# Methylene blue appearance troubleshooting chart

Read from observation to evidence needed. This chart documents an investigation; it does not certify a bottle's safety, purity, strength, or expiry.

| Observable appearance | Possible explanation to investigate | What appearance cannot establish | Useful next evidence |
|---|---|---|---|
| Very dark center with a more visibly blue edge | Longer optical path through the center; concentration also affects absorption | Exact strength or freedom from impurities | Labeled concentration and an appropriate validated assay |
| Green cast that varies with lighting or background | Illumination, tinted packaging, and viewing conditions | Chemical identity or acceptable quality | Manufacturer appearance specification and consistent photographs |
| Persistent hue difference from the stated appearance | Formulation difference or chemical change | Which ingredient or reaction caused it | Ingredient list, lot records, and suitable analytical testing |
| Haze, floating material, or sediment | Bubbles, suspended particles, or precipitation, depending on formulation | Particle identity or microbial condition | Manufacturer investigation; particulate or microbiological testing where relevant |
| Fading or another change during storage | Redox chemistry or degradation among the possibilities | Potency, expiry extension, or successful restoration | Storage history and product-specific stability evidence |

## Observation record

1. Exact product and concentration:
2. Lot and expiry:
3. Appearance and date first observed:
4. Known storage or transport events:
5. Manufacturer response and supporting documentation:

Keep unexpected changes available for investigation. Do not alter the contents to improve their appearance.

## Supporting references

1. [Methylene blue aggregation study](https://pmc.ncbi.nlm.nih.gov/articles/PMC7689667/): concentration, solution conditions, and absorption.
2. [NIST color and appearance](https://www.nist.gov/publications/chapter-10-color-and-appearance): viewing conditions.
3. [USGS turbidity](https://www.usgs.gov/labs/national-water-quality-laboratory/science/science-topics/turbidity): scattering, colored constituents, and bubbles.
4. [Hikma injectable label](https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=4f222ee5-df03-46d5-a060-c63565b7186f): one formulation's defined appearance and storage requirements.

Source article: /en/articles/methylene-blue-green-cloudy-black/