How to Read a Methylene Blue Certificate of Analysis (And Why It Matters)

By NooBlue Editorial

A methylene blue COA is the lab report behind a purity claim. It tells you which lab tested which sample, what they measured, how they measured it and what they found. Reading one takes about a minute once you know where to look: the lot number, the test methods, the specification column, the result column and the fine print at the bottom that says what the report does not cover. This guide walks through each part, then reads a real certificate, our own, line by line, including what it leaves out.

NooBlue sells methylene blue capsules, gummies and drops, so we have a stake in how people judge testing. We use our own report as the worked example because we can show it in full and explain its limits honestly. Competitor and lab-supplier documents quoted here were read in September 2026 and are linked in the sources.

What Is a Methylene Blue Certificate of Analysis?

A certificate of analysis is a document issued by a testing laboratory that records the results of specific tests on a specific sample. For methylene blue, that usually means an identity test (is this methylene blue?), sometimes an assay or purity figure (how much of it is methylene blue?), and often a heavy-metals panel. Better reports add microbial testing and, for finished products, the amount of methylene blue per capsule, gummy or milliliter.

The key word is sample. A COA describes the material that was sent to the lab, tied to a lot or batch number. Most labs print a line saying exactly that. Our own certificate from Contract Testing Laboratories of America (CTLA) says the report “represents data for the sample submitted and does not constitute a guarantee of quality for the entire product from which it was taken.” That sentence is standard, and it is the right way to think about any COA: it is evidence about one lot, not a promise about every bottle.

Testing can be done in-house by the manufacturer or by an outside laboratory. An outside lab has less reason to shade results, which is why brands point to third-party testing. It still matters what was tested. An outside lab’s report on a raw powder tells you about the powder, not about the capsule made from it months later.

How to Read a Methylene Blue COA, Line by Line

Most COAs share the same layout: a header describing the sample, a results table, and a footer with signatures and fine print. Here is what each part tells you.

The header

• Laboratory name and report number. A named lab with a report ID means you can, at least in principle, confirm the document with the lab.
• Sample name. What the brand called the sample when it sent it. Check that it plausibly matches the product or ingredient you are being shown.
• Lot or batch number. The single most useful field. It ties the report to a production lot, and a careful brand will tell you which lot your bottle came from.
• Dates. When the lab received the sample and when it issued the report. A report that is years old may not describe the lot on sale today.

The results table

• Analysis. What was tested, such as methylene blue identity, arsenic or lead.
• Method. How it was tested. HPLC (high-performance liquid chromatography) separates the sample into its components and is used for identity and purity. USP <233> is the United States Pharmacopeia procedure for measuring elemental impurities such as lead and arsenic.
• MDL or LOQ. The method detection limit (or limit of quantitation), the smallest amount the method can reliably see. A result written as “<0.001” means below that limit.
• Specification. The target the result is judged against, such as “97.0% to 103.0%” or a maximum in ppm. A specification of “Report” means no pass or fail limit was applied. The lab simply measured and reported the value.
• Result. What the lab found. A number with units is the most informative. “Conforms” or “Pass” tells you the sample met the test’s criteria, not how much of the material is methylene blue.
• Units. Heavy metals are usually in ppm (parts per million), which is the same as micrograms per gram.

The footer

Look for a signature, a date and any scope statement. Phrases like “specifications provided by the customer” mean the brand, not the lab, chose which limits to apply, or chose to have values reported without limits. “For research use only” means the document describes a laboratory chemical, not a product made for people.

A Worked Example: Reading NooBlue’s CTLA Report

This is the certificate linked in the “Purity & testing” section of every NooBlue product page, for example our methylene blue drops. Here is what it says, field by field.

Now the limits, which matter as much as the results. The report covers the raw methylene blue ingredient, not a finished capsule, gummy or bottle of drops. It confirms identity but does not give a numerical purity percentage. The heavy-metal specifications say “Report”, so the values were measured without a pass or fail limit printed beside them. There is no microbial panel, and it is one lot, not a certificate for every batch. That is why our product pages describe it as ingredient-level evidence and tell you to read the original document alongside its scope.

To put the cadmium figure in context: 0.010 ppm means 0.010 micrograms of cadmium per gram of methylene blue. A 5 mg capsule holds 0.005 grams of methylene blue, so the ingredient in one capsule would carry about 0.00005 µg of cadmium at that level. You can run the same arithmetic on any COA: ppm times grams of ingredient per serving gives micrograms per serving.

What Purity Should Methylene Blue Have?

The reference point for supplement-grade methylene blue is the USP monograph. It states that methylene blue contains not less than 97.0% and not more than 103.0% of methylene blue (C₁₆H₁₈ClN₃S), calculated on the dried basis. Two words in that sentence trip people up.

