Are vitamin B12 injections more effective than vitamin B12 tablets for treating diabetic nerve damage?

This study compared mecobalamin (vitamin B12) injections with mecobalamin tablets for the treatment of diabetic peripheral neuropathy (DPN; nerve damage). It showed that after 8 weeks of treatment, patients treated with mecobalamin injections showed signs of nerves being repaired, while no effects were seen in those taking the tablets.  

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes. It results from damage to the nerves of the hands and feet, causing pain and loss of function. It can also affect nerves elsewhere causing problems such as urinary incontinence (leakage) and erectile dysfunction.

Nerve conduction studies are the normal method of assessing nerve function. However, this test can only look at larger nerves. It cannot see the subtle changes in small nerves that indicate nerve repair. The eye is the only place in the body where nerves can be seen. Looking at the small nerves in the eye with a very strong microscope, it is possible to identify early signs of nerve repair.

Mecobalamin is a form of vitamin B12, which is known to support nerve healing and repair. Mecobalamin can be given in injection or tablet form. It is not clear which form of mecobalamin is more effective in patients with DPN.

32 patients with DPN participated in this study. 15 received mecobalamin injections into the muscles (0.5 mg/day, 3 times/week), while 17 received mecobalamin tablets  (1.5 mg/day). Specialized eye exams were performed at the start and after 8 weeks of treatment to monitor signs of nerve repair.

Injection treatment resulted in significant improvements in all signs of nerve repair. These signs included the length and density of the nerve fibers in the eye. Tablet treatment did not result in an improvement in these signs.

This study showed that mecobalamin injections are more effective than mecobalamin tablets in aiding nerve healing and repair in DPN.

This study only followed patients for 8 weeks. They intended to follow patients for 24 weeks but due to the COVID-19 pandemic, this was not possible. Also, the number of participants was very small. More studies are needed to see if mecobalamin injections are more effective than tablets over a longer period of time.