Now survey of vitamin B12 brands reveals unsubstantiated potency claims

Supplement brand Now’s latest quality testing program flags discrepancies between methyl B12 potency claims and actual levels in the supplement, having surveyed 25 different brand samples purchased on Amazon in January. Notably, 11 brands exceeded their label claim of potency, with six testing over 120%.

Additionally, 12 brands tested below 100%, with three showing potency between 90–100%, while three brands contained only 0–1% potency.

Methyl B12 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,” a spokesperson for Now reveals.

Inherent complexity of vitamin B12 testing

Now, which markets its own B12 supplements, claims this round of testing shows that even reputable third-party labs may not produce consistent test results. Testing vitamin B12 is inherently challenging due to the instability of methylcobalamin and the difficulty in obtaining consistent results across various matrices and dosage forms.

The brand urges greater priority for this essential nutrient in terms of testing in collaboration with proficiency expert groups.

Now purchased two bottles of each brand of Methyl B12 supplement, plus two Now products, to perform internal testing in its 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 we chose not to publish those results. The following data reflect Now’s internal analysis,” the brand elaborates.

Understanding methylcobalamin

Methylcobalamin is a highly bioavailable form of vitamin B12. Other common forms include cyanocobalamin and adenosylcobalamin (dibencozide). Since vitamin B12 is nearly absent in plant-based foods, vegetarians often supplement it.

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.

All samples were analyzed using high-performance liquid chromatography at Now’s laboratories, following a validated method aligned with the US Pharmacopoeia monograph for methylcobalamin.

“However, due to the inherent instability of vitamin B12 and the difficulty contract labs face in maintaining stable standards and accurate analyte recovery, results may vary across different testing environments,” says the brand.

The survey found 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,” highlights the brand.

Among the remaining 23 brands, Now pinpoints “repeat low performers”: Monohar, a brand from India, consistently failed, showing 0% potency in this round and during Now’s SAM-e testing in November 2024.

Another brand, aSquared, showed some improvement but only reached 56% potency in its liquid product.

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%.

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.

Vitamin B12 in focus

Vitamin B12 consumption was recently in the spotlight, as a recent paper uncovered that current recommended levels of vitamin B12 may be too low to counter the cognitive decline that comes with aging.

In previous research, scientists identified a link between vitamin B12 supplementation and improved outcomes in multiple sclerosis treatment.

Meanwhile, an international research team developed a method of producing carbon-neutral spirulina containing biologically active vitamin B12 in levels “comparable to beef,” offering a viable plant-based source for the essential nutrient.