Vitamin B12 Deficiency

Symptoms include pale skin, dry lips, and fatigue.

Black man lying exhausted in bed with hands on head

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B12 is an essential vitamin, meaning it’s needed for your body to work properly. Taking in enough vitamin B12 is critical for overall health since the nutrient is necessary for processes involving the central nervous system, DNA, and red blood cells. Because your body can't make the vitamin on its own, you must obtain B12 through dietary sources or supplements.

However, it's estimated that 6% of the US population younger than 60 years is deficient in B12. Deficiency rates are much higher in specific populations, including people older than 60 and those taking certain medications, like the blood sugar-lowering medication metformin.

Vitamin B12 deficiency can have a big impact on the body. But the deficiency is something that can be caught and treated—or possibly prevented altogether.

How Much B12 Do You Need?

B12 needs change throughout your life. Like most other nutrients, babies and children need less B12 on a daily basis than adults.

Here are the daily intake recommendations for B12, in micrograms (mcg):

  • Birth to 6 months: .4mcg
  • 7-12 months: .5mcg
  • 1-3 years: .9mcg
  • 4-8 years: 1.2mcg
  • 9-13 years: 1.8mcg
  • 14-18 years: 2.4mcg
  • 19 years or older: 2.4mcg

It's important to keep in mind that recommended daily allowances are based on amounts needed to avoid deficiency. This means that these recommendations aren't necessarily what the average adult needs to maintain optimal levels of B12.

For example, research suggests that to maintain healthy blood levels of B12, daily intakes should reach 5.94mcg for men and 3.78mcg for women aged 20 or older.

During pregnancy and breastfeeding, needs for most vitamins and minerals increase. Because B12 is involved in the proper fetal growth and development, pregnant people require 2.6mcg of B12 per day while people who are breastfeeding need 2.8mcg per day. However, some experts recommend that those who are breastfeeding take in more B12 than what's currently recommended to maintain optimal blood levels of the vitamin.

B12 deficiency during pregnancy can harm both the parent and the baby. Being deficient in B12 during this time is associated with adverse outcomes like developmental abnormalities in babies and preeclampsia, a dangerous condition characterized by high blood pressure.

What Causes a Vitamin B12 Deficiency?

Several factors can cause a vitamin B12 deficiency. Some factors are out of a person's control.

The three main causes of B12 deficiency are:

  1. Autoimmune issues: Pernicious anemia is a type of autoimmune condition that makes it difficult for the small intestine to absorb B12. This leads to low B12 levels.
  2. Malabsorption: Some people aren't able to effectively absorb B12 due to intestinal damage or surgery. For example, people who've had gastric bypass surgery or part of their bowel removed may be at risk for developing a B12 deficiency.
  3. Low dietary intake: Vitamin B12 is in foods from animals, such as fish, meat, poultry, eggs, and dairy. If you're not including enough B12-rich foods in your diet, you could become deficient in B12. The deficiency might be more common in those who have been following vegan diets and strict vegetarian diets for at least a few years.

The long-term use of certain medications has also been linked to B12 deficiency. The blood sugar-lowering medication metformin and acid reflux-treating proton pump inhibitors are two examples of medications that can interfere with B12 absorption and cause B12 deficiency.

Risk Factors

Some people are more likely to develop a B12 deficiency than others due to factors like age and underlying medical conditions. Plus, certain factors, like the use of some medications, can increase the risk of B12 deficiency.

Risk factors for B12 deficiency include:

Being Over the Age of 60

The risk for B12 deficiency increases with age. This is due to malabsorption and the loss of gastric intrinsic factor, a substance that is required for B12 absorption. It is believed that up to 20% of US adults over 60 years are deficient in B12.

Taking Certain Medications

Some medications, including metformin and proton pump inhibitors, negatively affect the absorption of B12. That’s why long-term use of these medications could lead to a B12 deficiency.

Having Certain Health Conditions

People with certain health conditions are more likely to develop a B12 deficiency. These conditions include inflammatory bowel disease (IBD) and celiac disease. These diseases can make it harder for B12 to be absorbed.

Following a Vegan Diet

Because B12 is concentrated in animal foods like meat and fish, people who are following a vegan or vegetarian diet may be more likely to become deficient in B12. The risk is more so for people who’ve followed such a diet for at least three years. However, there are supplements and non-animal sources of B12, such as fortified cereal, that can prevent the deficiency for these groups.

Undergoing Certain Surgeries

Surgeries like gastric bypass, ileal resection (the removal of the end of the small intestine and the start of the colon), and gastrectomy (removal of part or all of the stomach) impact the body's ability to absorb B12.

Being Pregnant or Breastfeeding

Needs for B12 increase during pregnancy and breastfeeding, which puts pregnant and breastfeeding people at a higher risk for developing low B12 levels.

Abusing Alcohol or Drugs

Research shows that alcohol abuse and the use of certain drugs, such as methamphetamine, can increase the risk for B12 deficiency. This can be caused by poor dietary intake and decreased B12 absorption.

