An overview of Vitamin B12

Vitamin B12 (also called cobalamin) is a water-soluble vitamin. It is an essential nutrient that the body needs to carry out important functions in the body, such as red blood cell production, DNA synthesis, and maintaining a well-functioning nervous system, among others. Cyanocobalamin is the man-made version of B-12.

How Much Vitamin B12 Do I Need?

Adults need 2.4 micrograms (mcg) of vitamin B12 a day. The human body does not make vitamin B12. Therefore, you need to get it from your diet (food sources) or dietary supplements in order to make enough red blood cells and other important functions. Vitamin B12 is absorbed from food in the terminal ileum (the last part of the small intestine).

What Happens When Your B12 Is Low?

Many organs in the body are affected when B12 is low. Not enough vitamin B-12 can affect the body’s ability to function properly. Signs and symptoms of vitamin B12 deficiency can include fatigue, pale skin, headaches, shortness of breath, fast heartbeat, gastrointestinal issues, mouth inflammation, paresthesias (abnormal sensations), decreased cognitive ability, depression, muscle weakness, imbalance and incoordination, vision problems, and erectile dysfunction.

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Common Signs and Symptoms of Vitamin B12 Deficiency

Fatigue

If you’re deficient in vitamin B12, your body can’t make enough healthy red blood cells. As a result, oxygen delivery to various organs and tissues is affected. A lack of healthy red blood cells can make you feel tired with weak muscles. Indeed, fatigue is one of the first signs of vitamin B12 deficiency. You can develop this symptom even when your B12 levels are only borderline low.

Pale or Yellow Skin

Pale skin may indicate a vitamin B12 deficiency and occurs due to a lack of healthy red blood cells. B12 deficiency can also lead to the destruction of immature red blood cells in the bone marrow, which can cause jaundice (yellowing of the skin and whites of the eyes). Jaundice occurs due to high bilirubin levels (a waste material created when the body breaks down RBCs).

Headaches

One of the most common symptoms of B12 deficiency is headaches. Studies have found that people who experience migraines are more likely to have low B12 levels than people with no migraine history. Further research is needed to determine whether eating foods rich in vitamin B12 or taking supplements can improve headaches.

Fast Heart Rate

People with a B12 insufficiency or deficiency lack enough healthy red blood cells. To make up for this, the heart may beat faster in an attempt to push more blood to the body more quickly and get enough oxygen to reach all the organs.

Shortness of Breath

B12 deficiency anemia can cause a person to feel short of breath. This is believed to be due to fewer red blood cells and a fast heartbeat. If you are experiencing trouble breathing, you should see a healthcare professional right away.

Gastrointestinal Symptoms

A B12 deficiency may cause symptoms such as bloating, gas, nausea, diarrhea, constipation, decreased appetite, and weight loss. It is believed these symptoms occur because the digestive tract does not get enough oxygen due to a lack of red blood cells.

Mouth Pain and Inflammation

A deficiency of vitamin B12 or other nutrients can cause inflammation and pain of the tongue (the medical term is glossitis). Sores and inflammation can also develop inside the mouth (stomatitis). It is common for people with B12 deficiency anemia to have glossitis and stomatitis. These can be signs of an early B12 deficiency or other nutritional deficiencies like folate, vitamin B2 (riboflavin), and vitamin B3 (niacin) deficiency.

Paresthesias

The medical term paresthesias refers to pins and needles or a burning sensation that typically occurs in the hands and feet. This symptom is common in people with a B12 deficiency.

However, paresthesias is also a common symptom of nerve damage caused by high blood sugar in people with diabetes — this is called diabetic peripheral neuropathy. Therefore, numbness and pain in the extremities from vitamin B12 deficiency can be mistaken for peripheral neuropathy in people with diabetes. Also, people with diabetes who take a medication called metformin are at a higher risk of developing B12 deficiency because this medication can reduce B12 absorption. If you take metformin regularly, talk to your health professionals about getting screened for vitamin B12 deficiency.

Depression

Vitamin B12 is necessary for the proper functioning of the brain. A deficiency of this vitamin can impact mental health. Studies show that B12 deficiency is linked to an increased risk of developing depressive symptoms, mood disorders, and psychosis. One theory is that mental health problems are caused by high homocysteine levels (vitamin B12 is needed to break down this chemical).

