Researchers tested whether taking more vitamin B12 helps people with diabetes who have nerve damage and low B12 levels. They gave some patients 1000 micrograms daily and others 2000 micrograms daily for 16 weeks. Both groups felt better—their nerve pain decreased and their symptoms improved. Interestingly, taking the higher dose didn’t work better than the lower dose for reducing pain, though it did raise B12 levels higher in the blood. The lower dose had a bonus benefit: it helped improve blood sugar control. This suggests that for nerve pain relief, the lower dose of B12 might be just as good as the higher dose.

The Quick Take

  • What they studied: Whether taking 1000 or 2000 micrograms of vitamin B12 daily works better for reducing nerve pain and damage in people with diabetes who don’t have enough B12 in their blood.
  • Who participated: 32 adults with type 2 diabetes who had nerve damage in their feet and low vitamin B12 levels (below 200 pg/mL). They were split into two groups and followed for 16 weeks.
  • Key finding: Both doses reduced nerve pain significantly. The 1000 mcg group’s pain scores dropped from 7.0 to 5.6, and the 2000 mcg group’s dropped from 6.2 to 4.4 (on a scale where higher numbers mean more pain). The higher dose didn’t work noticeably better than the lower dose for pain relief.
  • What it means for you: If you have diabetes with nerve damage and low B12, taking 1000 mcg of B12 daily may be enough to help your symptoms—you might not need to take twice as much. However, talk to your doctor before starting any supplement, especially if you have kidney concerns, since the higher dose showed some kidney function changes.

The Research Details

This was a randomized controlled trial, which is one of the strongest types of research studies. Researchers randomly assigned 35 adults into two equal groups: one taking 1000 micrograms of B12 daily and the other taking 2000 micrograms daily. Both groups took their vitamin for 16 weeks (about 4 months). The researchers measured nerve pain and damage using three different tests to make sure they got accurate results. They also checked blood B12 levels and other health markers before and after the study.

The study used methylcobalamin, which is a specific form of B12 that the body can use easily. Researchers chose people who had type 2 diabetes, nerve damage in their feet (called diabetic peripheral neuropathy), and confirmed low B12 levels. This careful selection meant the results would apply specifically to people with this combination of conditions.

Using a randomized controlled trial design is important because it reduces bias—randomly assigning people to groups helps ensure the groups are similar at the start. Measuring outcomes with multiple tests (three different nerve damage assessments) makes the results more reliable. The 16-week timeframe is long enough to see real changes but short enough to complete the study with most participants finishing.

This study had a relatively small group (35 people), which means the results should be viewed as preliminary rather than definitive. However, 32 of 35 people completed the full study, which is good follow-through. The study was published in The Journal of Nutrition, a respected scientific journal. The researchers measured multiple outcomes and reported both positive and concerning findings (like the kidney function changes), which suggests honest reporting. The study was well-designed with clear inclusion criteria and standardized measurement tools.

What the Results Show

Both vitamin B12 doses significantly reduced nerve pain over 16 weeks. In the 1000 mcg group, pain scores on the Numeric Rating Scale dropped from 7.0 to 5.6 (a decrease of 1.4 points, p=0.016). In the 2000 mcg group, pain scores dropped from 6.2 to 4.4 (a decrease of 1.8 points, p=0.007). Both improvements were statistically significant, meaning they weren’t due to chance.

When doctors examined the nerves using the Michigan Neuropathy Screening test, both groups showed improvement. The 1000 mcg group improved from 5.7 to 5.2 (p=0.033), and the 2000 mcg group improved from 5.4 to 4.5 (p=0.022). Again, both groups improved similarly.

Blood B12 levels increased in both groups, but the 2000 mcg dose produced higher B12 levels in the blood (p=0.049). However, this higher blood level didn’t translate to better nerve pain relief.

A third nerve damage test (Neuropathy Disability Score) showed no significant change in either group, suggesting that while pain and symptoms improved, some measures of nerve function didn’t change much in 16 weeks.

