Can taking Metformin lead to Neuropathy?

It is estimated that 424.9 million people live with diabetes, and this number is expected to grow to 628.6 million by 2045. Diabetes is also one of the leading cause of death. According to the report from the World Health Organization (WHO), 43% of deaths before the age of 70 are caused by hyperglycemia aka elevated blood sugar a key factor in Type 2 Diabetes (T2DM) in addition to insulin resistance. One of the most common treatments for T2DM management is the drug Metformin. Metformin works to help regulate blood sugar levels and lower HbA1c levels. But can Metformin lead to neuropathy?

What is neuropathy?

Most people are familiar with the sequela of unchecked diabetes management which is poor wound healing in the feet or legs and diabetic neuropathy. This is a huge concern for those with neuropathy as if unchecked could lead to foot or leg amputation. Diabetic neuropathy is a type of nerve damage that occurs from prolonged high blood sugar levels. This leads the nerves and small blood vessels in the feet to be compromised where people get numbness aka ‘can’t feel their feet’ and often don’t realize there may be sores or wounds on their feet that don’t heal. You can develop neuropathy, nerve damage, even if you do not have diabetes. Other causes for neuropathy are trauma to nerves during surgery, vitamin B12 deficiency, nervous system diseases like Multiple Sclerosis, chemo-induced neuropathy, or idiopathic aka ‘no known cause.’ However, there are some studies that has investigated whether Metformin can actual lead to neuropathy. 

How can Metformin lead to neuropathy?

It has been found that Metformin can decrease vitamin B12, especially in those who are on metformin for a long-time. Most people when placed on Metformin are taking it for decades, most for the rest of their life. And recent studies show, chronic metformin use results in vitamin B12 deficiency in 30% of patients. Vitamin B12 deficiency, which may present as a peripheral neuropathy, is often misdiagnosed as diabetic neuropathy. Vitamin B12 deficiency may cause demyelination of nerves and has been associated with peripheral neuropathy, which is the loss of sensation in peripheral nerves, and weakness in lower extremities. 

A recent study in the Journal of Diabetes, showed patients taking metformin had a significantly higher risk of vitamin B12 deficiency and Metformin use was also associated with significantly greater percentage decrease in serum vitamin B12 concentrations from baseline in diabetic patient.

Failure to diagnose the cause of the neuropathy will result in progression of central and/or peripheral neuronal damage which can be arrested but not reversed with vitamin B12 replacement. 

In the Journal of Diabetes, Obesity, and Metabolism from 2022 proposed this possible mechanism. Metformin blocks the absorption of vitamin B12 through a mechanism that has not been established but could be because of interference with the calcium-dependent binding of the intrinsic factor vitamin B12 complex to a receptor in the terminal ileum. The subsequent deficiency of vitamin B12 may cause or accelerate distal symmetrical and autonomic neuropathy in the patient with diabetes. 

Why is this so important?

At Starting Point, we have many patients come in our office with diabetes, neuropathy, or both. Many are on minimum 10 medications, including metformin. In addition, most people know “if they don’t manage their diabetes they may loose their feet” but many do not know why. Also, many people know the association with it and diabetes but that their doctor “has nothing they can do to help” and think the Metformin will help prevent neuropathy, which in some cases in can make it worse.

This is why we specialize in helping those with chronic cases and 90% of our practice are those with neuropathy. There is hope for finding relief and as one of our patients put it “saving his foot.”

If you suffer from neuropathy and not finding relief from standard therapies. Give our office a call today at (425) 686-4498 to set-up your consultation to learn how we can help.

Dr. Ellie Heintze, ND, LAc, is a naturopathic doctor and acupuncturist in Bothell, WA at her practice Starting Point Acupuncture. She specializes in chronic and complex cases and commonly treats neuropathy, fibromyalgia, migraines, autoimmune, and infertility cases. Dr. Ellie Heintze is also the author of the book, A Starting Point Guide to Going Gluten-Free  and Keep Calm and Zen Out available on Amazon.

Sources:

https://www.sciencedirect.com/science/article/abs/pii/S1744388119300052

https://europepmc.org/article/med/20134380

https://onlinelibrary.wiley.com/doi/abs/10.1111/1753-0407.12900

https://onlinelibrary.wiley.com/doi/abs/10.1111/1753-0407.12900

https://dom-pubs.onlinelibrary.wiley.com/doi/abs/10.1111/dom.14734

Neuropathic Pain: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431761/#:~:text=Neuropathic%20pain%20in%20the%20general,between%203%25%20and%2017%25.

Role of vitamin B12 and neuropathy: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3376015/#:~:text=B12%20deficiency%20may%20cause%20demyelination,adults1%2C%2014%E2%80%9316.