Last update: June 11, 2024

Vitamin B12: The Complete Guide

Explore the comprehensive guide on Vitamin B12, covering dosage recommendations, benefits, potential side effects, and more essential information for maintaining optimal health and wellness.

Stephanie Wright

By Stephanie Wright, RN, BSN

Edited by Dr. Dimitar Marinov, MD, MBA, PhD

Learn more about our editorial standards

Key takeaways

  • Vitamin B12 (Cobalamin) is crucial for neurological function and red blood cell formation.
  • B12 deficiency may cause fatigue, neurological issues, and anemia.
  • Dietary or supplemental intake is crucial, particularly for vegetarians and vegans.

    What is vitamin B12?

    Vitamin B12, also known as cobalamin, is an essential water-soluble vitamin that plays an important role in energy metabolism and plays a big role in overall well-being, supporting key physiological processes.

    Your body needs vitamin B12 for energy metabolism, red blood cell formation, and nerve health. Ensure a balanced diet or consider supplements to meet your vitamin B12 needs [1].

    Can your body produce vitamin B12?

    No, your body cannot naturally produce the full amount of vitamin B12 required. Only small amounts of the vitamin are produced by gut bacteria. You need to get the majority of your needs from dietary sources like meat, fish, dairy, or supplements. They support your overall health, so it’s important to ensure an adequate intake to maintain proper body functions [1].

    The energy vitamin

    Often referred to as the "energy vitamin," B12 plays a key role in converting carbohydrates into glucose, which fuels your body. It's why you often hear about B12 supplements for an energy boost.

    Diferent types of vitamin B12

    1. Methylcobalamin
      Methylcobalamin is a natural form of B12. It may be more suitable for certain people and is thought to be involved in unique biochemical processes beyond other B12 forms. It differs from cyanocobalamin in that the cyano group at the cobalt is replaced with a methyl group.
    2. Cyanocobalamin
      Cyanocobalamin is a synthetic form of vitamin B12. it's most prevalent supplement form due to its stability and cost-effectiveness. While it needs conversion to active forms in the body, it remains a widely used and accessible option.
    3. Hydroxocobalamin
      Hydroxocobalamin is also a synthetic form of vitamin B12. Known for its longer-lasting presence in the bloodstream, hydroxocobalamin offers potential therapeutic benefits for specific conditions. Its gradual release may be advantageous for people with specific health considerations.

    It's important to note that while these forms have some differences, they all serve as sources of vitamin B12. The choice of which form to use may depend on individual needs, preferences, and the advice of a healthcare professional.

    How does vitamin B12 work in your body?

    What are some benefits of vitamin B12?

    Vitamin B12 is essential for maintaining good health. Here are a few benefits of adding or maintaining sufficient vitamin B12 in your diet.

    1. Supports energy metabolism

      Supporting energy metabolism, vitamin B12 actively converts food into usable energy. This process is fundamental for sustaining vitality, promoting endurance, and supporting fatigue prevention [2].

    2. Boosts cognitive function and brain health

      B12 is important in supporting cognitive function and maintaining optimal brain health. It contributes to neurotransmitter synthesis, essential for efficient nerve signal transmission, and helps support the nervous system [3].

    3. Promotes red blood cell formation

      Integral to the formation of red blood cells, vitamin B12 ensures the efficient transport of oxygen throughout the body. This not only supports cardiovascular health but also may help support anemia and related issues [4].

    4. Supports immune system function

      B12 supports the immune system by playing a role in producing white blood cells. This immune response is essential for the body's defense against infections, contributing to overall health and well-being [6].

    What are some signs of vitamin B12 deficiency?

    Recognizing signs of vitamin B12 deficiency is crucial for maintaining overall health and well-being.

