Vitamin B12 test results vary significantly by age and ethnicity, according to a 2026 study of 61,193 blood samples from a London hospital. Black adults showed 34.6% lower rates of B12 deficiency markers compared to White adults, while Asian adults fell in between. These findings suggest doctors need age- and ethnicity-specific reference ranges rather than using the same standards for everyone.
A major study of over 61,000 blood samples from a diverse London hospital found that vitamin B12 test results vary significantly based on a person’s age and ethnic background. Researchers discovered that Black adults tend to have higher B12 marker levels and lower deficiency indicators than White adults, while Asian adults fall in between. These findings suggest that doctors may need different reference ranges for different populations when diagnosing B12 deficiency, rather than using one-size-fits-all numbers. According to Gram Research analysis, this discovery could help prevent both missed diagnoses and unnecessary treatments.
Key Statistics
A 2026 analysis of 61,193 blood samples from a London hospital found that Black adults were 34.6% less likely to show B12 deficiency markers compared to White adults, suggesting ethnic differences in B12 metabolism or status.
According to research reviewed by Gram, ethnic differences in B12 markers were minimal in children but became apparent in adulthood, with Black patients showing the highest active B12 concentrations and White patients the lowest.
A 2026 study of 12,233 patients found that B12 deficiency prevalence ranged from 7.8% to 2.4% depending on which testing threshold was used, demonstrating that current diagnostic standards may not be optimal for any population.
Research from a London hospital showed that adults over 65 years required higher MMA levels to be considered B12 deficient compared to younger adults under 65 years, indicating age-related changes in B12 metabolism.
The Quick Take
- What they studied: How vitamin B12 test results differ between age groups and ethnic backgrounds, and whether current testing standards work equally well for everyone.
- Who participated: Over 61,000 blood samples from patients at a London hospital between January 2022 and October 2023, representing diverse ethnic groups including White, Black, and Asian populations of all ages.
- Key finding: Vitamin B12 markers vary significantly by ethnicity and age. Black adults showed higher active B12 levels and lower deficiency markers compared to White adults, while children showed minimal ethnic differences.
- What it means for you: Your B12 test results should be interpreted differently depending on your age and ethnic background. Current standard reference ranges may not be accurate for all populations, potentially leading to missed diagnoses in some groups and unnecessary treatment in others.
The Research Details
Researchers analyzed blood samples from 61,193 patients at a London hospital over nearly two years. They measured two key B12 markers: holoTC (active B12) and MMA (methylmalonic acid), which is a backup test used when B12 results are unclear. The team compared results across different age groups and ethnic backgrounds to see if the patterns were consistent. For a subset of 12,233 patients with borderline B12 levels, they looked at both markers together to understand how well current testing standards work for different populations.
Current B12 testing uses the same reference ranges for everyone, regardless of age or ethnicity. If these ranges don’t actually apply equally to all groups, some people could be incorrectly diagnosed as deficient when they’re fine, or miss a real deficiency. This study helps doctors understand whether they need population-specific guidelines to test B12 accurately.
This study is strong because it used a very large sample size (over 61,000 samples) from a real hospital population, making results more representative of actual patients. The diverse ethnic makeup of London’s population provided good representation across groups. However, the study was observational, meaning researchers looked at existing data rather than randomly assigning people to different conditions. The findings are from one hospital system, so results may differ in other geographic areas.
What the Results Show
The study found clear ethnic differences in B12 markers, but only in adults. Children showed similar B12 levels regardless of ethnicity, suggesting these differences develop over time. Black adults had the highest active B12 levels, White adults had the lowest, and Asian adults fell in the middle. When researchers looked at MMA (the backup deficiency marker), Black adults were 34.6% less likely to show signs of B12 deficiency compared to White adults. This pattern held true even when using different cutoff values to define deficiency. The overall prevalence of B12 deficiency in the entire group was either 7.8% or 2.4%, depending on which testing threshold doctors used, highlighting how sensitive these results are to the standards applied.
Age also significantly affected B12 markers. Older adults (over 65 years) needed higher MMA levels to be considered deficient compared to younger adults (under 65 years), suggesting that B12 metabolism may change with age. The study found that using different MMA cutoff values dramatically changed how many people were diagnosed as deficient: a stricter cutoff identified 7.8% of the population as deficient, while a looser cutoff found only 2.4%. This variation demonstrates that current testing standards may not be optimal for any population.