B12 Deficiency Symptoms

Some of the most common symptoms of B12 deficiency are vague, so deficiency can go undetected in many people. This is why it's essential to get bloodwork to assess B12 levels if you think you might have a deficiency.

The most common symptoms of B12 deficiency are: 

  • Fatigue
  • Pale skin
  • Pale conjunctiva (the tissue that lines the inside of your eyelids)
  • Breathlessness when engaging in activity
  • Dry lips 

An inflamed tongue (glossitis) can be another sign of B12 deficiency.

A B12 deficiency can also cause neurological symptoms like:

  • Dizziness
  • Memory impairment
  • Headaches
  • Tingling in the extremities
  • Difficulty walking

B12 deficiency can lead to more severe symptoms like neurological damage, which can be irreversible if left untreated.


B12 deficiency is diagnosed through blood testing such as a complete blood count, which should include testing of the serum B12 and folate levels. A healthcare provider may order other lab tests as well, including tests to measure methylmalonic acid and homocysteine levels—two measurements that can help diagnose a B12 deficiency.

People with serum B12 levels below 200 picograms per milliliter (pg/mL) are considered deficient. Those with serum B12 levels between 200 and 300 pg/mL are considered to be borderline deficient or to have low levels of B12. Up to 40% of people in Western populations have borderline B12 levels.

Even though levels above 300pg/mL are considered normal, people with low-normal levels may still experience symptoms of B12 deficiency.

If you're diagnosed with a B12 deficiency or have low-normal B12 levels, your healthcare provider will recommend a treatment plan specific to your needs.

B12 deficiency shares symptoms with other serious conditions and diseases, so it's important that you never self-diagnose and always reach out to a healthcare provider to undergo appropriate testing to rule out a potential deficiency.


If it's found that you have low or deficient B12 levels, your healthcare provider might recommend either oral B12 supplementation or B12 injections.

Your healthcare provider can also help manage any underlying health condition that may be causing your B12 deficiency.

Some people, like those who have inadequate dietary intake of B12, can increase their B12 levels by taking oral B12 supplements like sprays, capsules, or lozenges. However, for people who can't properly absorb B12 because of a medical condition or a past surgery, B12 injections are recommended.

Dosing and duration will vary depending on the level of deficiency and the underlying cause.

Dietary supplements are minimally regulated by the FDA and may or may not be suitable for you. The effects of supplements vary from person to person and depend on many variables, including type, dosage, frequency of use, and interactions with current medications. Please speak with your healthcare provider or pharmacist before starting any supplements.


Even though some causes of B12 deficiency aren't something that you can prevent, most people can maintain optimal B12 levels by eating foods that contain B12 or by supplementing their diet with B12.

If you're interested in supplementing with B12, it's a good idea to have your healthcare provider check your B12 levels beforehand. Then, ask them for advice on dosing to make sure you're taking appropriate amounts of B12.

Vitamin B12 is found in multivitamins as well as in B-complex and B12-only supplements. Multivitamins generally contain lower amounts of B12 than supplements that contain only B12.

Most B12-only supplements contain between 500-1,000 micrograms per dose. B12 supplements are generally considered safe, even at very high doses. This is because the body doesn't store it in excess amounts and excretes whatever it doesn't need in the urine.

In fact, there's no set tolerable upper intake level—the maximum daily intake of a nutrient unlikely to cause harm—for vitamin B12 due to its low potential for toxicity.

It's important to note that some forms of B12 are more effective for raising B12 levels than others. Research shows that natural forms of B12, such as methylcobalamin, may be more effective for increasing B12 levels compared to cyanocobalamin, which is a synthetic form of B12.

Best Vitamin B12 Foods

If you're concerned you're not getting enough B12 in your diet, try increasing your intake of the following B12-rich foods:

  • Cooked beef liver 
  • Cooked clams without the shell
  • Fish like salmon and tuna
  • Dairy products like yogurt and cheddar cheese
  • Eggs
  • Poultry like turkey

B12 is mostly concentrated in animal foods, but it can be found in some plant-based foods like fortified products. If you're following a plant-based diet that contains little or no animal products, try incorporating plenty of fortified foods in your diet to meet your B12 needs.

A few plant-based sources of B12 are:

A Quick Review

B12 deficiency can be caused by a number of factors, including medical conditions, medication use, and low dietary intake of the vitamin.

Being deficient in B12 can cause a range of vague symptoms like fatigue and pale skin. If left untreated, the deficiency can seriously impact health.

Although most people can maintain optimal B12 levels by regularly consuming B12-rich foods like fish, eggs, and yogurt, some people may need to take B12 supplements or get B12 injections to treat and prevent deficiency.

If you're concerned that you may be low or deficient in B12, make an appointment with a healthcare provider. They can order blood work that can rule out a potential deficiency and give you treatment recommendations based on your current B12 levels.

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