“Dried basis.” Methylene blue powder holds water. The monograph lists anhydrous, monohydrate, trihydrate and pentahydrate forms, each with its own CAS number and molecular weight. Water adds weight without adding methylene blue, so the assay is calculated after accounting for that water. A purity figure quoted without its basis can’t be compared with the monograph range.

Assay vs HPLC purity. These are different numbers. HPLC purity usually reports how much of what the instrument detected was the main compound. An assay reports how much methylene blue is actually in the material. A lab-supplier reference standard we read from MedChemExpress shows the gap: its certificate lists 95.11% purity by HPLC, a 1.11% loss on drying, and an assay of 94.05% worked out from both. Same batch, three different figures.

Claims like “99.9% pure” or “99.99% pure” on a label are brand statements. They may be accurate, but ask which document shows the figure, which method produced it and on what basis. The monograph’s list of reference standards also includes USP Azure B RS next to the methylene blue standard, a sign that azure B, a closely related dye, is among the impurities the full monograph checks for. Our explainers on what methylene blue purity figures mean and USP-grade methylene blue go into the grades in more detail, and lab grade vs pharmaceutical grade methylene blue explains why the label wording differs.

Raw-Ingredient Reports vs Finished-Product Reports

This is the distinction most buyers miss, and it is worth being plain about. A raw-ingredient report tests the methylene blue powder before it becomes a product. A finished-product report tests the capsule, gummy or solution you actually take, and can confirm the amount per serving and check for microbes introduced during manufacturing.

Both are useful. A raw-ingredient report tells you the starting material was methylene blue and gives you a heavy-metal profile for that lot. A finished-product report tells you the label amount is in the product. When a brand shows you a certificate, ask which one it is. NooBlue’s published report is ingredient-level. Some brands go further, and Nutricel, for example, says the QR code on its label links to the certificate for that lot and that every batch is tested for identity, potency, heavy metals and microbes. If a brand calls a raw-ingredient report a finished-product or per-batch certificate, that is the mismatch to question. Our Nutricel vs NooBlue comparison sets the two approaches side by side.

Red Flags on a Methylene Blue COA

• No lot number. Without it, the report can’t be tied to anything you can buy.
• No laboratory name or report ID. A document with no issuer is hard to check.
• A specification presented as a result. “≥99%” in the result column is a target, not a measurement.
• Results with no units or no method. “Pass” beside “heavy metals” tells you very little. Look for each element, a number, ppm and a method such as USP <233>.
• A sample name that doesn’t match. A report for a different product or a generic “blue dye” sample is not evidence for the product in front of you.
• “For research use only” in the fine print. The document is real, but it describes a laboratory chemical.
• Claims the document doesn’t support. A label promising “99.9% pure, tested every batch” next to a single identity test is the clearest warning sign of all.

For a broader checklist that goes beyond paperwork, see how to test if methylene blue is real and how to find safe, authentic methylene blue supplements.

Why a Chemical Supplier’s COA Is a Different Document

Search for “methylene blue COA” and most results are certificates from laboratory chemical suppliers such as MedChemExpress, Sigma-Aldrich and Otto Chemie. These are genuine, lot-specific documents, often from labs that work to ISO/IEC 17025. They answer lab questions, though, not supplement questions.

Take two MedChemExpress certificates from the top of those results. Its methylene blue reference standard (batch 1096659, tested January 6, 2026) confirms identity by NMR and mass spectrometry, reports 95.11% HPLC purity against a specification of not less than 90.0%, and lists storage and expiry. Its methylene blue trihydrate (CAS 7220-79-3, batch 716729) reports 98.0% purity by NMR and carries the line “Product has not been fully validated for medical applications. For research use only.” Neither certificate reports heavy metals or microbes, because a researcher weighing out milligrams for an experiment doesn’t need them.

So if the only certificate a supplement brand can show you is a chemical supplier’s research-grade sheet, you are looking at a document written for a different purpose. It may still tell you the identity and purity of the powder. It won’t tell you about heavy metals, and it says nothing about the finished product. Methylene blue sold for fish tanks is a further step away. Our guides to aquarium-grade methylene blue and food-grade methylene blue explain those labels.

How to Ask a Brand for Its Methylene Blue COA

You can and should ask before you buy. A short email does the job:

1. Name the product and, if you already own it, the lot number printed on the bottle.
2. Ask whether the certificate is for the raw ingredient or the finished product.
3. Ask which laboratory ran the tests and which methods were used.
4. Ask whether the report includes a purity or assay figure, heavy metals with numbers, and microbial testing.

A good answer names the lab, matches the lot and says plainly what was and wasn’t tested. A vague answer, a refusal or a generic template with no lot number tells you something too. Our reviews of Meraki Blu, Biopharm and Blue Organics note what each brand shows, and our best methylene blue supplements guide applies the same checks across the market. For our own record, see is NooBlue legit?

