Type 2 diabetes affects more and more people. The primary medication for the condition is metformin, which decreases blood sugar levels and improves insulin resistance. (1) Regrettably, metformin impedes  the utilization of vitamin B12 and prolonged use can lead to vitamin B12 deficiency. However, this problem is easily preventable through regular vitamin B12 supplementation. 

How common is vitamin B12 deficiency? 

Vitamin B12 deficiency affects a relatively large portion of the population. It’s more common in the elderly and people with diabetes. A study examining over 1000 people found it to be highly common among people with diabetes, and those who used metformin were much more likely to have vitamin B12 deficiency. (2) In several studies, the more metformin was used for the longer period, the lower vitamin B12 levels were measured. (3,4,5,6)  

Metformin and certain antacids block the absorption of vitamin B12 but only that which comes from food. (7) With large dose supplements, deficiency that would otherwise lead to serious neurological problems can be fixed. 

Vitamin B12 supplementation improves neuropathy in people with type 2 diabetes 

In a study published in 2021, researchers set out to explore whether methylcobalamin supplementation combined with the elimination of vitamin B12 deficiency improves the neuropathic symptoms of people with type 2 diabetes. (8) Neuropathy indicates several problems within the peripheral nervous system. It’s a very common symptom of type 2 diabetes, just like vitamin B12 deficiency, which, in turn, is one of the root causes of neuropathy.  

The study involved 90 participants. One group received a daily dose of 1000 mg methylcobalamin , while the other group received placebo. All participants had low vitamin B12 levels, 232 pmol/l on average, which is otherwise way above what’s typically regarded as deficiency. 

What were the results? 

As expected, vitamin B12 intake significantly increased the participants’ vitamin B12 levels. What’s even more important is that they had better results on seven different neuropathy tests. Their quality of life improved and their pain diminished, while the same cannot be said for the control group: they experienced no change and their pain only increased. This study serves as exceptional proof that vitamin B12 supplementation alone substantially improves neuropathy in diabetic people and effectively eliminates vitamin B12 deficiency. 

It improved blood sugar levels too 

A 2020 study examined vitamin B9 and B12 supplementation as complementary therapy for patients with type 2 diabetes who also received traditional medicinal treatment. (9) Researchers wanted to see whether vitamin 12 intake improves the blood sugar levels of participants and if their insulin sensitivity improves, as vitamins B9 and B12 have an important role in metabolism. 

Participants were divided into 4 groups: 

• Group A: 5mg folic acid per day in addition to traditional treatment 

• Group B: 500 mcg methylcobalamin per day in addition to traditional treatment 

• Group C: 5mg folic acid and 500 mcg methylcobalamin per day in addition to traditional treatment 

• Group D: Traditional treatment only 

HbA1c is a crucial blood sugar level indicator in people with type 2 diabetes: the higher the level, the more serious the condition. Vitamin B12 supplementation, as well as the combined intake of vitamins B9 and B12 significantly decreased the HbA1c levels of participants, and improved their insulin sensitivity as well compared to group D (traditional therapy). Vitamin B12 supplementation produced better results than folic acid. Combined intake proved to be the most effective in lowering HbA1c levels and improving insulin sensitivity. 

In summary, vitamin B12 intake is recommended to anybody who suspects deficiency, but it’s particularly important for people with type 2 diabetes who take metformin.