Vitamin B12 deficiency anemia

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at October 29, 2016
StartDiseasesVitamin B12 deficiency anemia

Vitamin B12 deficiency anemia occurs when the body does not have enough vitamin B12 to form healthy red blood cells. Without enough red blood cells, the body suffers a chronic oxygen deficiency, which leads to symptoms like constant fatigue, dizziness, and disorientation.


Definition & Facts

Vitamin B12 plays a critical role in the human body by providing nutrients to create red blood cells. Red blood cells carry oxygen throughout the bloodstream; without oxygen, none of the body's systems can work properly and a host of symptoms occur.

Vitamin B12 deficiency, or hypocobalaminemia, affects approximately 40 percent of people in the United States per year, but it is easily treatable and can resolve within months provided it has not inflicted severe nerve damage. Regular consumption of B12 supplements or food containing the vitamin can counteract the effects over time and allow the person to lead a better quality of life.

To diagnose this condition, the patient needs to submit to a full medical exam to rule out other potential causes of symptoms. Blood tests during a physical examination can also reveal possible issues developing.

Symptoms & Complaints

Many symptoms of vitamin B12 deficiency are often mistaken as normal parts of the aging process, but this is not necessarily true. The most prominent symptom of vitamin B12 anemia is fatigue, but a host of other symptoms can occur, including diarrhea, constipation, loss of appetite, bleeding gums and a swollen tongue. Due to loss of appetite, the person can also experience weight loss.

Over time, these symptoms worsen as B12 deficiency takes its toll on the body. Eventually, it can result in neurological symptoms including difficulty focusing, tingling hands and feet, difficulties with balance, gait abnormality, increased irritability, and memory loss.

Weak muscles and decreased energy are also symptoms that manifest with the absence of enough vitamin B12, as is dementia in the elderly.


The most common cause of B12 deficiency is not having enough food in the diet that contain it; these include red meat, poultry, eggs, and dairy products as well as nutritional supplements. A person over 14 years old needs at least 2.4 micrograms of vitamin B12 per day.

Certain conditions can prevent the body from being able to digest B12, such as alcoholism, atrophic gastritis, immune system disorders, or celiac disease. This condition does not manifest instantly; it takes weeks or months of chronic deficiency.

Certain conditions can also cause a person to lack the ability to absorb B12 due to a lack of intrinsic factor, an enzyme that breaks down the vitamin and absorbs it into the bloodstream. When the reason for a person's vitamin B12 deficiency anemia is lack of intrinsic factor, the condition is called pernicious anemia though sometimes this term is used interchangeably with vitamin B12 deficiency anemia.

Diagnosis & Tests

The main method of testing for hypocobalaminemia is a complete blood count. The physician takes a sample of blood and tests the red blood cell count against a healthy level for the patient's age, weight, and other factors. Should the red blood cell count be low, the sample also undergoes a test for folate or folic acid content because vitamin B12 and folate deficiency or folate-deficiency anemia can occur at the same time. This blood test can be administered during a routine physical checkup or as part of a specific battery of tests.

Subsequent examinations can determine the cause, such as the Schilling test. This involves ingesting radioactive B12 to determine whether the body absorbed it, then taking more B12 combined with intrinsic factor, the compound in the body that absorbs and breaks down vitamin B12. The lack of intrinsic factor can cause pernicious anemia and require regular injections of B12 combined with intrinsic factor.

Treatment & Therapy

The patient may meet with a dietician to come up with a diet plan that incorporates foods with more vitamin B12 and gradually increasing the amount of these foods that are consumed daily until the patient becomes accustomed to the change in diet. Some of these foods include eggs, poultry, dairy products, and fish such a rainbow trout.

If the patient has a vegetarian or vegan diet, other sources of food need to be considered. Another consideration is to watch folic acid intake and incorporate foods that include it. Some of these include leafy green vegetables, citrus fruits, and cereal specifically fortified with nutrients.

For patients with extreme dietary restrictions, it may be necessary to take daily supplements or injections; most people choose oral supplements wither via prescription or over-the-counter multivitamins. Over time, as the levels of B12 become replenished, the symptoms associated with the B12 deficiency anemia disappear. Injections combined with intrinsic factor may be necessary if the body cannot absorb B12 on its own.

Prevention & Prophylaxis

As with treatment, the most guaranteed way to prevent vitamin B12 deficiency anemia is to maintain a diet with healthy levels of B12 based on age, weight, and other dietary concerns, eat plenty of foods with vitamin B9 and vitamin C, and undergo regular checkups to watch for possible encroaching symptoms.

Substituting certain foods for unhealthy foods in the diet can have a host of other health benefits. For example, eating poultry instead of red meat decreases the risk of high cholesterol and increases the levels of B12 in the body. Leafy green vegetables, which provide folic acid and fiber, keep the body regular and also provide vitamin C. Eggs provide an alternate source of protein and work well with many breakfast dishes.

If dietary restrictions are in place due to lifestyle choices or food allergies, the person should consult his doctor about acquiring oral B12 supplements and taking them daily as indicated by instructions. He should also report any symptoms that appear and do not appear to have any other cause so the doctor can make an early diagnosis and begin treatment.

Those with a family history of pernicious anemia or similar conditions should take extra care. Women who follow a vegan diet and who are pregnant should take prenatal supplements to provide the developing fetus with the nutrients it needs to grow strong.