For most people considering taking vitamin B12 injections, side effects are generally not serious. However, in certain instances serious side effects may occur.
Physicians give Vitamin B12 injections, also known as cobalamin or cyanocobalamin injections, to patients that are suffering from anemia, fatigue or other symptoms of vitamin B12 deficiency. Patients that have pernicious anemia require lifelong vitamin B12 injections and may want to consider dietary changes for B12 deficiency. These injections are sometimes very painful as they are given deep under the skin, known as a deep subcutaneous injection, or into a muscle, called an intramuscular injection.
Common Side Effects of Injections of Vitamin B12
There are many side effects that patients may experience from injections of vitamin B12. 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 feeling, or a sense, of being swollen over the entire body
- Headache
- Joint pain
If any of these side effects become severe or troublesome, let your doctor know immediately.
Vitamin B12 Injections: Side Effects That are Uncommon and Serious
Vitamin B12 injections can result in serious side effects. Although this is a relatively rare occurrence, anyone taking vitamin B12 injections should be aware of the possibility. Call your doctor immediately if you experience any of the following side effects.
- A rapid heartbeat
- Chest pain
- Heart palpitations
- A feeling of tightness in the chest
- Rapid weight gain
- Muscle weakness
- Muscle pain
- Muscle cramps
- A feeling of extreme thirst
- Frequent urination
- Leg pain
- A sense of confusion
- Numbness
- Dizziness
- A tingling sensation
- Difficulty breathing
- Difficulty swallowing
- Shortness of breath with mild exertion or when lying down
- Unusual coughing
- Unusual wheezing
- A feeling of extreme tiredness or fatigue
- Swelling of the extremities including hands, arms, lower legs, feet or ankles
- Redness, pain or a feeling of warmth in one leg
- Tenderness or swelling in one leg
- A red skin color on the face
- A red skin color anywhere on the body
- Hives
- Itching
- Skin rash
Other vitamin B12 injections side effects may also occur. If you experience anything unusual while taking B12 injections let your doctor know as soon as possible.