Vitamin B12 Deficiency: Symptoms, Causes & Treatment

Vitamin B12 deficiency is usually suspected when blood levels are below 200 to 250 pg/mL, especially when symptoms are present. Vitamin B12 levels are generally considered normal when they are between 160 and 950 pg/mL, although this range can vary by lab.

Vitamin B12 deficiency can cause fatigue, shortness of breath, pale skin, tingling, numbness and memory changes. Low levels can also lead to B12 deficiency anemia, and in children, they can cause growth delays and affect development.

Vitamin B12 deficiency may be caused by low B12 intake, digestive conditions, bariatric surgery, pernicious anemia, certain medications or excessive alcohol intake. Treatment depends on the cause and may involve B12 injections, oral supplements and eating more foods that contain or are fortified with vitamin B12.

Neurological symptoms

Tingling, numbness or loss of sensitivity in the hands, legs or feet can be a sign of vitamin B12 deficiency. According to the NIH Office of Dietary Supplements, vitamin B12 is needed for healthy red blood cell formation and normal development, myelination, and function of the central nervous system.

Low vitamin B12 levels can also cause memory loss, confusion, eye twitching and, in some cases, changes in balance or coordination.

General symptoms

Vitamin B12 deficiency symptoms may also include:

• Fatigue and weakness

• Palpitations

• Shortness of breath

• Mouth and tongue sores

• Loss of appetite

• Pale skin

• Vision changes

• Irritability

In children, vitamin B12 deficiency can cause delays in growth and development. A lack of this vitamin can also cause megaloblastic anemia, a type of anemia where the bone marrow produces red blood cells that are larger than normal.

Confirming a diagnosis

Vitamin B12 deficiency is diagnosed by a healthcare provider based on symptoms, medical history, eating habits, and blood test results.

To confirm the diagnosis, a healthcare provider may order blood tests, including a complete blood count (CBC) to evaluate red blood cells and hemoglobin, and a vitamin B12 blood test.

If poor absorption is suspected, additional tests, including an endoscopy, may be recommended to look for conditions such as Crohn's disease or celiac disease.

Common causes

Vitamin B12 deficiency can have several causes, including:

• Low vitamin B12 intake: Low intake of foods that contain or are fortified with vitamin B12 can cause a deficiency.

• Digestive conditions: Digestive conditions, such as Crohn’s disease and celiac disease, can prevent vitamin B12 from being absorbed efficiently.

• Bariatric surgery: Depending on the type of bariatric surgery, the size of the stomach or intestine may be reduced, which can decrease vitamin B12 absorption.

• Pernicious anemia: Pernicious anemia is a type of anemia that reduces the production of intrinsic factor, which is a protein needed for vitamin B12 absorption.

• Use of certain medications: Some medications, such as proton pump inhibitors, H2 antihistamines, metformin, cholestyramine and some antibiotics, can interfere with or reduce vitamin B12 absorption.

Excessive alcohol intake may also decrease vitamin B12 absorption.

Treatment options

Treatment for vitamin B12 deficiency depends on the underlying cause. It may include B12 injections, oral supplements, and increasing intake of foods that contain or are fortified with vitamin B12.

1. Vitamin B12 injections

Vitamin B12 can be given as intramuscular injections, most commonly as cyanocobalamin or hydroxocobalamin. According to the NIH Office of Dietary Supplements, injectable vitamin B12 is typically used to treat deficiency caused by pernicious anemia, malabsorption conditions, or severe vitamin B12 deficiency.

A common treatment regimen is 1,000 mcg of intramuscular vitamin B12 once a week for about four weeks, followed by 1,000 mcg once a month to maintain normal vitamin B12 levels. The dosage and treatment schedule may vary depending on the underlying cause and should be determined by a healthcare provider.

Read more about B12 injections and when they are recommended.

2. Supplements

Vitamin B12 deficiency caused by low dietary intake may be treated with oral vitamin B12 supplements.

Vitamin B12 supplements should be taken as prescribed by a healthcare provider, especially by people with polycythemia, an allergy to cobalt or cobalamin, or those recovering from surgery.

3. Diet

Increasing intake of vitamin B12 foods is mainly recommended for people who do not get enough B12 from their usual diet. Vitamin B12 is found in foods such as beef, fish, eggs, and milk, as well as in fortified products.