    • Fatigue and Weakness: Persistent fatigue and weakness may indicate a potential deficiency in vitamin B12, affecting energy levels and overall vitality [1].
    • Anemia: Vitamin B12 deficiency may lead to megaloblastic anemia, a condition characterized by the production of larger-than-normal red blood cells, impacting oxygen transport [1].
    • Neurological Issues: Neurological symptoms like tingling sensations, numbness, and difficulty walking may arise due to B12 deficiency, affecting the nervous system [1].
    • Cognitive Impairment: Deficiency in B12 may impact cognitive function, leading to memory loss, difficulty concentrating, and other cognitive impairments [1, 10].
    • Digestive Disturbances: Issues like diarrhea or constipation may occur, as vitamin B12 may play a role in maintaining a healthy digestive system.
    • Pale or Jaundiced Skin: Vitamin B12 deficiency may contribute to changes in skin color, with people appearing pale or developing a yellowish tint (jaundice) [1].

    Never self-diagnose

    If you feel you may have a deficiency or are concerned or curious about taking this supplement, talk to a doctor or healthcare professional. They can accurately diagnose and recommend the appropriate treatment plan for your specific needs.

    Sources of vitamin B12

    Vitamin B12 can be obtained from various sources, primarily from foods but also from supplements when dietary intake is insufficient.

    Vitamin B12-rich foods

    Below is a categorization of various foods based on their vitamin B12 content, helping you to identify sources that can boost your dietary vitamin B12 intake.

    Is food intake always the best?

    Obtaining vitamin B12 from food is generally recommended. However, in cases of significant deficiency, dietary restrictions, or certain health conditions, supplements may be necessary.

    Delivery methods

    Vitamin B12 supplements come in various delivery methods, each offering its own set of benefits and ways of consumption. Here's a brief overview of the different delivery methods:

    Choose a method that fits your routine

    Do not overlook the delivery method. Vitamin B12 supplements come in tablets, capsules, soft gel, chewable, powders, and liquid forms—choose the one that best fits your daily routine to stay consistent.

    What to look for in vitamin B12 supplements

    When selecting a supplement, several key factors must be considered to ensure you choose a high-quality product that effectively supports your health goals and overall well-being.

    • Dosage and potency

      The dosage of vitamin B12 in supplements varies, so it's important to choose one that aligns with your specific needs. This includes considering your age, gender, and health status, like pregnancy or existing deficiencies. The vitamin B12 formulation can impact its potency and bioavailability, which affects how effectively your body can absorb and use it.

    • Quantity and delivery method

      The delivery method is crucial. Vitamin B12 supplements come in various forms, including tablets, capsules, powders, chewables, and liquid forms. Your choice may depend on factors like ease of swallowing, convenience for traveling, or personal preference regarding taste and texture. Also, evaluate the quantity of vitamin B12 to determine how long it will last based on your daily requirements.

    • Quality and manufacturing

      Quality is paramount when selecting vitamin B12 supplements. Look for products manufactured under strict quality control guidelines and those that have undergone third-party testing for purity and label accuracy. Certifications from recognized bodies can be a reliable indicator of a high-quality product. Additionally, consider the manufacturer's reputation and transparency in their production processes.


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    How and when should you take vitamin B12 for maximum absorption?

    To get the most out of your vitamin B12 supplement, it's crucial to consider the timing and method of consumption. The following dos and don'ts offer guidance on optimizing absorption, efficiently supporting your health and wellness, and minimizing potential discomfort.


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      Speak with your doctor before taking any supplements.

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      Stick to the dosage instructions on the packaging.

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      Enhance absorption and reduce gastrointestinal discomfort by taking B12 with meals.

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      Regularly check your B12 levels, especially if you're at risk of deficiency or taking high doses.


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      Vitamin B12 should not be taken simultaneously with tetracycline, as it hinders the absorption and effectiveness of the antibiotic.

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      Avoid taking more than the recommended amount without medical advice.

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      Don't assume all supplements are equal; Different forms of B12 have different absorption rates; consult your doctor to choose the right one.

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      Don't rely solely on supplements; Aim to get B12 from natural food sources unless dietary restrictions apply.

    Who should take vitamin B12?

    Taking vitamin B12 supplements has its potential benefits, but it may not be for everyone.

