From the Guidelines
Vitamin B12 shots generally do not directly affect blood glucose levels in most people, and you can safely receive B12 shots without worrying about significant glucose fluctuations. The primary function of vitamin B12 is in red blood cell formation, neurological function, and DNA synthesis, rather than directly influencing carbohydrate metabolism 1. However, it's essential to note that metformin, a common medication for type 2 diabetes, may be associated with biochemical vitamin B12 deficiency, and periodic measurement of vitamin B12 levels should be considered in metformin-treated patients, especially in those with anemia or peripheral neuropathy 1.
- B12 injections typically contain cyanocobalamin or hydroxocobalamin and are administered intramuscularly at doses ranging from 1,000-5,000 mcg depending on the condition being treated.
- For those with diabetes or blood sugar concerns, it's still advisable to monitor your glucose levels after your first few injections to observe any individual response.
- Correcting a B12 deficiency may indirectly improve overall metabolic health, which could stabilize glucose regulation over time 1.
- If you experience any unusual changes in blood sugar after B12 injections, consult your healthcare provider for personalized guidance. The most recent and highest quality study on pharmacologic approaches to glycemic treatment, published in 2022, does not provide direct evidence on the effect of vitamin B12 shots on blood glucose levels, but it emphasizes the importance of a patient-centered approach to choosing appropriate pharmacologic treatment of blood glucose, considering factors such as efficacy, hypoglycemia risk, and patient preferences 1.
From the Research
Vitamin B12 Deficiency and Metformin Therapy
- Metformin therapy has been associated with an increased prevalence of vitamin B12 deficiency in patients with type 2 diabetes 2, 3, 4.
- The exact mechanism of metformin-induced vitamin B12 deficiency is not fully understood, but it is thought to be related to impaired vitamin B12 absorption 2.
- Vitamin B12 deficiency can lead to a number of clinical consequences, including hematologic abnormalities, progressive axonal demyelination, and peripheral neuropathy 2, 5.
Prevalence of Vitamin B12 Deficiency
- The prevalence of vitamin B12 deficiency in patients with type 2 diabetes on metformin therapy has been reported to be as high as 36.54% 4.
- The risk of vitamin B12 deficiency may be higher in females, those with a longer duration of type 2 diabetes, and those taking higher doses of metformin 4.
- However, not all studies have found a significant association between metformin use and vitamin B12 deficiency 6.
Screening and Treatment
- Screening for vitamin B12 deficiency may be warranted in patients with one or more risk factors, such as gastric or small intestine resections, inflammatory bowel disease, or use of metformin for more than four months 5.
- Oral administration of high-dose vitamin B12 (1 to 2 mg daily) is as effective as intramuscular administration for correcting anemia and neurologic symptoms 5.
- Patients who have had bariatric surgery should receive 1 mg of oral vitamin B12 per day indefinitely 5.