Diabetes and prediabetes
Can a vegetarian diet or metformin lower your vitamin B12?
Both can. Vitamin B12 comes mainly from animal foods, so vegetarians, and especially vegans, can run low, and long-term metformin use is linked to lower B12 levels. If you have both, ask your doctor about a B12 blood test, particularly if you notice numbness, tingling or unusual tiredness.
Clinically reviewed by Dr. Ambily Kushal, RD, MS, PhD · Published · Last reviewed
Why does B12 matter?
B12 is needed to make red blood cells and to keep nerves working. Low levels can cause anemia and nerve damage.
Signs of low B12 include tiredness, weakness, pale skin, numbness or tingling in the hands and feet, balance problems, a sore tongue, and changes in memory or mood. They can come on slowly, and some are easy to mistake for other things.
Why are vegetarians at risk?
B12 is found naturally in animal foods. Lacto-ovo vegetarians get some from milk, yogurt, cheese and eggs; vegans need fortified foods or another source agreed with their doctor or dietitian.
- Dairy foods such as milk, yogurt and cheese.
- Eggs, for people who eat them.
- Fortified foods, such as some breakfast cereals, plant drinks and nutritional yeast; check the label.
How does metformin affect B12?
Long-term metformin use can reduce how much B12 the gut absorbs. In a large study, people taking it for years had a higher risk of low B12.
That is not a reason to avoid metformin, which is a well-established and widely used diabetes medicine. It is a reason for periodic B12 checks, especially if you also eat little or no animal food or have nerve symptoms.
Should I stop metformin if my B12 is low?
Don’t stop or change a prescribed medicine on your own. Any change to a medicine is a decision for the clinician who prescribed it.
If a test shows low B12, your doctor decides how to treat it and whether anything about your medicines should change. Your dietitian can help you raise B12-rich and fortified foods within a vegetarian diet. Any B12 supplement should be agreed with your doctor or dietitian.
What did this look like for one patient?
A vegetarian man with type 2 diabetes, on metformin, later reported intermittent numbness and tingling, and low B12 was raised as a possible cause to investigate.
His case shows a foreseeable risk of a long-term vegetarian diet, one that metformin can add to, and one that is easy to miss while attention is on blood sugar. It was being investigated rather than assumed, and one person’s course is not a promise of results.
What patients say about this kind of care
A vegetarian plan works best when it accounts for the nutrients that diet tends to miss.
“I am a vegetarian and she helped me a lot.”
A B12 result means more once someone explains it alongside your diet and medicines.
“She translated complex bloodwork and clearly explained what it revealed about my overall health in a way that's easy to understand”
Excerpts from patient reviews of Dr. Ambily Kushal, quoted word for word. Each describes one person’s care; individual experiences vary and are not a promise of results.
Frequently asked questions
How is B12 tested?
With a blood test, sometimes alongside folate or other markers. Your doctor decides which tests fit your situation.
How often should people on metformin be tested?
Guidance suggests periodic checks in long-term users, especially with nerve symptoms or anemia. Ask your doctor how often makes sense for you.
Can numbness from low B12 get better?
It often improves with treatment, especially when found early, but long-standing nerve damage may not fully recover. That is why early testing matters.
Can I get enough B12 from food as a vegetarian?
Many lacto-ovo vegetarians can, with dairy, eggs and fortified foods most days. Vegans, and anyone on long-term metformin, may need more, and a blood test tells you where you stand.
Does diabetes itself cause numbness?
Yes, diabetes can damage nerves too, which is one reason low B12 can be missed. Your doctor can look at both possibilities.
Sources
- Vitamin B12: Fact Sheet for Consumers (NIH Office of Dietary Supplements)
- Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study (Aroda et al., 2016) (Journal of Clinical Endocrinology and Metabolism)
- Metformin (MedlinePlus (National Library of Medicine))
- Vitamin B Test (MedlinePlus (National Library of Medicine))
Related reading
- Vegetarian diet and diabetes
- Lowering A1c on a vegetarian diet
- Dietitian and blood work
- Prediabetes and type 2 diabetes
- Nutrition answers
Our condition guides are general education, not medical advice. Talk with your doctor about your own diagnosis, tests and medicines.