How Much Vitamin B12 Do You Really Need?

Introduction

Did you know that close to 40% of people may be deficient in vitamin B12 (1)? Did you also know that a vitamin B12 deficiency can mimic serious neurological disorders, leaving you feeling exhausted, foggy, and even depressed?

Vitamin B12 isn’t just another nutrient—it’s a non-negotiable for energy, brain function, and long-term health. The problem? Many of us don’t get enough, and the body’s ability to absorb it is shockingly inefficient.

So, who’s most at risk for vitamin B12 deficiency, and how much do you really need? What’s the best form to take, and why do many supplements provide 200% or more of the daily value? Below, we clear up the confusion so you can feel confident about your vitamin B12 intake and your decision to supplement.

What Makes Vitamin B12 So Important?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin critical for:

Energy Production: B12 helps your body convert carbohydrates, proteins, and fats into usable energy (2).

Red Blood Cell Formation: B12 helps prevent megaloblastic anemia, a condition that causes fatigue and weakness (3).

Brain Health: B12 supports cognitive function and protects the nervous system (4).

The three main sources of B12 are 1. animal-based foods such as meat and dairy products, 2. fortified foods, and 3. supplements (5).

Here’s the catch: our bodies can’t produce vitamin B12. This means that we rely entirely on food or supplements to meet our daily needs.

Who is Most at Risk for Vitamin B12 Deficiency?

Deficiency is far more common than most people realize. Groups at the highest risk include:

1. Vegans and Vegetarians: Since B12 is naturally found only in animal-based foods, plant-based diets are inherently low in this nutrient. One study discovered that about 60% of vegetarians are B12 deficient (6). The lack of vitamin B12 in a vegan and vegetarian diet can have serious health consequences. Read more about the benefits and risks of a plant-based diet here.

Learn more about the plant-based essentials vegan multivitamin designed to target common nutrient deficiencies that can occur as a result of a vegan or plant-based diet.

2. Adults Over 50: As we age, our ability to absorb B12 from food decreases because our bodies produce less stomach acid (7).

3. Pregnant and Breastfeeding People: B12 needs increase during pregnancy and lactation because it is essential for the proper growth and development of the baby’s brain and nervous system (8).

4. People with Gastrointestinal Disorders: Conditions like pernicious anemia, Crohn’s disease, and celiac disease can impair the body’s ability to absorb B12 due to damage in the lining of the stomach (9).

Symptoms of deficiency can range from mild to severe and include:

• Chronic fatigue and weakness
• Brain fog and poor memory
• Numbness or tingling in the hands and feet
• Mood disturbances like irritability or depression

If left untreated, B12 deficiency can lead to permanent nerve damage.

How Much Vitamin B12 Do We Really Need?

The Recommended Dietary Allowance (RDA) for B12 varies by age and life stage, but on average, adults should get 2.4 micrograms/daily (10).

However, due to absorption inefficiencies in B12, most people need much higher doses from supplementation to achieve optimal B12 levels. This is why B12 supplements typically contain doses far exceeding the Daily Value (DV): the answer lies in how inefficiently the body absorbs B12, where roughly 1–2% of B12 is absorbed (11). This means that from a 500 mcg vitamin B12 supplement, your body absorbs only about 5–10 mcg.

This explains why supplements often list doses of 150–500% of the Daily Value: the higher the dose, the more you absorb. Any excess B12 is water-soluble and gets excreted in the urine.

Supplementing with B12

Not all B12 supplements are created equal. There are three primary supplemental forms:

1. Cyanocobalamin:
• A synthetic form commonly used in fortified foods and supplements
• Affordable and stable but requires conversion in the body into active forms of B12
2. Methylcobalamin:
• A naturally occurring, active form of B12 that is more readily absorbed and retained by the body
• Ideal for people with poor absorption or impaired conversion pathways (e.g., MTHFR gene mutations)
3. Adenosylcobalamin:
• Another active form of B12, stored in the mitochondria, where it supports cellular energy production
• Often combined with methylcobalamin

If you’re pregnant, breastfeeding, vegan/vegetarian, or have malabsorption issues, then you should definitely consider supplementing with vitamin B12 since your risk of deficiency is much higher.

