Nearly 30% of adults with type 2 diabetes taking metformin in Georgia had low vitamin B12 levels, according to Gram Research analysis of 972 patients. Rates varied sharply by region, reaching 51% in western rural areas compared with 4.38% in eastern rural areas and 9.0% in urban areas.
Many people with type 2 diabetes take metformin, a common medicine that lowers blood sugar. Metformin is known to affect vitamin B12 absorption, so researchers wanted to see how common low B12 is in this group. According to Gram Research analysis of a 2026 study, about 30% of 972 adults in Georgia who had taken metformin for at least a year had low vitamin B12 levels. The rates differed sharply by place. In western rural areas, about half of the patients were low in B12, while eastern rural and urban areas had much lower rates. The study could not confirm why these differences exist, and diet is one possible factor that was not directly measured. The findings suggest that people taking metformin long term may benefit from having their B12 levels checked, especially in regions where deficiency appears more common.
Key Statistics
A 2026 cross-sectional study of 972 adults with type 2 diabetes in Georgia found that 29.53% had low vitamin B12 levels while taking metformin.
The same 2026 study found that 51% of patients in Georgia’s western rural region had vitamin B12 deficiency, compared with 4.38% in eastern rural areas and 9.0% in urban areas.
In a 2026 study of 972 adults taking metformin, the average serum vitamin B12 level was 354.65 pg/mL, with a standard deviation of 141.93 pg/mL.
The Quick Take
- What they studied: Researchers wanted to know how many adults with type 2 diabetes who take metformin have low vitamin B12, and whether this differs by region, age, sex, or how much medicine they take.
- Who participated: The study included 972 adults with type 2 diabetes in Georgia who had taken metformin at a daily dose of 1000 to 2000 mg for at least 12 months. Participants came from eastern rural, western rural, and urban areas.
- Key finding: About 29.5% of participants had low vitamin B12 levels. The average B12 level was 354.65 pg/mL, and the western rural region had the highest rate of low levels at 51%, compared with 4.38% in eastern rural areas and 9.0% in urban areas.
- What it means for you: If you take metformin long term, it may be worth asking your doctor whether your vitamin B12 level should be checked. This study cannot prove that metformin causes low B12, so do not stop or change your medicine without talking to your healthcare provider.
The Research Details
This was a retrospective cross-sectional study. That means researchers looked back at existing patient records and took a snapshot of B12 levels at one point in time, rather than following people over several years. Their goal was to measure how common low B12 was and to see whether it was linked to factors such as medicine dose, how long someone had taken metformin, sex, or age.
The team gathered data from 972 adults with type 2 diabetes who were taking metformin. They grouped patients by region, including eastern rural, western rural, and urban areas, so they could compare B12 levels across different parts of Georgia. Blood test results were used to measure each person’s B12 level.
Because the study looked at records from a single point in time, it can show that two things are connected, but it cannot show that one causes the other. Researchers also used statistical tests to check whether differences between groups were likely due to chance.
A cross-sectional design is useful for finding out how common a problem is in a large group of people. With nearly 1,000 participants, the study gives a useful picture of B12 levels among people taking metformin in this part of the world. It also points to regional differences that future research can explore more closely.
However, this design cannot tell us whether metformin itself lowers B12 over time. To answer that question, researchers would need studies that follow the same people across several years and track their B12 levels as they start and continue treatment.
The study uses a fairly large sample of 972 adults, which makes its estimates more reliable than those from very small studies. It was published in BMC Research Notes, a peer-reviewed journal, which means outside experts reviewed it before publication.
Some details in the published abstract are unclear, including the exact cutoff used to define deficiency, so readers should interpret the numbers with some caution. The study also relied on past medical records, which can contain gaps or inconsistencies. Because it is a single snapshot, it cannot prove cause and effect.
What the Results Show
Overall, about 29.5% of the adults studied had low vitamin B12 levels. The average B12 level across all participants was 354.65 pg/mL, with a fairly wide spread of values. This means that many people in the group had levels in a healthy range, while a meaningful portion did not.
The biggest difference was by region. In western rural areas, about 51% of participants had low B12. In eastern rural areas, the rate was 4.38%, and in urban areas it was 9.0%. These gaps are large, which suggests that where people live may matter for B12 levels. The authors suggest that differences in diet across regions may play a part, but they did not measure diet directly, so this remains a possible explanation rather than a confirmed one.
The researchers also looked at how metformin dose and length of use related to B12 levels. They found only a very weak connection. The statistical measures for this link were very small, meaning that dose and duration explained only a tiny part of the differences in B12 among patients.
