NOW’s Testing of Methyl B-12 Brands on Amazon

Reveals Fewer Product Failings, But Underscores the Need for More Robust Testing and Quality Control Measures

NOW continued its award-winning quality testing program with a survey of 25 different brand samples of Methyl B-12 purchased on Amazon in January 2025.  Methyl B-12 was chosen for evaluation due to its high cost and the potential failure of its potency label claim. The results once again identified brands not meeting label claims, but fewer than other expensive supplements NOW has tested in the past.

This round of testing also highlighted that because of the inherent complexity of testing Vitamin B-12 across different matrices and dosage forms and the analyte’s instability, even reputable third-party labs may not be able to produce consistent test results. NOW recommends that this material therefore become a priority for collaboration by testing proficiency expert groups.

NOW purchased two bottles of each brand of Methyl B-12 supplement (plus two NOW products) to perform internal testing in NOW’s labs and cross-reference the results with a reputable external laboratory. However, we encountered significant inconsistencies from the external lab indicating a lack of clarity in test methods so chose not to publish those results. The following data reflect NOW’s internal analysis.

Understanding Methylcobalamin

Methylcobalamin is a highly bioavailable form of Vitamin B-12. Other common forms include Cyanocobalamin and Adenosylcobalamin (Dibencozide). Since Vitamin B-12 is nearly absent in plant-based foods, it is often supplemented by vegetarians. Methylcobalamin is preferred for solid dose supplements due to its stability and immediate usability by the body, while Cyanocobalamin is more stable in liquid forms but requires conversion to an active form within the body.

Testing Methodology

All samples were analyzed using High-Performance Liquid Chromatography (HPLC) at NOW’s laboratories, following a validated method aligned with the USP monograph for Methylcobalamin. However, due to the inherent instability of Vitamin B-12 and the difficulty contract labs face in maintaining stable standards and accurate analyte recovery, results may vary across different testing environments.  Below are our key observations:

1. NOW Products Performance:
   • Both NOW products tested well above the label claim at 140% and 114%. This is due to intentional overages to ensure full potency at best by date.
      
2. Market Performance:
   • Among the remaining 23 brands, results were highly variable:
     • 11 brands exceeded their label claim, with six testing over 120%.
     • 12 brands tested below 100%, with three showing potency between 90-100%, while three brands contained only 0-1% potency.
        
3. Repeat Low Performers:
   • Monohar, a brand from India, consistently failed, showing 0% potency in this round and during our SAM-e testing in November 2024.
   • aSquared showed some improvement but only reached 56% potency in its liquid product.
      
4. Challenges with Dosage Forms:
   • Liquid and gummy forms were less stable and harder to analyze accurately compared to tablets and capsules. Only one product met potency regulations, while others ranged from 1% to 105%.

Conclusion

Testing Vitamin B-12 is inherently challenging due to the instability of Methylcobalamin and the difficulty in obtaining consistent results across various matrices and dosage forms. Contract laboratories often struggle with maintaining standard stability and accurate analyte recovery, contributing to the variability observed in this study. Our internal data highlight the industry's need for more robust testing methods and quality control measures.