The Best Form to Take: For most people, methylcobalamin is the preferred option due to its superior absorption and bioavailability.

The plant-based essentials contains vitamin B12 in the form of methylcobalamin, the most bioavailable form, and is designed for vegans and vegetarians looking to optimize their plant-based diet. Shop our vegan multivitamin here.

Conclusion

Vitamin B12 is vital for energy, brain function, and long-term health, yet deficiencies are incredibly common. Because absorption is inefficient, relying solely on food—even fortified options—can leave you at risk. Supplementing with the right form and dose of B12 ensures your body gets what it needs.

References: 

1. Tucker KL, Rich S, Rosenberg I, Jacques P, Dallal G, Wilson PW, Selhub J. Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring study. Am J Clin Nutr. 2000 Feb;71(2):514-22. doi: 10.1093/ajcn/71.2.514. PMID: 10648266.
2. Yamada, K. (2013). Cobalt: Its Role in Health and Disease. In: Sigel, A., Sigel, H., Sigel, R. (eds) Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences, vol 13. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-7500-8_9
3. Krzywański J, Mikulski T, Pokrywka A, Młyńczak M, Krysztofiak H, Frączek B, Ziemba A. Vitamin B₁₂Status and Optimal Range for Hemoglobin Formation in Elite Athletes. Nutrients. 2020 Apr 9;12(4):1038. doi: 10.3390/nu12041038. PMID: 32283824; PMCID: PMC7230602.
4. Wu F, Xu K, Liu L, Zhang K, Xia L, Zhang M, Teng C, Tong H, He Y, Xue Y, Zhang H, Chen D, Hu A. Vitamin B₁₂Enhances Nerve Repair and Improves Functional Recovery After Traumatic Brain Injury by Inhibiting ER Stress-Induced Neuron Injury. Front Pharmacol. 2019 Apr 24;10:406. doi: 10.3389/fphar.2019.00406. Erratum in: Front Pharmacol. 2021 Apr 12;12:598335. PMID: 31105562; PMCID: PMC6491933.
5. Shipton MJ, Thachil J. Vitamin B12 deficiency - A 21st century perspective . Clin Med (Lond). 2015 Apr;15(2):145-50. doi: 10.7861/clinmedicine.15-2-145. PMID: 25824066; PMCID: PMC4953733.
6. Milton G.Crane, Clyde Sample, Shari Patchett &  D. Register (1994) Vitamin B₁₂ Studies in Toal Vegetarians (Vegans), Journal of Nutritional Medicine, 4:4, 419-430, DOI: 10.3109/13590849409003591
7. Ryan-Harshman M, Aldoori W. Vitamin B12 and health. Can Fam Physician. 2008 Apr;54(4):536-41. PMID: 18411381; PMCID: PMC2294088.
8. Wahbeh F, Manyama M. The role of Vitamin B12 and genetic risk factors in the etiology of neural tube defects: A systematic review. Int J Dev Neurosci. 2021 Aug;81(5):386-406. doi: 10.1002/jdn.10113. Epub 2021 Apr 22. PMID: 33851436.
9. Weisshof R, Chermesh I. Micronutrient deficiencies in inflammatory bowel disease. Curr Opin Clin Nutr Metab Care. 2015 Nov;18(6):576-81. doi: 10.1097/MCO.0000000000000226. PMID: 26418823.
10. Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington (DC): National Academies Press (US); 1998. 9, Vitamin B12. Available from: https://www.ncbi.nlm.nih.gov/books/NBK114302/
11. Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood. 2008 Sep 15;112(6):2214-21. doi: 10.1182/blood-2008-03-040253. Epub 2008 Jul 7. PMID: 18606874; PMCID: PMC2532799.