From the Research
Vitamin B12 injections are not specifically indicated for fibromyalgia, and should only be used in patients with a documented B12 deficiency, as determined by blood tests measuring serum B12 levels, methylmalonic acid, and homocysteine 1. The most recent and highest quality study, a systematic review and meta-analysis published in 2025, found no significant difference in vitamin B12 levels between fibromyalgia patients and healthy controls 1. This suggests that vitamin B12 supplementation is unlikely to provide additional benefit for patients with fibromyalgia who have normal B12 levels. In cases of confirmed deficiency, typical replacement involves intramuscular injections of 1000 mcg cyanocobalamin or hydroxocobalamin, with the frequency and duration of treatment individualized based on the cause of the deficiency and the patient's response to treatment 2. Some key points to consider when treating fibromyalgia patients with vitamin B12 injections include:
- The importance of documenting a B12 deficiency before initiating treatment
- The need for individualized treatment regimens, as responses to treatment may vary considerably
- The potential for false expectations and lack of additional benefit in patients with normal B12 levels
- The importance of focusing on evidence-based treatments for fibromyalgia, including physical activity, cognitive behavioral therapy, and medications specifically approved for fibromyalgia, such as pregabalin, duloxetine, or milnacipran 3. Overall, while some patients with fibromyalgia may report subjective improvement with B12 supplementation, the current evidence does not support the use of vitamin B12 injections as a standard treatment for this condition, except in cases of documented deficiency.