How Much Is Too Much When You’re Taking Vitamin B12?

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    If you can’t get all the vitamin B12 you need from your diet, supplementing is a good idea. How much to take? Is there such a thing as too much? Find out here.

    What is vitamin B12?

    Vitamin B12 is an important water-soluble vitamin that helps keep your nervous system and blood cells healthy. It also plays a key role in the body’s conversion of carbohydrates to glucose, in order to produce energy, and is essential in the making of RNA and DNA, the genetic foundation of our cells. It is also one of the 8 B vitamins that make up the B-Complex, and, as such, works in conjunction with other B’s to promote cognitive function, and support a healthy immune system.

    Vitamin B12 is not made in the body and must come from animal products such as meat, poultry, shellfish, dairy, eggs, and cheese. It can also be found in fortified foods such as bread, whole grains, cereals, orange juice, milk alternatives, and nutritional yeast. If you cannot meet your vitamin B12 needs with food, then you might consider supplementing.

    How is vitamin B12 absorbed in my body

    The absorption of Vitamin B12 is a two-step process that begins when the B12 is separated from the protein it is attached to by the hydrochloric acid and other enzymes in the stomach. Then, this free-form B12 combines with a protein made by the stomach called intrinsic factor, and the body absorbs the two together further down in the small intestines.

    Why I need vitamin B12

    Vitamin B12 is critical for your body’s optimal functioning and overall well-being. It supports cognitive health, the energy metabolism, and promotes a healthy nervous system. It also helps to maintain healthy levels of the amino acid homocysteine.

    In the HAIPEE study of men and women aged 45 to 69, high vitamin B12 levels were associated with better word recall and higher verbal fluency scores, though researchers called for more long-term studies before drawing conclusions about B12’s potential role in cognitive decline.

    Vitamin B12 deficiency

    Though vitamin B12 deficiency is not common, people who follow a vegan or vegetarian diet are more likely at risk because plant foods do not contain B12. Other populations who might be at risk for deficiency include pregnant or lactating people, the elderly, and those with digestive tract issues that may impact the absorption of nutrients. Medications like proton pump inhibitors may also limit a body’s capacity to absorb B12. Your vitamin B12 levels can easily be checked with a routine blood test by your physician.

    Health benefits of vitamin B12

    The body needs B12 for normal brain function, a healthy nervous system, protein synthesis, and the formation of healthy red blood cells. It also plays a role in mood, immune function, and healthy skin, hair, eyes and nails.

    The recommended dietary allowance (RDA) of vitamin B12 in healthy adults is 2.4 mcg. However, higher doses may be necessary for older people, those who are pregnant or lactating, people with digestive issues that impair absorption, or those who are taking certain medications.

    Potential side effects and adverse reactions

    Vitamin B12 supplements are generally considered safe. Because it is a water-soluble vitamin, any B12 that your body does not absorb will be excreted through your urine. Though the RDA of B12 for healthy adults is 2.4mcg, higher doses are used under certain circumstances, and with occasional minimal side effects. Most studies do not report side effects from B12 supplementation. Few sources report that digestive distress or a tingling sensation in the hands and feet may occur from higher doses, though it is uncommon. If you notice any of these symptoms be sure to talk to your doctor.

    Should I take a vitamin B12 supplement

    It is always best to get your vitamin B12 from a diet that includes meat, shellfish, seafood, poultry, Greek yogurt, dairy, cheese, and fortified foods, such as bread, milk, milk alternatives, and cereals. If you cannot get enough B12 from your diet, supplementation can help to bridge the nutritional gap. Since the natural sources of B12 are animal products, vegans and vegetarians should monitor their B12 levels and supplement accordingly. Older people, pregnant and lactating people, and those with absorption issues may benefit from supplementing with vitamin B12. Whenever considering new supplements be sure to check with your physician.

    Can you take too much vitamin B12?

    Being a water-soluble vitamin means that any vitamin B12 that your body does not absorb will be excreted through your urine. While there are guidelines and an RDA, no Tolerable Upper Intake Level (UL) has been determined for B12, given its low level of toxicity. Vitamin B12 is generally regarded as a safe vitamin to supplement with.

    How much of vitamin B12 is too much?

    The RDA of B12 is 2.4 mcg. If you are taking supplements, even one with no UL, it is always best to consult with your physician to determine suitable dosage and what the upper limit would be.

    Can you overdose on vitamin B12?

    There is no UL for vitamin B12 and any that your body doesn’t absorb is excreted through your urine. If you megadose, there is a slight increased potential that you may experience uncomfortable digestive side effects. If you are experiencing these symptoms from taking vitamin B12, you should consult your physician before continuing to take it.

    Are high doses of vitamin b12 harmful to your health?

    There is no data to indicate that a high dose of vitamin B12 is harmful to your health. Your body will not retain any that it does not absorb. If you do take too much for your own body, you may start to feel minor side effects like digestive distress and fatigue.

    Risks and side effects of taking too much vitamin b12?

    There is no UL for vitamin B12, but there is a recommended dose for healthy adults, which is 2.4mcg. Any amount that you take beyond that which your body uses will be excreted through your urine. If you begin to experience side effects like digestive distress, you should not take any more and talk to your healthcare provider about adjusting the dose to meet your needs.

    What to do if you take too much vitamin b12?

    If you are concerned that you have taken too much vitamin B12 and are experiencing serious symptoms, seek medical attention promptly.

    Final takeaways

    Vitamin B12 is essential for optimal health and well-being. Ideally, you will get all the B12 you need from a diet that includes meat, poultry, fish, seafood, dairy, eggs, and cheese. If you need more, supplementation can fill the nutritional gap. The recommended dosage for healthy adults is 2.4mcg and there is no UL. Larger doses may be needed depending upon your personal circumstances. Any you do not use, your body will excrete through your urine. As always, check with your physician before supplementing.

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    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
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