Earlier research showed that standard B12 levels vary by ethnicity, but this is the first large study to examine how ethnicity affects the more specific active B12 marker (holoTC) and the backup deficiency test (MMA). Previous studies suggested ethnic differences existed but didn’t have enough data to establish clear patterns. This research confirms and expands those findings with a much larger, more diverse population, providing stronger evidence that one-size-fits-all reference ranges may not work.
The study was conducted in London, so results may not apply to other geographic regions or populations. The research looked at existing hospital data rather than following people over time, so researchers couldn’t determine whether ethnic differences in B12 markers actually affect health outcomes. The study couldn’t explain why these ethnic differences exist, whether from genetic factors, dietary patterns, or other causes. Additionally, the study didn’t include information about patients’ diets, supplements, or medical conditions that might influence B12 levels.
The Bottom Line
If you’re having B12 testing, discuss your results with your doctor in the context of your age and ethnic background. Don’t assume that standard reference ranges apply equally to you. If you’re experiencing symptoms of B12 deficiency (fatigue, numbness, memory problems), ask your doctor to consider your individual characteristics when interpreting results. Healthcare providers should consider using age- and ethnicity-specific reference ranges when available, rather than universal cutoffs. Confidence level: Moderate to High, based on a large sample size, though more research is needed to confirm optimal reference ranges.
Anyone getting B12 testing should know about these findings, especially Black and Asian adults whose results may be misinterpreted using current standard ranges. Healthcare providers, particularly those serving diverse populations, should be aware that current testing standards may not work equally well for all ethnic groups. People over 65 should know that B12 interpretation may differ from younger adults.
If you’re deficient in B12, supplementation typically begins improving symptoms within 2 to 4 weeks, with full recovery taking several months. However, the key benefit of this research is improving diagnostic accuracy now, not waiting for treatment effects.
Frequently Asked Questions
Does ethnicity affect vitamin B12 test results?
Yes, significantly. A 2026 study of 61,193 samples found Black adults had higher B12 markers and 34.6% lower deficiency rates than White adults. Ethnic differences were minimal in children but became apparent in adulthood, suggesting doctors should consider ethnicity when interpreting B12 tests.
What are holoTC and MMA and why do doctors use both?
HoloTC is active B12, the form your body can actually use. MMA is a backup test that rises when B12 is truly deficient. Doctors use both because holoTC alone can be unclear, especially in borderline cases. Together they provide a more accurate picture of B12 status.
Should my B12 reference range be different because of my age?
Possibly. Research shows adults over 65 have different B12 metabolism than younger adults, requiring different interpretation standards. Ask your doctor whether your age was considered when interpreting your results, especially if you’re over 65 or under 18.
How common is B12 deficiency according to this study?
It depends on the testing standard used. The 2026 study found B12 deficiency in either 7.8% or 2.4% of the population, depending on which MMA cutoff value doctors applied, showing how sensitive diagnosis is to the standards chosen.
Why do Black adults have different B12 markers than White adults?
The study didn’t determine the cause. Differences could stem from genetic factors, dietary patterns, medication use, or how different populations absorb and metabolize B12. More research is needed to understand the underlying reasons.
Want to Apply This Research?
- Log your B12 test results along with your age and ethnic background. Track any symptoms like fatigue, numbness, or brain fog before and after testing to help your doctor interpret results in context.
- If your B12 levels are borderline, ask your doctor specifically whether your age and ethnicity were considered when interpreting your results. Request a follow-up MMA test if your holoTC result is unclear.
- If you have low B12, track energy levels and neurological symptoms weekly using the app. Retest B12 levels every 3 to 6 months initially, then annually once stable. Note any dietary changes or new supplements that might affect B12 absorption.
This research provides important context for B12 testing but should not replace medical advice. B12 test interpretation is complex and depends on individual factors beyond age and ethnicity, including diet, medications, absorption issues, and medical history. Always discuss your B12 results with your healthcare provider before making any decisions about supplementation or treatment. If you suspect B12 deficiency, consult a doctor for proper evaluation and diagnosis. This article summarizes research findings and does not constitute medical advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.