Quick answer: Vitamin B12 is needed for nerve health, red blood cells, DNA and energy. Low B12 can cause fatigue, numbness or tingling, memory problems and anemia. Common causes include a plant-based diet, older age, acid-blocking medications, metformin and pernicious anemia. Borderline results may be clarified with MMA and homocysteine tests.
What is Vitamin B12?
Vitamin B12 (cobalamin) is a vitamin found in animal foods. It is needed for nerve insulation (myelin), red blood cell formation, DNA synthesis and methylation. This marker is part of the Healthspan Assessment panel available to my 1-on-1 patients.
Why Vitamin B12 matters
- Nerve and brain health
- Red blood cell production
- Energy metabolism
- Methylation and homocysteine processing
Understanding your result
Reference ranges vary by lab, age and sex. Your provider interprets your result against the lab’s range and your overall picture, rather than chasing a single number. Functional labs are optional. They can be helpful in more complex cases, and in my practice they are available only to patients working 1-on-1 with me.
What low Vitamin B12 can mean
- Vegan or vegetarian diets
- Older age and low stomach acid
- Acid-blocking medications and metformin
- Pernicious anemia and gut conditions such as celiac disease
- Weight-loss surgery
What high Vitamin B12 can mean
- Supplements or injections
- Some liver or blood conditions (follow up with your provider)
What affects Vitamin B12
- Diet
- Stomach acid and intrinsic factor
- Medications
- Gut health
Ways to support healthy levels
- Eat B12-rich foods such as meat, fish, eggs and dairy
- Use supplements if you are plant-based or have absorption issues
- Injections may be needed for pernicious anemia
- Check MMA and homocysteine if results are borderline (see who should consider vitamin B12)
Vitamin B12 and healthy aging
B12 supports DNA synthesis, methylation and mitochondrial energy production. Deficiency can contribute to genomic instability, epigenetic changes and nerve damage, which is why B12 status matters more with age.
Related tests and articles: folate, ferritin.
When to see a naturopathic doctor
- Fatigue, numbness, tingling or memory changes
- You are plant-based or over 60
- You take metformin or acid blockers
- Anemia or high homocysteine
See a medical provider promptly for numbness, weakness, balance problems or confusion. B12 deficiency can cause lasting nerve damage if untreated.
Want help making sense of your labs?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Frequently asked questions
What are symptoms of low B12?
Fatigue, numbness or tingling, memory problems, mood changes and anemia.
Can metformin lower B12?
Yes. Long-term metformin use is linked with lower B12.
What is MMA?
Methylmalonic acid is a test that rises when B12 is low at the tissue level.
Do vegans need B12 supplements?
Sources
- Green R. Vitamin B12 deficiency from the perspective of a practicing hematologist. Blood 2017. PMID: 28360040. https://pubmed.ncbi.nlm.nih.gov/28360040/
- Atkinson M, Gharti P, Min T. Metformin use and vitamin B12 deficiency in people with type 2 diabetes. What are the risk factors? A mini-systematic review. touchREV Endocrinol 2024. PMID: 39526048. https://pmc.ncbi.nlm.nih.gov/articles/PMC11548349/
- Bailey RL, et al. Modeling a methylmalonic acid-derived change point for serum vitamin B-12 for adults in NHANES. Am J Clin Nutr 2013. PMID: 23803883. https://pmc.ncbi.nlm.nih.gov/articles/PMC3712554/
- Pawlak R, Lester SE, Babatunde T. The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature. Eur J Clin Nutr 2019. PMID: 27381013. https://pubmed.ncbi.nlm.nih.gov/27381013/
- MedlinePlus: Vitamin B12 Level
- NIH Office of Dietary Supplements: Vitamin B12 (Consumer Fact Sheet)
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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