Side Effects and Precautions of Vitamin B12

Are there any side effects of vitamin B12?

Vitamin B12 is considered to be non-toxic and has no side effects for generally healthy people and when used in appropriate dosages.

Although the "Upper Tolerable Intake Level" (Upper Tolerable Intake Level) of vitamin B12 has not been established, there is a risk of excessive B12 intake in large doses

Possible side effects or adverse reactions when taking large doses of vitamin B12 include: dizziness, headache, anxiety, nausea, vomiting, itching, acne (acne) and rosacea (rosacea)

In addition, there have been cases of severe allergic reactions caused by vitamin B12. Although it is extremely rare, it must still be noted. Symptoms include swelling of the face, tongue and throat, and difficulty swallowing and breathing. If these conditions occur after taking it, please seek medical help immediately.

Safety precautions (9 points of taboos)

1. A placebo-controlled study in older adults showed that daily folic acid (400 mcg) and vitamin B12 (500 mcg) supplementation for 2 to 3 years may increase the risk of colon cancer. Note 7

2. In patients with diabetic nephropathy, the use of high doses of B vitamins (containing 1000 mcg vitamin B12) may lead to decreased renal function and increased cardiovascular events. Note 8

3. Sublingual and dissolvable B12 supplements often contain sugar substitutes, which may cause bloating and diarrhea

4. An observational study pointed out that for pregnant women, if the vitamin B12 concentration in the blood is greater than 600 pmol/L, the incidence of autism in the child will be increased several times (the recommended daily intake of Vitamin B12 for pregnant women is 2.6 mcg ). Note 9

5. Taking folic acid, vitamin B6 and vitamin B12 after coronary artery stenting may increase the risk of in-stent restenosis. Note 10

6. Megaloblastic anemia is sometimes treated with vitamin B12, however due to possible side effects it is best used under close supervision by a medical professional

7. Do not take with antibiotics: Chloramphenicol may affect the ability of vitamin B12 to participate in the production of new red blood cells

8. The following drugs may inhibit the absorption of vitamin B12, such as antiepileptic drugs, chemotherapy drugs, gout drugs, bile acid binders, used to lower cholesterol, suppress gastric acid drugs, diabetes drugs, aminosalicylic acid, colchicine, metformin

9. Long-term use of high-dose folic acid (greater than 800 mcg) may cover up the phenomenon of Vitamin B12 deficiency, which can seriously cause damage to the nervous system. Therefore, long-term use of folic acid alone must be taken care of, or a comprehensive compound formula should be used to prevent it