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Are There Any Side Effects of Taking a B12 1000 Supplement Daily?

author image Rae Uddin
Rae Uddin has worked as a freelance writer and editor since 2004. She specializes in scientific journalism and medical and technical writing. Her work has appeared in various online publications. Uddin earned her Master of Science in integrated biomedical sciences with an emphasis in molecular and cellular biochemistry from the University of Kentucky College of Medicine.

Vitamin B12 is an essential, water-soluble vitamin your body uses to generate proteins and keep your blood healthy. Adults should consume between 2.4 and 2.9 micrograms of vitamin B12 on a daily basis by eating foods that are rich in this nutrient, such as beef liver, rainbow trout or clams, the Office of Dietary Supplements reports. If you have vitamin B12 deficiency anemia due to low blood levels of this vitamin, your doctor may recommend daily treatment with 1,000 mcg of a vitamin B-12 supplement. The side effects of taking this daily supplement are limited, but should be discussed with your doctor before beginning treatment.


You may experience diarrhea as a side effect following treatment with a daily 1,000-mcg dose of vitamin B12. Diarrhea is a condition characterized by frequent bowel movement urges that produce loose or watery stools. If you develop diarrhea, you may also experience excess gas or abdominal pain or cramping. Persistent diarrhea may increase the amount of fluid your body loses each day and may cause dehydration. Consult your physician if diarrhea side effects persist or become severe while you are taking vitamin B12 supplements.

Skin Reaction

A skin reaction may occur after you take a dose of vitamin B12. You may notice the appearance of red, irritated patches of skin across your body. Your skin may also become unusually dry or itchy, warns. If possible, avoid scratching irritated skin, as doing so may increase your risk of developing a skin infection.

Low Vitamin B12 Side Effects

Daily 1,000-mcg doses of vitamin B12 may be recommended by your doctor if you have low blood levels of the vitamin. Symptoms of vitamin B12 deficiency anemia, also called pernicious anemia, include bowel movement changes, diminished appetite, breathing difficulties, poor concentration, numbness or tingling, fatigue, pale skin, oral swelling or bleeding gums. Talk with your doctor if you exhibit any of these symptoms to ensure you receive appropriate treatment and care.

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