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Vitamin B12 Supplementation: An Overview

Sep 30, 2020
Vitamin B12 Supplementation: An Overview
The prevalence of vitamin B12 deficiency is approximately 6% in persons younger than age 60 and nearly 20% in those older than age 60 in both the United States and the United Kingdom.

Vitamin B12 is a water-soluble vitamin that is naturally found in some foods and added to others. Vitamin B12 supplementation is available in oral and injectable forms. You might be surprised by the statistics on B12 deficiency. The prevalence of vitamin B12 deficiency is approximately 6% in persons younger than age 60 and nearly 20% in those older than age 60 in both the United States and the United Kingdom (Hunt et al. 2014). In developing countries, the rate of B12 deficiency is even higher. Foods high in vitamin B12 include meats and dairy products such as fish, shellfish, organ meats, eggs, beef, and pork.

The Physiology Of Vitamin B12 Supplementation

Vitamin B12 comes in two forms that are active in human metabolism, methylcobalamin and 5-deoxyadenosylcobalamin (Institute of Medicine, 1998). Vitamin B12 is required to form red blood cells in the body, for proper neurological function, and for the synthesis of DNA (NIH, n.d). When reviewing the symptoms of B12 deficiency, you may notice that many of them are secondary to the effects of anemia and others to malfunctioning brain cells.

A lack of red blood cells or abnormally formed red blood cells can really impact your energy levels, motivation, ability to think clearly, and overall health. A deficiency of vitamin B12 supplementation and its effects on the nervous system can masquerade as several other diseases and disorders, making assigning an accurate diagnosis very challenging.

When bound to the food we eat, Vitamin B12 is released by hydrochloric acid in the stomach, along with an enzyme called gastric protease. When vitamin B-12 is added to food or taken as a supplement, it is already in a free form and does not need to be released. Once vitamin B-12 is free, it combines with intrinsic factor. Intrinsic factor is a glycoprotein secreted by specialized cells lining the stomach called parietal cells. The combined intrinsic factor-vitamin B12 is absorbed into the body in the ileum, which is the most distal part of the small intestine (NIH, n.d.).

How vitamin b12 supplementation is absorbed in the body

B12 Deficiency Associated With The Absorption Pathway

Studying the absorption pathway for vitamin B12 supplementation, you may note four possible impediments to absorbing adequate vitamin B-12.

  1. Hydrochloric acid and gastric proteases are necessary to separate vitamin B-12 from food. Those taking antacids to raise the pH of their stomach due to a history of indigestion or ulcers may be vitamin B-12 deficient.
  2. An autoimmune disorder can lead to the destruction of parietal cells, which means no hydrochloric acid or intrinsic factor production. This autoimmune condition is called pernicious anemia and is a cause of vitamin B-12 deficiency.
  3. Intrinsic factor can only bind to approximately 56% of a 1 mcg dose of vitamin B12, and absorption decreases dramatically at doses over 1-2 mcg (Carmel, 2008).
  4. Those with inflammatory bowel disorders or conditions that affect the distal small intestine’s inner lining may not absorb the intrinsic factor-B12 complex efficiently into the body.

Other groups of people at risk for B12 deficiency include:

  • Those taking high doses of folic acid as high levels of folic acid may mask vitamin B12 deficiency.
  • Older adults tend to produce less hydrochloric acid in their stomachs. This condition, called atrophic gastritis, affects 10-30% of the senior population (Institute of Medicine, 1998).
  • Those who have had stomach surgery may have a decreased number of cells to produce hydrochloric acid and intrinsic factor.
  • Those taking metformin for more than four months.
  • Vegans and vegetarians may have an inadequate intake of vitamin B12 in their diets.
  • Pregnant and lactating mothers who are strict vegetarians and their infants (NIH, n.d.).
  • People over age 75 are at increased risk due to inadequate intake of vitamin B12
  • Alcohol abuse increases B12 deficiency risk due to inadequate intake of the vitamin in the diet (Langan & Goodbred, 2017).
0-6 months0.4 mcg0.4 mcg
7–12 months0.5 mcg0.5 mcg
1–3 years0.9 mcg0.9 mcg
4–8 years1.2 mcg1.2 mcg
9–13 years1.8 mcg1.8 mcg
14+ years2.4 mcg2.4 mcg
Institute of Medicine (1998)

In the United States, the average intake is 3.4 mcg per day, which means that the average person who eats an omnivore diet is at low risk (Institutes of Medicine, 1998).

An omnivore diet can decrease the risk of vitamin B12 deficiency.