Mental Impairment

Low B12 levels can worsen mental function, especially in older adults. This can manifest as brain fog, difficulty concentrating, and difficulty completing tasks.

Other Signs and Symptoms of B12 Deficiency

In addition to the above, a vitamin B12 deficiency may cause the following symptoms:

Muscle weakness and muscle cramps.
Impaired balance and coordination, trouble walking.
Erectile dysfunction.
Vision problems due to optic nerve damage.

Serious Indicators of Vitamin B-12 Deficiency

Severe vitamin B12 deficiency can cause signs and symptoms such as

Yellow skin
Weak muscles
Numb or tingly hands or feet
Trouble walking
Severe joint pain
Increasing shortness of breath
Incontinence
Weight loss
Irritability
Lack of smell and taste sensations
Memory loss
Paranoia
Delusions
Deep depression

What Does B12 Fatigue Feel Like?

B12-related fatigue can feel like being tired all the time, despite getting enough rest and sleep. It can include extreme tiredness or exhaustion that prevents you from doing activities of normal life. In addition, B12 deficiency-associated fatigue is often accompanied by other symptoms such as numbness and tingling, cognitive impairment (memory and concentration problems), mood swings (depression), skin changes (pale skin), shortness of breath, or fast heart rate.

What Are The Facial Signs of B12 Deficiency?

Pale or yellow skin is a common sign of B12 deficiency. In addition, a deficiency of vitamin B12 can cause facial signs such as hyperpigmentation (dark spots), vitiligo (white patches where skin loses color), or angular stomatitis (inflammation at the corners of the mouth).

What Is Vitamin B12 Deficiency Anemia?

Red blood cells carry oxygen to every part of the body. In people who have a vitamin B12 deficiency, the body cannot make enough healthy red blood cells. This condition is called vitamin B12 deficiency anemia. As a result, the tissues and organs in the body don’t get enough oxygen, leading to vitamin B12 deficiency symptoms.

Another B vitamin is folic acid (also called folate). Folate deficiency anemia, like vitamin B12 deficiency anemia, is also a type of megaloblastic anemia. In these types of anemias, the red blood cells don’t develop like healthy red blood cells. Instead, they are very large and oval-shaped. As a result, the bone marrow makes fewer red blood cells (RBCs), and sometimes, the RBCs die sooner than usual.

Reticulocytes are immature red blood cells. A low reticulocyte count can be a sign of B12 deficiency because the bone marrow cannot make red blood cells without B12.

Causes of Vitamin B12 Deficiency

Absorption Issues

Most of the foods that are rich in vitamin B12 are of animal origin. As a result, eating a restrictive diet, such as a strict vegetarian or vegan diet, can lead to B12 deficiency. In addition, people with gastrointestinal issues that prevent absorption of nutrients from the gut can develop vitamin B12 deficiency symptoms.

Medical Conditions, Surgeries, and Medications

Who Is At Risk of Vitamin B12 Deficiency?

Anyone can develop a vitamin B12 deficiency. However, some people are at greater risk:

People who eat a restrictive diet that does not contain enough B12.
Older adults (there is reduced stomach acid production with age, and acid in the stomach is necessary to absorb vitamin B12).
People with a family history of vitamin B12 deficiency.
Those with gastrointestinal tract problems who cannot absorb vitamin B12 properly.
Those taking certain medications that affect how you absorb vitamin B12.

Learn more about what causes vitamin B12 deficiency.

Diagnosing Vitamin B12 Deficiency

What Are Normal B12 Levels?

A serum B12 level above 300 picograms per milliliter (pg/mL) is considered normal.
B12 levels between 200 and 300 pg/mL are considered borderline low.
People with B12 levels below 200 pg/mL are called B12 deficient and are likely to have symptoms - this could be due to medicines, strict vegetarian diets, or medical conditions.

What is an Alarming B12 Level?

An alarming or concerning B12 level is below 200 picograms per milliliter (pg/mL).

Medical Tests and Evaluations

Vitamin B12 deficiency can be diagnosed with a blood test that measures the level of the vitamin in your blood. Your healthcare provider can also diagnose B12 deficiency based on your medical history and physical exam. They might also order a routine blood test like a complete blood count and additional blood tests. In some cases, a bone marrow biopsy may be necessary.

