The Hidden Side Effects Of Too Much Vitamin B12

Vitamin B12 is an important nutrient that plays a vital role in maintaining bodily systems. It's used for red blood cell development, cell metabolism, to keep nerves healthy, and to create DNA, according to the Mayo Clinic.

As with any nutrient though, too much can have drawbacks. Thankfully, the risk of that is very low with vitamin B12. That's because our bodies store what we need from this vitamin, then flush the excess through our urine. Most of us get the vitamin B12 we need through our diet, as it's found in meat, fish, and dairy. But many people also take a vitamin B12 supplement, which is generally considered safe.

Where an individual might run into problems is when they've been prescribed vitamin B12 injections by a doctor. These shots contain a much higher amount of the vitamin than over-the-counter supplements, and might come with side effects, according to Healthline. If you've been prescribed vitamin B12 injections and experience diarrhea, itching, rash, headaches, dizziness, nausea, or vomiting, speak with your doctor. Occasionally, very serious side effects can occur, including pulmonary edema or congestive heart failure, blood clots in veins, swelling, or a rare blood cancer called polycythemia.

How much vitamin B12 do you need?

There are a few people who should avoid supplementing with B12 at all, according to WebMD. Those who have a hereditary eye condition called Leber disease should skip B12 as, for them, it can damage the optic nerve. Anyone with an allergy or sensitivity to cobalt or cobalamin should also forgo B12 supplements. And if you've had a stent placed, don't take a combination of B12, folate, and B6. This mix could lead to an increased risk of narrowing of the blood vessels.

For most people, a recommended daily allowance of 2.4 micrograms per day is suggested, according to the National Institutes of Health. During pregnancy, that can be increased to 2.6 mcg and up to 2.8 mcg while breastfeeding. Do not take more than this amount, however, as it has not been tested for safety.

As with all supplements, if you notice any strange effects after starting vitamin B12 supplementation, then stop taking it and consult with your doctor. For the most part, though, this nutrient is safe and very important to a strong, healthy body.