What are the side effects and contraindications of vitamin B12?

Vitamin B12 may cause side effects such as allergic reactions, gastrointestinal discomfort, neurological abnormalities, cardiovascular symptoms, and injection site reactions. Contraindications include: individuals allergic to vitamin B12 should not use it; patients with gout, severe liver disease, or undiagnosed neurological disorders should use it cautiously; caution is also required when taken concurrently with certain medications. Vitamin B12 should be used properly and under medical guidance. If severe allergic reactions or persistent discomfort occur, prompt medical attention is recommended.

1. Side Effects of Vitamin B12

1. Allergic Reactions: Some individuals may experience skin itching, rashes, or erythema. In severe cases, urticaria, laryngeal edema, or even anaphylactic shock may occur. These reactions are often related to individual hypersensitivity. Use should be discontinued immediately if any such symptoms appear.

2. Gastrointestinal Discomfort: Common symptoms include nausea, vomiting, diarrhea, and bloating. Some people may also experience loss of appetite or oral malodor. These effects are usually due to irritation of the gastrointestinal mucosa by the medication or excessively high doses, and can often be relieved by adjusting the dosage.

3. Neurological Abnormalities: Occasional dizziness, headache, or drowsiness may occur. Rarely, mental excitement or restlessness may develop. These symptoms may be related to abnormal regulation of the nervous system by vitamin B12. Mild symptoms may be monitored without discontinuation.

4. Cardiovascular Symptoms: Palpitations or feelings of heart pounding may rarely occur. In severe cases, blood pressure fluctuations may be triggered, particularly in individuals with pre-existing cardiovascular conditions, who are at higher risk. Close monitoring of physical responses is advised.

5. Injection Site Reactions: When administered via injection, redness, pain, or nodules may occur at the injection site. These are often caused by improper injection technique or local tissue irritation from the drug. Following proper injection procedures can reduce these occurrences.

2. Contraindications for Vitamin B12

1. Hypersensitivity to Vitamin B12: Individuals allergic to vitamin B12 are at risk of severe allergic reactions that may endanger health. These individuals must absolutely avoid its use.

2. Use with Caution in Patients with Gout: Vitamin B12 may promote nucleic acid breakdown, increasing uric acid production, which could worsen gout symptoms or trigger acute attacks. Use should be cautious and under medical supervision.

3. Use with Caution in Patients with Severe Liver Disease: The liver plays a key role in vitamin B12 metabolism. In patients with impaired liver function due to severe liver disease, vitamin B12 use may increase hepatic burden. Dosage must be strictly controlled.

4. Use with Caution in Patients with Undiagnosed Neurological Disorders: Since vitamin B12 can improve certain neurological symptoms, using it without a clear diagnosis may mask the underlying condition and delay appropriate treatment.

5. Caution When Co-administered with Certain Medications: Concurrent use with drugs such as colchicine or metformin may impair vitamin B12 absorption. Combining with aminoglycoside antibiotics may reduce efficacy. Dosing should be staggered or adjusted according to medical advice.

Vitamin B12 supplementation should only be initiated after confirming deficiency, avoiding blind use. Oral formulations should be preferred under medical guidance. If injections are needed, they should be administered at qualified medical facilities. Regular follow-up tests are recommended to monitor relevant indicators and adjust the treatment plan based on individual health status.