An interesting finding was that the lower 1000 mcg dose was associated with improved blood sugar control (lower HbA1c levels), which is a marker of long-term diabetes management. This suggests B12 might help with blood sugar in addition to nerve pain. However, the higher 2000 mcg dose showed a concerning decline in kidney function (lower eGFR scores), which warrants caution and further investigation. This kidney finding is particularly important for people with diabetes, who are already at higher risk for kidney problems.

Previous research has shown that B12 deficiency can worsen nerve damage in people with diabetes. This study confirms that supplementing B12 helps reduce symptoms. However, most previous studies didn’t directly compare different doses, so this research adds new information about whether ‘more is better.’ The finding that both doses work similarly is somewhat surprising and suggests the body may have a threshold for B12 effectiveness in treating nerve pain.

The study was small (only 35 people), so results may not apply to everyone. The 16-week timeframe is relatively short—longer studies might show different results. The study didn’t include a placebo group (people taking fake pills), so we can’t be completely sure the improvements weren’t partly due to placebo effect, though the specific measurements used make this less likely. The concerning kidney function changes in the high-dose group need further study in larger populations. The study only included people with type 2 diabetes, so results may not apply to people with type 1 diabetes or other conditions.

The Bottom Line

If you have type 2 diabetes with nerve damage and confirmed low B12 levels, taking 1000 mcg of B12 daily appears to be effective for reducing nerve pain and may also help blood sugar control. There’s moderate confidence in this recommendation based on this study. The 2000 mcg dose didn’t provide additional pain relief benefits and showed potential kidney concerns, so the lower dose may be preferable. Always consult your doctor before starting B12 supplements, especially if you have kidney disease or take certain medications.

This research is most relevant for adults with type 2 diabetes who have nerve damage in their feet and confirmed low B12 levels (below 200 pg/mL). People with kidney disease should be especially cautious about the higher dose. This may be less relevant for people with type 1 diabetes or those with normal B12 levels. If you have nerve pain from diabetes but normal B12 levels, this study doesn’t necessarily apply to you.

Based on this study, you might expect to notice improvements in nerve pain within 16 weeks (4 months) of starting B12 supplementation. Some people may notice changes sooner, while others may take the full 4 months. Blood sugar improvements appeared in the lower-dose group, suggesting metabolic benefits may develop over similar timeframes. However, individual responses vary, so discuss realistic expectations with your healthcare provider.

Want to Apply This Research?

  • Track daily nerve pain using a 0-10 scale (where 0 is no pain and 10 is worst pain imaginable) at the same time each day. Record this weekly to monitor trends. Also track B12 supplement dose taken and any side effects. This creates a clear picture of whether supplementation is helping.
  • Set a daily reminder to take your B12 supplement at the same time each day (such as with breakfast) to build consistency. Log the dose taken in your app immediately after taking it. Additionally, track any changes in foot sensation, tingling, or numbness using simple descriptors (none, mild, moderate, severe) to notice patterns over time.
  • Create a weekly summary view showing pain scores, supplement adherence, and symptom descriptions. After 4 weeks, review trends to see if pain is decreasing. Share monthly reports with your healthcare provider to help them assess whether the current dose is working. If pain isn’t improving after 8 weeks, discuss with your doctor whether adjustments are needed. Continue monitoring kidney function and blood sugar markers as recommended by your doctor, especially if considering higher doses.

This research summary is for educational purposes only and should not replace professional medical advice. The study involved a small number of participants and lasted only 16 weeks, so results should be considered preliminary. The higher B12 dose showed concerning changes in kidney function in this study—if you have kidney disease or reduced kidney function, consult your doctor before taking high-dose B12 supplements. Always speak with your healthcare provider before starting any new supplement, especially if you have diabetes, kidney disease, or take medications that might interact with B12. This study applies specifically to people with type 2 diabetes, low B12 levels, and nerve damage; it may not apply to other conditions or populations. Individual results vary, and what works for one person may not work for another.