Researchers did not find meaningful differences in B12 levels across age groups, so older and younger adults in the study had similar averages. In urban areas, men had higher B12 levels than women, which suggests that sex may play some role in certain settings. These patterns are interesting, but they should be confirmed by other studies before drawing firm conclusions.
These secondary results are useful because they show which factors did not seem to matter much, such as age, and which factors may need more attention, such as sex and region. They help guide future research toward the questions that matter most.
Earlier research has consistently found that long-term metformin use is linked to lower vitamin B12 levels in some people. This study supports that general concern, since nearly 30% of participants had low levels. However, the weak link between dose or duration and B12 in this study suggests that metformin is probably not the only factor. Diet, absorption problems, and other health conditions may also contribute.
The large regional differences in this study are notable and are not always discussed in the broader research. They suggest that local factors could matter as much as the medicine itself, which highlights the need for studies in more diverse populations.
The study looked at past records at a single point in time, so it cannot show whether metformin causes low B12 or whether B12 levels change over time. Important details, such as diet, supplement use, and other medicines, were not directly measured, which limits how well researchers can explain the regional differences. The published summary also contains some unclear details about how deficiency was defined, which makes precise comparisons with other studies harder. Finally, the group came from one country, so the results may not apply to all populations in the same way.
The Bottom Line
Research suggests that people taking metformin long term should consider having their vitamin B12 level checked, since nearly 30% of patients in this study had low levels. Confidence in this recommendation is moderate, because the study is large but cannot prove cause and effect. People who notice symptoms such as tingling, numbness, unusual tiredness, or memory changes should mention them to their doctor promptly. Anyone considering B12 supplements should first discuss the right dose and whether they need one with a healthcare provider.
This research is most relevant to adults with type 2 diabetes who take metformin for a year or longer, especially those living in rural areas of Georgia or similar regions. Doctors, pharmacists, and diabetes care teams may also find these results useful when planning routine checkups. People who do not take metformin or do not have diabetes will not be directly affected by these findings, although general B12 health still matters for everyone.
If your B12 level is low, supplements or dietary changes may improve it over several weeks to a few months, though the exact timing depends on how low your level is and what is causing it. Symptoms such as tingling or fatigue may take longer to improve, sometimes several months. Regular blood tests, often every year or as your doctor advises, can show whether your levels are staying in a healthy range.
Frequently Asked Questions
Does metformin cause vitamin B12 deficiency?
Long-term metformin use has been linked to lower vitamin B12 in some people. A 2026 study of 972 adults in Georgia found only a very weak link between metformin dose or length of use and B12 levels, suggesting other factors such as diet may also play a role.
How common is vitamin B12 deficiency in people with type 2 diabetes?
In a 2026 study of 972 adults with type 2 diabetes taking metformin in Georgia, 29.53% had vitamin B12 deficiency. Rates differed widely by region, ranging from 4.38% in eastern rural areas to 51% in western rural areas.
Should people on metformin get their vitamin B12 checked?
Doctors often suggest periodic vitamin B12 testing for people on long-term metformin, especially if they notice tingling, numbness, or unusual fatigue. A simple blood test can confirm your level. Talk with your healthcare provider before starting any supplement.
What are the signs of low vitamin B12 in people taking metformin?
Common signs of low vitamin B12 include tingling or numbness in the hands or feet, unusual tiredness, weakness, and memory or mood changes. These symptoms can have other causes, so a blood test and a conversation with your doctor are the best way to find out.
Want to Apply This Research?
- Log whether you have had a vitamin B12 blood test, the date, and the result, along with your current metformin dose and how long you have taken it. Add a yearly reminder to ask your doctor about B12 testing, and record any symptoms like tingling, numbness, or unusual fatigue on a 1 to 5 scale each week.
- Use the app to log B12-rich foods such as eggs, fish, meat, fortified cereals, and dairy, and set a weekly goal of including at least three of these foods. If your doctor recommends a supplement, use the app’s reminder feature to take it at the same time each day.
- Track B12 test results, metformin dose, and symptoms over time to spot trends. Share the summary with your healthcare provider at each visit so they can decide whether testing needs to happen more often or whether a change in treatment makes sense.
This article summarizes a retrospective cross-sectional study and is for general education only. It cannot show that metformin causes vitamin B12 deficiency, and it is not medical advice. Do not start, stop, or change any medicine or supplement without talking to your doctor or pharmacist. If you have symptoms such as numbness, tingling, or severe fatigue, contact a healthcare provider promptly.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.