Can vitamin b12 injection cause reactions in the body?

B-12 injection side effects are very rare but it is good to know all the information pertaining to what you are putting in your body. The more common side effects include: mild diarrhea; upset stomach; nausea; a feeling of pain and a warm sensation at the site of the injection a sense of being swollen over the entire body; Headaches; and Joint pain.

Some of serious and rare side effects are chest pain, feeling of short breath, rapid weight gain. Call your doctor if you have been going through these symptoms.