What Happens When Your B12 Is Low—and How To Fix It (2024)

A vitamin B12 deficiency, or low B12, means you're not taking in or absorbing enough of the vitamin. B12 is an essential vitamin, meaning it's needed for your body to work properly. It's necessary for processes that involve the central nervous system, DNA, and red blood cells.

Symptoms of low B12 commonly include dry lips, fatigue, and pale skin. If left untreated, anemia, or a lack of red blood cells, and neurological damage may develop over time.

The number of people with vitamin B12 deficiency varies, but some evidence suggests that as many as 2% of people with anemia have the condition. Deficiency rates are much higher in specific populations, including people older than 60 and those who take certain medications like metformin.

Vitamin B12 deficiency can have a big impact on the body. Low B12 can be caught and treated or possibly prevented altogether. Your body can't make the vitamin on its own, so you must obtain B12 through dietary sources or supplements.

Signs and Symptoms of Vitamin B6 Deficiency

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.

Some of the first symptoms of B12 deficiency are similar to anemia and include dizziness, fatigue, headaches, and shortness of breath. Other common symptoms of B12 deficiency are:

What Causes Low B12?

Several factors can cause a vitamin B12 deficiency, and some are out of a person's control. The three main causes of B12 deficiency are:

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

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 (PPIs) can interfere with B12 absorption and cause a deficiency.

Risk Factors

Anyone can develop low B12, but some people have a higher risk than others. Risk factors that increase your likelihood include:

Age: The risk for B12 deficiency increases with age. This is due to malabsorption and the loss of gastric intrinsic factor, or a substance required for B12 absorption. Up to 20% of U.S. adults over 60 are deficient in B12.
Certain medications: Some medications, including metformin and PPIs, negatively affect the absorption of B12. Long-term use of these medications could lead to a B12 deficiency.
Health conditions: People with certain conditions are more likely to develop a B12 deficiency. These include inflammatory bowel disease (IBD) and celiac disease. These diseases can make it harder for B12 to be absorbed.
Pregnant or breastfeeding: Needs for B12 increase during pregnancy and breastfeeding. These needs put pregnant and breastfeeding people at a higher risk of developing low B12 levels.
Substance use disorder: Research has shown that alcohol use disorder 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.

Surgery: 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.
Vegan diet: B12 is concentrated in animal foods like meat and fish. People who follow 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. Some supplements and non-animal sources of B12, such as fortified cereal and nutritional yeast, can prevent the deficiency for these groups.

B12 deficiency is diagnosed through blood testing, such as:

Complete blood count (CBC): This test can measure the number of red blood cells you have. Low B12 levels can lead to anemia, or a lack of oxygen-rich red blood cells.
hom*ocysteine levels: High levels of this amino acid can indicate low B12 levels. Vitamin B12 helps break down hom*ocysteine.
Methylmalonic acid: Vitamin B12 helps regulate the amount of this substance in the body. High methylmalonic levels can indicate 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.

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

Treatments

If you're diagnosed with a B12 deficiency or have low-normal B12 levels, a healthcare provider will recommend a treatment plan specific to your needs. They might recommend dietary changes or oral B12 supplementation, but treatment likely depends on the underlying cause. You may require B12 injections, for example, if you're unable to absorb the vitamin.

Those who have inadequate dietary intake of B12 can take oral B12 supplements like sprays, capsules, or lozenges. Here are the daily intake recommendations for B12 in micrograms (mcg):

Birth to 6 months: 0.4 mcg
7 to 12 months: 0.5 mcg
1 to 3 years: 0.9 mcg
4 to 8 years: 1.2 mcg
9 to 13 years: 1.8 mcg
14 to 18 years: 2.4 mcg
19 years or older: 2.4 mcg

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. Some evidence suggests that daily intakes should reach 5.94 mcg for men and 3.78 mcg for women aged 20 or older to maintain healthy blood levels.

B12 is involved in proper fetal growth and development. Pregnant people require 2.6 mcg of B12 per day. Those who are breastfeeding need 2.8 mcg per day. Some experts recommend that those who are breastfeeding take in more B12 than what's recommended to maintain optimal blood levels.

A healthcare provider can also help manage any underlying health condition that may be causing your B12 deficiency. B12 injections are recommended for people who can't properly absorb B12 because of a condition or surgery. Dosing and duration will vary depending on the level of deficiency and the underlying cause.

The Food and Drug Administration minimally regulates dietary supplements. The effects of B12 supplements vary and depend on dosage, frequency of use, and interactions with current medications. Talk to a healthcare provider or pharmacist before starting any supplements.

Most people can maintain optimal B12 levels by eating foods that contain B12 or by taking a supplement. However, it's important to note that some forms of B12 are more effective for raising B12 levels than others. Research has shown that natural forms of B12, such as methylcobalamin, may be more effective in increasing B12 levels than cyanocobalamin, a synthetic form of B12.

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

Cooked beef liver
Cooked clams without the shell
Dairy products like yogurt and cheddar cheese
Eggs
Fish, including salmon and tuna
Fortified breakfast cereals, non-dairy plant milks like soy milk, and nutritional yeast
Tempeh
Turkey

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 to 1,000 mcg per dose.

B12 supplements are generally considered safe, even at very high doses. The body doesn't store it in excess amounts and excretes whatever it doesn't need in the urine. There's no set tolerable upper intake (TUI) level for vitamin B12 due to its low potential for toxicity. TUI is the maximum daily intake of a nutrient unlikely to cause harm.

Complications

If left untreated, low B12 levels can cause complications like:

Anemia: Vitamin B12 helps make red blood cells, which carry oxygen throughout the body. Low B12 levels can result in anemia, or a lack of red blood cells. Vitamin B12 deficiency anemia causes symptoms like fatigue and irritability.
Heart disease: Low B12 levels raise levels of hom*ocysteine acid, which can increase heart disease risk. Research has shown that hom*ocysteine acid can lead to atherosclerosis. This build-up of fatty substances in the arteries can cause heart attack and stroke.
Neurological damage: Vitamin B12 helps make myelin, which protects nerve cells. Low B12 levels can lead to neurological damage as a result. Symptoms include depression, memory problems, and numbness or tingling in the hands and feet.

B12 deficiency during pregnancy can harm both the parent and the developing fetus. Being deficient in B12 during this time is associated with adverse outcomes like developmental abnormalities. Pregnant people can also develop preeclampsia, or a type high blood pressure.

Signs and Symptoms of Vitamin C Deficiency

B12 deficiency can be caused by a number of factors, including conditions, medications, and low dietary intake of the vitamin. Being deficient in B12 can cause a range of vague symptoms like fatigue and pale skin.

Make an appointment with a healthcare provider if you're concerned that you may be low or deficient in B12. Most people can maintain optimal B12 levels by regularly consuming B12-rich foods like fish, eggs, nutritional yeast, yogurt, or fortified breakfast cereals. Some people may need to take B12 supplements or get injections to treat and prevent deficiency.