Vitamin B12 Deficiency
(Vitamin B12 Deficiency; Macrocytic Achylic Anemia)
Pronounced: Vite-ah-min bee-twelv di-fish-ens-ee
by Monique Kahn, MS, RD
Vitamin B12 helps in red blood cell formation, production of DNA, and function of the nervous system.
Vitamin B12 deficiency can occur when the body needs more vitamin B12 than it receives from the diet. Alternatively, the condition may occur when the body is unable to use vitamin B12 from the diet. A shortage of vitamin B12 can lead to anemia. Anemia occurs when levels of red blood cells are abnormally low and there is insufficient delivery of oxygen by red blood cells from the lungs to the cells of the body.
There are many causes of vitamin B12 deficiency, such as:
Risk Factors TOP
The following factors increase your chance of developing vitamin B12 deficiency:
The symptoms of pernicious anemia can vary from person-to-person. Symptoms may change or worsen over time.
Symptoms can include:
You will be asked about your symptoms and medical history. A physical exam will be done. Tests may include the following:
Talk with your doctor about the best treatment plan for you. Treatment options include the following:
Oral Vitamin B12 Supplement
This treatment consists of high doses of an oral vitamin B12 supplement.
Vitamin B12 Injections
The doctor may advise injections of vitamin B12 into a muscle. Injections of vitamin B12 may be given frequently at first. When blood tests show improvement, the injections may be given on a monthly basis.
Treatment with Antibiotics TOP
This type of medication may be needed in cases where bacterial overgrowth in the intestines exists. The bacteria compete with the body to absorb the vitamin B12 in the intestines.
Intranasal Vitamin B12 TOP
The doctor may advise a supplement of vitamin B12 that is placed in the nose.
To help reduce your chances of developing a deficiency of vitamin B12, take the following steps:
Family Doctor—American Academy of Family Physicians
National Institutes of Health Office of Dietary Supplements
College of Family Physicians of Canada
Food sources of vitamin B12. Dietitians of Canada website. Available at: https://www.dietitians.ca/Your-Health/Nutrition-A-Z/Vitamins/Food-Sources-of-Vitamin-B12.aspx. Accessed November 7, 2017.
Pernicious anemia. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T116294/Pernicious-anemia. Updated May 17, 2017. Accessed November 7, 2017.
Vitamin B12. American Association of Clinical Chemistry—Lab Tests Online website. Available at:
...(Click grey area to select URL)
Updated April 24, 2015. Accessed November 7, 2017.
Vitamin B12. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T233168/Vitamin-B12. Updated November 6, 2017. Accessed November 7, 2017.
Vitamin B12 deficiency. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T116899. Updated December 4, 2015. Accessed November 7, 2017.
Last reviewed November 2017 by EBSCO Medical Review BoardDianne Scheinberg Rishikof MS, RD, LDN
Last Updated: 12/20/2014
EBSCO Information Services is fully accredited by URAC. URAC is an independent, nonprofit health care accrediting organization dedicated to promoting health care quality through accreditation, certification and commendation.
This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.
To send comments or feedback to our Editorial Team regarding the content please email us at firstname.lastname@example.org. Our Health Library Support team will respond to your email request within 2 business days.