    Recommended dosage

    Vitamin B12 plays an important role in many physiological processes, and getting the right dosage is essential for maintaining optimal health at different life stages. Here are the recommended dosages for vitamin B12 across various age groups.

    Side effects of excessive vitamin B12 consumption

    Oral vitamin B-12 is safe to take at recommended doses for healthy individuals. Since it is water-soluble, any excess amount will pass through the urine without causing harm. While taking more than the daily recommended amount is usually unnecessary, it is not harmful for most people.

    However, injectable vitamin B-12, which is used to treat significant deficiencies, can cause the following side effects in some individuals:

    • Digestive Issues: Consuming too much vitamin B12 may lead to digestive discomfort, such as diarrhea, nausea, or vomiting.
    • Skin Reactions: In rare cases, excessive B12 intake may cause skin rashes or acne-like symptoms.
    • Interaction with Medications: High B12 levels could interact with certain medications, emphasizing the importance of consulting a healthcare professional.
    • Allergic Reactions: Some people may experience allergic reactions to large doses, underscoring the need for cautious supplementation.

    Always consult your doctor

    If you're experiencing side effects, consult your healthcare provider. They may recommend a different vitamin B12 formulation or adjust your dosage. Balancing your vitamin B12 needs with any discomfort is crucial and should not be overlooked.

    Health made easy: your go-to resource for essential vitamins and supplements

    Frequently asked questions about vitamin B12 (FAQ)

    Our library of expert-authored articles covers just about every question you might have about vitamins, minerals, and supplements — along with some you might not have known you had.

    Final thoughts

    Vitamin B12 plays an important role in various bodily functions, and its deficiency can impact overall health. Obtaining sufficient B12 through diet, supplementation, or fortified foods is essential, especially for people at a higher risk of deficiency. Maintaining awareness of dietary sources, proper storage, and following recommended guidelines contributes to optimizing the benefits of vitamin B12 for a healthy lifestyle.

    Sources and references

    1. Vitamin B12 Deficiency - StatPearls - NCBI Bookshelf
    2. The B-complex vitamins related to energy metabolism and their role in exercise performance: A narrative review - ScienceDirect
    3. B Vitamins in the nervous system: Current knowledge of the biochemical modes of action and synergies of thiamine, pyridoxine, and cobalamin
    4. Vitamin B12 Status and Optimal Range for Hemoglobin Formation in Elite Athletes - PMC
    5. Vitamin B12—Multifaceted In Vivo Functions and In Vitro Applications - PMC
    6. Exploring the Immune-Boosting Functions of Vitamins and Minerals as Nutritional Food Bioactive Compounds: A Comprehensive Review
    7. A Systematic Review and Meta-Analysis of B Vitamin Supplementation on Depressive Symptoms, Anxiety, and Stress: Effects on Healthy and ‘At-Risk’ Individuals - PMC
    8. Vitamin B12 - Health Professional Fact Sheet
    9. Magnesium Supplement (Oral Route, Parenteral Route) Proper Use - Mayo Clinic
    10. Vitamin B12 deficiency & cognitive impairment in elderly population - PMC


    Stephanie Wright avatar

    Stephanie brings over 13 years of diverse nursing experience to the table, having honed her expertise in critical care, mental health, and utilization management. Her journey as a registered nurse across these various healthcare sectors underscores her adaptability and deep commitment to patient care.

    Fact checker

    Dr. Dimitar Marinov avatar

    Dr. Marinov has years of experience in scientific research and preventive and clinical medicine. His publications in peer-reviewed journals are on nutritional status, physical activity, and musculoskeletal disorders among adolescents.

    At VitaRx, we're not just passionate about our work — we take immense pride in it. Our dedicated team of writers diligently follows strict editorial standards, ensuring that every piece of content we publish is accurate, current, and highly valuable. We don't just strive for quality; we aim for excellence.

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    Get your personalized vitamin recommendations in less than 3 minutes.

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    Get your personalized vitamin recommendations in less than 3 minutes.

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