Symptoms Of Vitamin B12 Deficiency


  • Ringing in the ears
  • Tremors or an involuntary shaking of muscles
  • Numbness and tingling in the arms and legs
  • Confusion, memory problems
  • Muscle weakness
  • Unsteady gait
  • Difficulty with maintaining balance
  • Dizziness
  • A feeling that you need to move your legs at night
  • Vision, taste, or smell disturbances


  • Psychosis
  • Hallucinations
  • Depression
  • Mania
  • Anxiety
  • Irritability
  • Sleep disturbances


  • Insomnia
  • Weakened bones and fractures
  • Abnormal heart rhythms
  • Infertility
  • Weight loss
  • Stomach pain
  • Constipation
  • Appetite loss
  • Soreness of the mouth or tongue (Healton et al., 1991)
  • Megaloblastic anemia leading to difficulty breathing, weakness, pale skin color, fatigue, and jaundice (yellow color to the skin or eyes
Vitamin B12 Supplementation: An Overview

Contraindications And Concerns With Vitamin B12 Supplementation

If you have any of the following, speak with a health care provider before supplementing with vitamin B12 in any form:

  • An allergy to cyanocobalamin or cobalt
  • An inherited form of vision loss called Leber’s disease
  • Kidney or liver disease
  • Iron or folic acid deficiency
  • Any infection
  • Any medication or treatment that affects the bone marrow
  • Medications such as anti-seizure medications, chemotherapy medications, antibiotics, colchicine, bile acid sequestrants, H2 blockers, metformin, or proton pump inhibitors (Penn State Hershey, 2015).

Testing And Treating

Screening people for vitamin B12 deficiency is not usually recommended, but it should be done in those with risk factors or have symptoms consistent with vitamin B12 deficiency (U.S. Services Preventative Task Force, 2010). A blood test for vitamin B12 levels and a complete blood count to rule-out anemia start the evaluation. A level of vitamin B12 less than 150 pg per mL is diagnostic for deficiency. These levels must be evaluated by a health care professional since alcoholism, liver disease, and cancer can falsely elevate vitamin B12 levels. The risks and benefits of vitamin B12 deficiency are closely tied to folic acid, which may confound the clinical picture (Langan & Goodbred, 2017).

Vitamin B12 Supplementation: An Overview

Guidelines from the British Society of Haematology recommend treating those with an irreversible cause indefinitely and those with a reversible cause until the deficiency has resolved (Hunt, Harrington, & Robinson, 2014).

Purchasing B12 Injections

Purchasing B12 shots at home as a treatment for vitamin B12 deficiency can effectively manage and treat your condition. The injections are relatively easy and painless to administer, and you can do it all from the comfort of your own home. Vitamin B12 injections require a prescription. Several serious diseases can overlap with the symptoms of B12 deficiency, so it is essential that you receive an accurate diagnosis.

Once you’ve conferred with your doctor, and they have written you a prescription, it is essential to choose a high-quality B12 supplement to treat your deficiency. Invigor Medical provides high-quality medical treatment plans, with high quality medications.

Frequently Asked Questions

Is it OK to take 1000 mcg B12 daily?

Taking 1000 mcg of vitamin B12 daily is generally considered safe for most adults, as it exceeds the recommended daily intake. However, it’s advisable to consult with a healthcare professional before starting such a high dose to ensure it’s appropriate for your specific needs and health.

Is it worth taking vitamin B12 supplements?

The need for vitamin B12 supplements varies from person to person. It’s worth considering supplementation if you have a deficiency, are at risk of deficiency (e.g., due to dietary restrictions), or if recommended by a healthcare provider. For those with adequate dietary intake and no deficiency symptoms, supplements may not be necessary.

What is the best form of vitamin B12 to take?

The best form of vitamin B12 to take depends on individual preferences and needs. Common forms include cyanocobalamin and methylcobalamin. Cyanocobalamin is more stable and often used in supplements, while methylcobalamin may be preferred by some due to its potential for better absorption. Consult with a healthcare professional to determine the best form for your situation.

Can you take too much vitamin B12?

Vitamin B12 is considered safe in moderate to high doses, and there is a low risk of toxicity. However, extremely high doses taken regularly can lead to adverse effects. It’s important to follow recommended guidelines and consult a healthcare professional to avoid excessive intake, especially for individuals with certain medical conditions or medications that affect B12 absorption.

While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.

Vitamin B12 Supplementation: An Overview

Leann Poston, M.D.

Dr. Leann Poston is a licensed physician in the state of Ohio who holds an M.B.A. and an M. Ed. She is a full-time medical communications writer and educator who writes and researches for Invigor Medical. Dr. Poston lives in the Midwest with her family. She enjoys traveling and hiking. She is an avid technology aficionado and loves trying new things.


  • NIH. (n.d.). Vitamin B12.
  • Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press, 1998.
  • Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood.2008;112:2214-21.
  • Hunt A, Harrington D, & Robinson S. Vitamin B12 deficiency. BMJ. 2014;349g5226.
  • Langan, R. & Goodbred, A. (2017). Vitamin B12 Deficiency: Recognition and Management. Am Fam Physician.; 96(6):384-389.
  • U.S. Services Preventative Task Force. A-Z Topic Guide. (2010).
  • Healton EB, Savage DG, Brust JC, Garrett TF, Lindenbaum J. Neurological aspects of cobalamin deficiency. Medicine 1991;70:229-44.
  • Penn State Hershey. (2015). Vitamin B12 (Cobalamin).


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