From the FDA Drug Label
Cyanocobalamin is quantitatively and rapidly absorbed from intramuscular and subcutaneous sites of injection; The best area for B12 injections is either intramuscular or subcutaneous sites, as both are effective for absorption of cyanocobalamin 1.
- Intramuscular injection results in a peak plasma level within 1 hour.
- Subcutaneous injection is also effective, although the peak plasma level time is not specified. No specific area is recommended over another, as long as it is either intramuscular or subcutaneous.
From the Research
The most effective method for administering vitamin B12 is through sublingual tablets, which have been shown to be superior to intramuscular injections in restoring B12 levels 2. When considering the administration of vitamin B12, it's essential to prioritize methods that maximize absorption and minimize discomfort.
- The sublingual route has been demonstrated to increase the odds ratio for an increase in serum vitamin B12 levels compared to intramuscular injections, with a mean difference of 252 ± 223 ng/L vs. 218 ± 184 ng/L, p < 0.001 2.
- This approach overcomes the challenges associated with intramuscular injections, such as pain, nerve damage, and bleeding, making it a more patient-friendly option.
- Additionally, sublingual administration eliminates the need for rotating injection sites, reducing the risk of tissue damage and maintaining effective absorption of the medication.
- While intramuscular injections can be effective, the evidence suggests that sublingual tablets are a better choice for patients with vitamin B12 deficiency, with significant improvements in serum B12 levels and no reported adverse effects 2.
- It's also worth noting that oral vitamin B12 supplementation has been shown to improve muscle function among the elderly, highlighting the importance of adequate vitamin B12 status for overall health 3.