Can You Take Too Much Vitamin B12 And What Are The Side Effects? (2024)

Vitamin B12 is essential for nerve health, DNA creation, and red blood cell formation. While it’s water-soluble and excess amounts are excreted, mega dosing may cause side effects like acne and rosacea. High doses might increase the risk of bone fractures. Most people can meet the recommended daily intake through diet, and supplementation should be discussed with a doctor.

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• B12
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Vitamin B12 (also known as cobalamin) is a water-soluble nutrient that forms red blood cells, produces DNA and energy, and helps to regulate cell metabolism and the functioning of your body’s nerves.

Foods like dairy products, fish, meat, and poultry are naturally high in vitamin B12, and some foods have vitamin B12 added to them, like breakfast cereal. Vitamin B12 oral supplements are also available. Vitamin B12 intravenous (IV) infusions, injections, and nasal sprays are other options, but these are usually used to treat vitamin B12 deficiency, not used as a way to maintain normal levels of vitamin B12.

This article will discuss whether it’s possible to overdose on vitamin B12, the levels at which someone might overdose, and what can happen if so.

Is it Possible to Overdose on Vitamin B12?

Vitamin B12 is a water-soluble vitamin, so it’s generally considered safe even at high doses. There is currently no Tolerable Upper Intake Level (UL) for B12 because there isn’t enough scientific evidence to establish one. Any excess B12 that your body doesn’t use gets flushed out in your urine.

However, if you supplement with excessive amounts of vitamin B12 (also called megadosing), you may experience some negative side effects. Some studies suggest that megadoses, especially from vitamin B12 injections, can cause acne and rosacea, which is a skin condition that forms red patches on your face.

The recommended daily intake (RDI) of vitamin B12 is 2.4 micrograms (mcg) for both men and women. Pregnant women need 2.6 mcg per day, and breastfeeding women should take 2.8 mcg every day. For those with a vitamin B12 deficiency, a dose of 1,000 mcg via the intramuscular route is recommended once a month. Newly diagnosed patients should receive 1,000 mcg intramuscularly once a week for four weeks to replenish stores before switching to once-monthly dosing.

While doses up to 2,000 mcg can be used safely to treat vitamin B12 deficiency, you should not take such high doses if you do not have a deficiency and if your doctor hasn’t recommended it.

Regarding absorption, your body only absorbs about 10 mcg of a 500-mcg dose if you do not have a vitamin B12 deficiency. This is because the absorption of B12 is dependent on intrinsic factor, a protein made in your stomach. Conditions like pernicious anemia, atrophic gastritis, and certain gastrointestinal surgeries can affect the production of intrinsic factor, thereby impairing B12 absorption.

While high doses of vitamin B12 are generally safe for most people, it’s important to follow recommended guidelines and consult with your doctor before starting any new supplement regimen.

How Much Vitamin B12 Does it Take to Overdose?

As stated previously, vitamin B12 overdose is unlikely because it is water-soluble, and your body flushes out any excess through urine. There is no upper limit for B12 since there isn’t enough scientific evidence to establish one. While doses up to 2,000 mcg can be safely used to treat B12 deficiency, you should not take such high doses without a deficiency or your doctor’s recommendation.

Absorption of B12 depends on intrinsic factor, a stomach protein, and certain conditions can affect this process. Signs of too much B12 include acne and rosacea, indicating elevated B12 levels.

What Can Happen if I Have too Much Vitamin B12?

While vitamin B12 is generally safe, excessive amounts can lead to some side effects. High levels of vitamin B12 might cause frequent headaches and gastrointestinal problems like diarrhea, nausea, and vomiting. You may also feel tired, weak, or experience a tingling sensation in your hands and feet.

More serious side effects from vitamin B12 injections can include pulmonary embolism and congestive heart failure, especially early in treatment. There’s also a risk of vein thrombosis, which increases the likelihood of developing blood clots. In rare cases, vitamin B12 can cause a severe allergic reaction called anaphylaxis, which happens if you are allergic to cyanocobalamin or cobalt. Anaphylaxis is life-threatening and causes swelling of the face, tongue, and throat, making it difficult to breathe and swallow. Immediate medical attention is necessary if this occurs.

It’s important to note that while vitamin B12 supplements are generally considered safe at appropriate doses, interactions with certain medications can affect B12 absorption. These include aminosalicylic acid, colchicine, metformin, proton pump inhibitors, and vitamin C supplements. To avoid interactions with vitamin C, take it two or more hours after your vitamin B12 supplement.

Vitamin B12, combined with folic acid and vitamin B-6, was once thought to reduce heart disease risk by lowering hom*ocysteine levels. However, studies show this combination does not significantly impact cardiovascular disease or stroke risk. Although B12 deficiency is linked to dementia and low cognitive function, it’s unclear if supplements can prevent or treat these conditions. Also, there’s no evidence to prove that B12 boosts energy or athletic performance unless you have a deficiency.

Vitamin Toxicity occurs when a person takes an excessive amount of a vitamin or vitamins, typically through supplementation. Different vitamins have different thresholds, with varying degrees of symptom severity depending on the vitamin.

“Vitamin B12 toxicity” refers to an overload of this vitamin. However, there isn’t an established toxic level for B12, and most people are unlikely to experience an overdose. This is because the body metabolizes B12 efficiently. When you consume B12, your body absorbs what it needs through a protein called intrinsic factor in your stomach. Any excess B12 is quickly processed by your kidneys and flushed out through your urine. This rapid elimination process helps prevent the build-up of B12 in your system, making toxicity very unlikely.

With that said, in one case study, a young woman taking high doses of B12 injections for pernicious anemia developed acne, face redness, insomnia, headache, and palpitations. Her symptoms improved on their own within two weeks of stopping daily B12 usage. Additionally, a recent study found that high blood concentrations of B12 appeared to be linked with early death, though researchers are unclear why at this time.

The Recommended Daily Allowance (RDA) for Vitamin B12 is 2.5mcg, which most people can obtain through their diet. If you want to increase B12 levels without using supplements, you can obtain this vitamin through foods such as meat, poultry, eggs, fish, fortified cereals, and dairy products.

Last Words

Vitamin B12 is a water-soluble member of the B-complex family that is necessary for nerve health, DNA creation, red blood cell formation, metabolic health, and more. This vitamin cannot be made by your body and must be obtained from outside sources such as diet and supplements. Most people can obtain the recommended 2.9mcg of B12 through their daily diet.

Vitamin B12 supplements may offer many potential health benefits, including helping improve mood, supporting bone and eye health, promoting healthy DNA and red blood cell creation, and more. There is currently no established Tolerable Upper Intake Level for Vitamin B12 because it is water-soluble, not stored by the body, and excess amounts are naturally excreted as waste. As such, it is unlikely for most people to experience a B12 overdose from taking too much of this vitamin.

If you want to supplement with Vitamin B12, it’s important to speak with your doctor first. They can advise you if doing so is safe and can help you reach your health goals.

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• Vitamin Spotlight: Vitamin B12
• How to Improve Your Energy Levels with IV Therapy and B12 Shots