Differentiating from Other Conditions

Neurological signs and symptoms can be vitamin B12 deficiency associated or due to other causes such as:

Diabetic neuropathy
Pernicious anemia
Multiple sclerosis
Syphilis
Neurosyphilis
Human immunodeficiency virus (HIV)-associated vacuolar myelopathy
Toxic neuropathies
Tropical myeloneuropathy

Your healthcare provider can make a proper diagnosis based on your symptoms, medical history, physical exam, and laboratory test findings.

Treatment Options for Vitamin B12 Deficiency

Given that a deficiency of vitamin B12 can affect so many organs in the body, it’s important to seek treatment. People who are at a high risk of B12 deficiency, such as those who eat strict vegetarian diets, should talk to their healthcare professional about screening for this condition.

Dietary Supplements

Vitamin B-12 deficiency can be corrected by eating foods rich in B12 and taking dietary supplements, such as B12 supplements or multivitamins.

A standard multivitamin may be all that is needed to correct a mild vitamin B12 deficiency. If a serious deficiency is detected, it can be corrected with high-dose vitamin B12 pills or weekly shots.

What Food Is Highest In B12?

Good food sources of vitamin B12 include organic meats, beef, poultry, milk, shellfish, fish, eggs, dairy products, wheat germ, soybeans, fortified cereals, orange juice, oranges, and nutritional yeast.

Beef liver is the highest in B12. Three ounces of pan-fried beef liver contains 70 mcg of vitamin B-12, which is nearly 3,000% of the recommended daily intake of 2.4 mcg in adults. Other foods that are high in vitamin B12 include:

3 ounces cooked clams without shells: 17 mcg
3 ounces wild cooked oysters: 15 mcg
1/4 cup fortified nutritional yeast: 8 to 24 mcg
3 ounces Atlantic salmon or canned tuna: 2.5 mcg
1 cup 2% milk: 1.3 mcg

What Is The Fastest Way To Fix B12 Deficiency?

The fastest way to fix B12 deficiency is with B12 shots. Vitamin B12 injections are called hydroxocobalamin. They are intramuscular shots given daily initially and then monthly.

Vitamin B12 shots are particularly useful for people with severe vitamin B12 deficiency. B12 injections are also used to treat people with malabsorption (gastrointestinal conditions that prevent proper absorption of B12 from the gut), for example, people with atrophic gastritis (stomach inflammation) and intrinsic factor deficiency (pernicious anemia) or those who have undergone surgical procedures such as gastrectomy or small bowel resection (stomach or intestine removed), autoimmune diseases, etc.

However, people with normal intestinal absorption and mild to moderate B12 deficiency symptoms can take oral B12 supplementation (B12 and folic acid pills).

How Do You Prevent Vitamin B12 Deficiency?

Regular Health Check-Ups

Regular health check-ups and screenings can lead to early detection of vitamin B-12 deficiency and correction before serious health complications develop. The guidelines are for people at high risk to be screened with a routine blood test at least once a year.

Lifestyle Adjustments

You can reduce your risk of developing a B12 deficiency by eating animal products that are rich in this vitamin. If you are a vegetarian, include wheat germ, soybeans, fortified bread, cereals, and grains, or take a daily B12 supplement.

Common Questions About B12 Deficiency

What Is Vitamin B12 Not Responsible for?

According to Harvard Health Publishing, there is no solid scientific evidence that getting enough vitamin B12 can prevent health conditions like heart disease, Alzheimer’s disease, infertility, eczema, and fatigue. For example, while many people with Alzheimer’s disease are found to have low vitamin B12 levels, there is no improvement in cognitive function after supplementation with high doses of vitamin B12.

What Organ Is Affected By B12 Deficiency?

The organ that is most affected by B12 deficiency is the nervous system and brain. Vitamin b12 deficiency symptoms can include peripheral neuropathy (numbness and tingling in the hands and feet), problems with balance and coordination, memory loss, trouble concentrating, changes in mental status, and depression, among other symptoms.

What Are The Four Stages of B12 Deficiency?

The 4 stages of B12 deficiency are as follows:

Stage 1: Low levels of vitamin B12 on blood test, but no symptoms.
Stage 2: Decreased levels of B12 and metabolic abnormalities such as high homocysteine or methylmalonic acid (MMA) levels.
Stage 3: Low vitamin B-12 and neurological and psychological symptoms such as paresthesias, balance problems, confusion, and depression.
Stage 4: Macrocytic anemia (abnormally large red blood cells) seen on laboratory testing.

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