Safety and side effects

When taken at appropriate doses, vitamin B-12 supplements are generally considered safe. While the recommended daily amount of vitamin B-12 for adults is 2.4 micrograms, higher doses have been found to be safe. Your body absorbs only as much as it needs, and any excess passes through your urine.

High doses of vitamin B-12, such as those used to treat a deficiency, might cause:

• Headache
• Nausea and vomiting
• Diarrhea
• Fatigue or weakness
• Tingling sensation in hands and feet