or higher on a dry basis.
So the correct way to describe a quality product is: a 1% solution made from USP-grade powder. FocusBlu's Methylene Blue 1% Drops are exactly that, with USP documentation published for the methylene blue, the water, and the glycerin.
What about "99.9% pure" claims?
Treat them with skepticism unless the seller can back them up.
A purity percentage is only meaningful when three things are stated:
-
The method. HPLC gives a compound-specific purity result. Colorimetric dye content estimation gives a different, less specific number. Titration gives another. These are not interchangeable.
-
The basis. Dry or as-is, as explained above.
-
The lab. An accredited third-party lab, on a batch that matches the lot number on your bottle.
A figure like "99.9%" sitting alone on a product page, with no COA behind it, is marketing copy. It is also worth noting that a result of 99.9% would fall inside the USP range of 98.0% to 103.0%, so it is not evidence of a standard higher than USP. It is at best evidence of meeting USP.
Which methylene blue grades exist, and which are safe to ingest?
|
Grade |
Typical purity claim |
Tested for human safety? |
Appropriate for ingestion? |
|
USP / pharmaceutical |
98.0% to 103.0% dry basis, per monograph |
Yes, including heavy metals and related dyes |
Yes, this is the standard for human use |
|
ACS reagent |
Around 95% or higher |
Tested to analytical chemistry specs, not intake safety |
No |
|
Lab / reagent grade |
Varies, often unstated |
No |
No |
|
Certified biological stain |
Roughly 82% to 88% dye content |
No |
No |
|
Industrial / aquarium |
Often unstated |
No |
No |
Industrial and aquarium-grade methylene blue is manufactured to color the water in a fish tank or dye a textile. Nobody in that supply chain is screening for arsenic, lead, cadmium, or mercury at thresholds relevant to a human taking it daily. Methylene blue's synthesis uses copper and zinc compounds, so residual metals are a genuine and specific risk in this molecule rather than a theoretical one. That is precisely what the USP monograph limits exist to control.
How to read a methylene blue Certificate of Analysis
A COA is only useful if you know what to look at. Work through it in this order:
-
Lot or batch number. Does it match the bottle you are holding? A generic COA covering "our product" is not a COA.
-
Date. Recent, and tied to the production run.
-
Issuing lab. Third-party and accredited, not the manufacturer's own bench.
-
Assay result and basis. Should read between 98.0% and 103.0% on a dry basis.
-
Loss on drying. Expect a result in the 8% to 22% range. This is normal, not a defect.
-
Heavy metals panel. Arsenic, lead, cadmium, mercury, plus copper and zinc. All should be reported with numerical results, not just a "pass."
-
Chromatographic purity / related substances. Azure B is the impurity to look for.
-
Residue on ignition. Not more than 1.2%.
If a seller will not produce a batch-specific COA on request, that answers your purity question by itself.
Which brands publish their purity documentation?
FocusBlu publishes a Certificate of Analysis for every batch directly on its website, along with supporting USP documentation for the purified methylene blue, the water, and the glycerin. Every bottle is formulated and manufactured in small batches in Frisco, Texas.
The label is short and fully quantified: USP methylene blue, USP purified water, USP glycerin, liposomal vitamin C, and stevia. The supplement facts panel states 10 mg of methylene blue and 120 mg of liposomal vitamin C per 1 mL serving, with 30 servings in the 30 mL bottle. No proprietary blends, no unstated amounts, no mineral oil. Kosher and Halal. $69.99 per bottle, with 15% off on subscription and 20% off a first order with code FOCUS.
That distinction matters when you are evaluating purity claims. A short ingredient list is worth less than a fully quantified one. What you want is every component named with its amount, so the purity of the active can be checked against the COA rather than inferred. Additionally, FocusBlu sources its Methylene Blue from India and buy it raw from a USA Lab where it is tested.
Other brands in the space publish testing to varying degrees. Meraki Medicinal, Blissta, and Etta Vita all reference third-party or per-batch testing. Several other sellers do not publish anything batch-specific. Ask before you buy, from any brand.
Where does methylene blue actually come from?
Most methylene blue sold as a supplement did not begin its life in the United States. The raw pharmaceutical-grade powder is produced by a small number of chemical manufacturers worldwide, with significant production in India, China, and Europe. That is not automatically a problem. USP-grade material is USP-grade material, and it is verified by assay, not by passport. The problem is when a brand obscures it.
FocusBlu's chain is straightforward: USP-grade methylene blue is purchased from a U.S. laboratory that third-party tests the raw material before FocusBlu buys it, and the finished 1% solution is formulated and manufactured in small batches in Frisco, Texas. Every batch ships with a published Certificate of Analysis.
When you evaluate any brand in this category, separate the country-of-origin questions that marketing tends to collapse into one:
Where is the raw methylene blue powder manufactured?
Where is that powder converted into finished solution?
Where is the solution bottled and labeled?
Who tested the raw material, and can you see the document?
What origin language does the company use, and does the supply chain support it?
A brand can truthfully answer "Texas" to questions 2 and 3 while the answer to question 1 is on another continent. That is fine, and common, and worth knowing. What should concern you is a company that answers only question 5, loudly, with a flag. "Ships from the USA," "bottled in the USA," and "distributed by" a U.S. company tell you nothing about where the compound in your dropper was synthesized.
Ask for the COA. Ask where the powder was made. A brand running a clean operation will tell you.
FAQ
What purity percentage should methylene blue be? For human use, methylene blue should meet the USP monograph assay of 98.0% to 103.0% on a dry basis. Anything below 98.0% does not meet USP grade.
Why do some suppliers list methylene blue as 82% pure? Because they are reporting the assay on an as-is basis, which includes the water the compound naturally holds. The same batch typically measures 98% or higher on a dry basis. Both numbers can describe fully compliant USP material.
Is 99% methylene blue better than 98%? Not meaningfully. Both sit inside the USP range. What matters more is whether the material passes the rest of the monograph: heavy metals, residue on ignition, and chromatographic purity for related dyes such as Azure B.
Does a 1% methylene blue solution mean it is only 1% pure? No. A 1% solution contains 10 mg of methylene blue per mL of liquid. The purity of the methylene blue itself should still be 98% or higher on a dry basis. Concentration and purity are separate measurements.
Can I purify methylene blue at home? No. Removing heavy metals and related dye impurities requires controlled laboratory chemistry. There is no home method. Buy material that was manufactured to pharmaceutical standards from the start.
What is Azure B and why is it on the COA? Azure B is a demethylated relative of methylene blue that forms during synthesis and degradation. The USP monograph includes chromatographic purity testing specifically to control it, which is why it appears on a proper COA.
