Key takeaways:
Vitamin B12 is needed for healthy blood cells, nerve cells, and DNA. Symptoms of vitamin B12 deficiency include anemia and neurological issues.
You can be deficient in vitamin B12 if you don’t get enough B12 in your diet or your gut can’t absorb it.
You can treat or manage vitamin B12 deficiency with supplements, injections, or nasal spray. A healthcare professional will determine the best treatment for your vitamin B12 deficiency, based on the cause.
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Vitamin B12 is an essential nutrient that does its job quietly and efficiently inside the body. Vitamin B12 helps to make new DNA and keep nerve and blood cells healthy. It also helps our cells break down proteins and fats for energy.
Most people get enough vitamin B12 in their diet and absorb it through the digestive system. But some diets and certain health conditions may lead to a deficiency of this important vitamin, especially as you get older.
What is vitamin B12?
Vitamin B12, also called cobalamin, is one of the B-complex vitamins. It’s not made by the body, so we need it in our diet. Vitamin B12 isn’t made by plants either. It’s found in animal products, in foods where B12 has been added, or in supplement form.
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Here’s how much vitamin B12 people need each day, based on factors like age and pregnancy:
Teens and adults: about 2.4 mcg
Pregnant people: around 2.6 mcg
Breastfeeding people: 2.8 mcg
Infants and children: 0.4 mcg to 1.8 mcg, depending on their age
Why vitamin B12 matters
Vitamin B12 is critical for many normal body functions that keep you healthy. Not having enough vitamin B12 can cause complications in multiple body systems. Vitamin B12 is essential for:
Making certain cells, especially red blood cells
Proper cell function
Cellular repair
Making and repairing DNA
Nerve health
Common symptoms of vitamin B12 deficiency
Let’s take a closer look at five common symptoms of vitamin B12 deficiency.
1. Anemia
Low B12 levels cause a kind of anemia, or low blood count. Sometimes, the blood cells become large, or macrocytic, before a person becomes anemic.
Symptoms of anemia might include:
Feeling tired or having low energy
Pale skin
Feeling short of breath, especially with movement
Having less of an appetite or losing weight without trying
Feeling dizzy or like you might faint
Some people with B12 deficiency also have mouth sores or a swollen, painful tongue.
2. Nerve damage
Vitamin B12 is also important for nerve cells to function. B12 deficiency can affect the central nervous system (the brain and spinal cord) or the peripheral nerves that go to the rest of the body.
Symptoms of nerve damage from B12 deficiency can include:
Tingling, or a pins-and-needles sensation
Depression, irritability, or confusion
Changes in vision
Problems with balance
3. Birth defects
Pregnant people need to have enough B12 as well as folate, or vitamin B9, which is also an essential vitamin. If not, the baby could be born with a neural tube defect. This happens when the brain or spinal cord develops incorrectly. Vitamin B12 is also present in breast milk. So, a breastfed baby whose mother has a low B12 level could have complications. These might include delayed development, slow weight gain, or anemia.
4. DNA damage
Cells need vitamin B12 to make new DNA. When cells can’t make or repair DNA, they start to divide incorrectly. Low B12 and folate levels play a role in DNA damage, which may lead to diseases like cancer. This may be why low vitamin B12 is thought to play a role in heart disease, stroke, and dementia. More research is needed to establish a direct relationship.
5. Mental sluggishness and mood changes
Low vitamin B12 and folate are linked to several mental health issues. The connection is likely because B12 and folate are both needed to produce neurotransmitters, repair DNA, and maintain nerve coverings. Low levels of B12 and folate can then lead to low levels of serotonin and dopamine and sluggish brain signals — all of which can affect your mood.
Research is ongoing in this field. Some of the mood symptoms of B12 deficiency include:
Depression
Anxiety disorders
Mental decline
Dementia
When should I seek care for vitamin B12 deficiency symptoms?
If you notice any physical symptoms of vitamin B12 deficiency, you’ll need to let a healthcare professional know right away. They’ll need to run some tests to see if vitamin B12 levels are the cause of your symptoms. It’s important to make the diagnosis quickly. If left untreated, low vitamin B12 levels can lead to serious neurological or physical effects.
What causes vitamin B12 deficiency?
The body stores extra vitamin B12 in the liver. So, it may take years for someone to develop symptoms from a B12 deficiency. But there are certain conditions and diets that put some people more at risk.
Not consuming enough
Most people in the U.S. consume enough vitamin B12. But you could be at risk for B12 deficiency if you follow a strict vegan or vegetarian diet without taking supplements.
Vitamin B12 comes from animal products like:
Eggs
Dairy products
Poultry
Fish
Meat
It’s added to some foods like cereals and nutritional yeast. Vitamin B12 is also present in breast milk and added to infant formula. The infants of pregnant or breastfeeding people who don’t get enough vitamin B12 are also at risk.
You can check a food’s nutrition label to see how much vitamin B12 has been added, or if it doesn’t occur naturally at all.
Not absorbing enough
Some people consume enough vitamin B12, but their body can’t absorb it. Reasons for this include having chronic illnesses that interfere with small bowel absorption or production of a protein called intrinsic factor. These can lead to B12 deficiency.
The longer the condition has been present, the greater the risk of B12 deficiency. Some health conditions, procedures, and behaviors that may affect B12 absorption include:
Weight-loss surgery or other surgery on the stomach and intestines
Low stomach acid, occurring with age or from taking medications to reduce stomach acid
Inflammation in the stomach or small intestine from gastritis, celiac disease, or Crohn’s disease
Pernicious anemia, an autoimmune condition where the stomach doesn’t make a protein that is needed to absorb B12
Taking metformin for diabetes, which may decrease B12 absorption
Drinking alcohol, which can interfere with the body’s ability to absorb enough B12 or the ability to use B12 effectively
Age
About 10% to 15% of people over age 60 have B12 deficiency. The underlying reason may be due to the increase in atrophic gastritis as you age. Atrophic gastritis is a condition where the stomach lining thins and loses some of its function. The stomach lining makes intrinsic factor, which is required for B12 absorption. So, loss of this function means less B12 is absorbed.