Before You Take Methylene Blue

A clean certificate does not make methylene blue right for everyone. These warnings match the “Safety: read before use” box on the NooBlue capsules product page:

• Do not take methylene blue if you take an SSRI, SNRI, MAOI or any other serotonergic medicine, including many antidepressants. Methylene blue is a potent reversible inhibitor of MAO-A (Ramsay 2007), and the combination can cause serotonin syndrome.
• Do not take it if you have G6PD deficiency.
• Do not take it if you are pregnant or breastfeeding, and it is not for anyone under 18.
• Talk to your doctor first if you take any prescription medicine or have a kidney or liver condition.
• Methylene blue can turn urine blue or green, which is expected. Do not exceed the suggested serving: one 5 mg capsule a day, one 10 mg gummy a day, or 10 drops (5 mg) of the 1% solution.

Our guides to what not to take with methylene blue, who should not take methylene blue and methylene blue side effects cover each point, and how many mg of methylene blue per day explains serving sizes across formats.

Frequently Asked Questions

What is a COA for methylene blue?

It is a certificate of analysis: a lab report on one sample from one lot of methylene blue. It lists the tests run (identity, purity or assay, heavy metals, sometimes microbes), the methods, the specifications and the results. It describes the sample that was tested, not every bottle ever made.

What purity percentage should methylene blue be for human use?

The USP monograph requires 97.0% to 103.0% methylene blue, calculated on the dried basis. When you see a purity figure, check the method and the basis. An HPLC purity number and an assay number measure different things, and a figure that ignores water content can’t be compared with the monograph range.

What does “Conforms” mean on a methylene blue COA?

It means the sample met the criteria of that test. On an identity test, “Conforms” means the lab identified the sample as methylene blue. It does not tell you what percentage of the material is methylene blue. For that you need an assay or purity result with a number.

Is a COA from the raw ingredient supplier enough?

It is useful but limited. A raw-ingredient report confirms the identity of the starting powder and, if it includes heavy metals, gives you that lot’s metal profile. It doesn’t confirm how much methylene blue ended up in each capsule or bottle, or whether anything was introduced during manufacturing. NooBlue’s published CTLA report is ingredient-level, and we describe it that way.

Can you ask a company for its COA before buying?

Yes, and it is reasonable to do so with any methylene blue product. Ask for the certificate that matches the lot on sale, whether it covers the ingredient or the finished product, and which lab issued it.

Is methylene blue USP certified?

Not in the way the phrase suggests. USP is a standards organization that publishes the methylene blue monograph. “USP grade” means the material is described as meeting that monograph. The way to see whether it does is a certificate showing the monograph tests and their results.

What is the CAS number for methylene blue?

Anhydrous methylene blue is CAS 61-73-4. The USP monograph also lists 7220-79-3 for the trihydrate, 67183-68-0 for the monohydrate, 32680-41-4 for the pentahydrate and 122965-43-9 for the hydrate in general. A COA should name the form it describes.

Why don’t doctors recommend methylene blue?

In medicine, methylene blue is mainly a hospital drug given by injection under monitoring for specific acute problems. For everyday focus and energy there are no large long-term trials in healthy people, so there is no standard dose for a doctor to recommend. It also interacts with many common antidepressants, which makes doctors cautious. We cover this in why don’t doctors prescribe methylene blue.

The Bottom Line

A methylene blue COA is only as useful as your reading of it. Find the lab, the lot and the dates. Check whether the result column holds numbers or just “Conforms”. Look for heavy metals with units and a method. Then ask the question most people skip: is this the raw ingredient or the product I am buying? We publish our CTLA ingredient report on every product page with that scope written beside it, and our capsules, gummies and drops all use methylene blue USP. You can compare the three formats below or in the NooBlue shop.

Sources

1. USP-NF. Methylene Blue monograph (definition, CAS numbers and reference standards). doi.usp.org
2. Contract Testing Laboratories of America. Certificate of Analysis, CTLA ID 135621, lot 2025022801, shown on the NooBlue product pages. nooblue.com
3. MedChemExpress. Certificate of Analysis, Methylene Blue (Standard), HY-14536R, batch 1096659 (read September 2026). medchemexpress.com
4. MedChemExpress. Certificate of Analysis, Methylene blue (trihydrate), HY-B1359, batch 716729 (read September 2026). medchemexpress.com
5. Nutricel. Blue Liquid 1% methylene blue solution product page (checked September 2026). nutricel.store
6. Ramsay RR, Dunford C, Gillman PK. Methylene blue and serotonin toxicity: inhibition of monoamine oxidase A (MAO A) confirms a theoretical prediction. British Journal of Pharmacology. 2007;152(6):946-951. PubMed 17721552
7. Ostrovsky A, Afzal M. Methylene Blue. StatPearls. Updated January 2, 2026. NCBI Bookshelf NBK557593