Oral vitamin B12 supplements are not generally associated with any side effects.
Although quite rare, serious allergic reactions to injections of vitamin B12 (sometimes even life-threatening) have been reported.29, 30 Whether these reactions are to the vitamin itself, or to preservatives or other substances in the injectable vitamin B12 solution, remains somewhat unclear. Most, but not all, injectable vitamin B12 contains preservatives.
In a double-blind trial, people with diabetes who also had with kidney disease received a daily placebo or 2.5 mg of folic acid, 1 mg of vitamin B12, and 25 mg of vitamin B6 for three years. Compared with the placebo, vitamin supplementation accelerated the decline in kidney function and increased the incidence of cardiovascular events (such as heart attacks) and heart disease-related deaths.31 Based on this study, diabetics with kidney disease should not take these vitamins without a doctor's supervision.
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The information presented by TraceGains is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2021.