People in this age group may not have classic symptoms. B12 deficiency in older populations can be misinterpreted as early dementia, so testing and prompt treatment are important.
Chemotherapy
People receiving chemotherapy are at an increased risk of B12 deficiency. This is especially true for people with primary gastric and pancreatic cancers. Rates of B12 deficiency can reach close to 50% depending on age and the type of cancer.
People being treated for cancer may have elevated levels of B12, but they may not be able to use the vitamin effectively. This can lead to a functional deficiency. Functional B12 deficiency can lead to anemia and neurologic complications and true B12 deficiency. It’s important to look for the presence of deficiency symptoms even if you have elevated B12 levels.
How is B12 deficiency diagnosed?
A healthcare professional may do blood tests if you’re at risk for a vitamin B12 deficiency. A physical exam can provide clues, but you may not have any symptoms or obvious changes on an exam. Some of the blood tests used to diagnose B12 deficiency include:
Hemoglobin and hematocrit (RBC count): Low levels of both indicate anemia.
Mean corpuscular volume (MCV): Large red blood cells coupled with anemia (macrocytic anemia) suggest B12 deficiency.
Peripheral blood smear: This looks for large, pale red blood cells and abnormal looking white blood cells (hypersegmented neutrophils).
B12 level: Used to confirm B12 deficiency.
Folate (folic acid) levels: Folate deficiency can look like B12 deficiency.
Methylmalonic acid level (MMA) and homocysteine levels: MMA and homocysteine levels are elevated in B12 deficiency and can be used to differentiate B12 and folate deficiency.
Anti-intrinsic factor antibody test: A test to determine an autoimmune cause of B12 deficiency. Intrinsic factor is a protein that helps B12 get absorbed in the small intestine.
Not all of these tests may be necessary to make the diagnosis of B12 deficiency. Your healthcare team will determine which tests to order based on your medical history, physical exam, and results of other tests.
How do you treat B12 deficiency?
Depending on the severity and cause, there are oral, nasal, or injected forms of B12 treatment. If the B12 deficiency isn’t severe and is due to low intake, you can often treat it with an oral supplement. These are some examples of different treatment options:
Nutritional support: Including more B12 containing foods in the diet can improve deficiency in people with normal absorption and who don’t have autoimmune disease.
Oral B12 supplements: Oral supplements may be a good option for vegetarians who want to avoid animal sources. Make sure to choose a third party-certified product as many supplements on the market may not contain the labeled ingredient or dose.
Nasal spray B12: Nascobal is a prescription, once a week nasal spray that can bypass the need for B12 gut absorption. It’s an alternative to injections for people with absorption issues, but milder deficiency.
B12 injections: Severe B12 deficiency — especially if it’s caused by an absorption problem or autoimmune condition — is usually treated with B12 injections. This may be for a period of time, or it may be for life, depending on the condition.
If medications or alcohol are interfering with absorption, these should also be limited or stopped whenever possible.
How long does it take to recover from B12 deficiency?
After treatment, your blood count may start to improve after several days. Nerve damage may take longer to heal and could be permanent if it’s not treated within the first 6 months of symptoms.
How can I prevent vitamin B12 deficiency?
Not all forms of B12 deficiency can be prevented. But there are some things you can do to decrease your risk. These include:
Eating a balanced diet: This means including foods that are fortified with B12 or supplements
Drinking in moderation: This means 1 drink a day for women and 2 a day for men.
Getting screened: This is important if you take medications or have a condition that puts you at risk.
Can you take too much B12?
Vitamin B12 supplements are sometimes marketed as a way to boost energy. But if you have normal levels in your body already, taking more won’t improve your energy level. Although B12 is generally considered safe, taking large amounts of supplements may have unwanted side effects.
Side effects can include:
Frequently asked questions
Injections are the fastest way to fix B12 deficiency. However, injections aren’t always the best option. Many people can use oral supplements or the prescription nasal spray to replace B12 if they don’t have absorption problems or an autoimmune condition.
Facial signs of B12 deficiency vary depending on duration, degree of deficiency, and cause. Pale skin, mouth or lip ulcers, and vitiligo are possible signs. Rarely, darkening of the skin (hyperpigmentation) can also happen.
Vitamin B12 deficiency can lead to several serious medical conditions if left untreated. Among these are:
Megaloblastic anemia
Paraesthesia (tingling of the hands and feet)
Subacute combined degeneration (SCD) of the spinal cord and brain white matter
Other less common diseases
Injections are the fastest way to fix B12 deficiency. However, injections aren’t always the best option. Many people can use oral supplements or the prescription nasal spray to replace B12 if they don’t have absorption problems or an autoimmune condition.
Facial signs of B12 deficiency vary depending on duration, degree of deficiency, and cause. Pale skin, mouth or lip ulcers, and vitiligo are possible signs. Rarely, darkening of the skin (hyperpigmentation) can also happen.
Vitamin B12 deficiency can lead to several serious medical conditions if left untreated. Among these are:
Megaloblastic anemia
Paraesthesia (tingling of the hands and feet)
Subacute combined degeneration (SCD) of the spinal cord and brain white matter
Other less common diseases
The bottom line
Vitamin B12 deficiency can happen in people who don’t get enough B12 in their diet or can’t absorb it well. Serious side effects can result. In severe cases, the damage is permanent. If you know the symptoms and risk factors for B12 deficiency, though, it’s a condition that can be easily treated and managed.
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References
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