4 Vitamin B12 Deficiency Symptoms You Need to Know

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 is not made by plants, either. It’s found in animal products, in foods where B12 has been added, or in supplement form. 

Teens and adults need about 2.4 mcg of vitamin B12 every day. Pregnant people need around 2.6 mcg, and those who are breastfeeding need 2.8 mcg of vitamin B12 per day. Infants and children need 0.4 mcg to 1.8 mcg, depending on their age.

EXPERT PICKS: WHAT TO READ NEXT

• Where can you get it? B12 can be found in everyday animal-based foods — like beef, seafood, poultry, and dairy.

• Do you need a B12 supplement? If your vitamin B12 levels are consistently low, a healthcare professional may recommend a prescription supplement to raise your levels to a normal range.

• How much per day? Find out how much vitamin B12 you really need, and what happens if you take too much.

Common symptoms of vitamin B12 deficiency

Not having enough vitamin B12 can cause complications in multiple body systems. That’s because vitamin B12 is needed for making certain cells, proper cell function, and repair. Having a vitamin B12 deficiency can affect how well your body makes new blood cells, nerve cells, and DNA.

Let’s take a closer look at four 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

• Headaches

• Feeling dizzy or like you might faint

• Fast or irregular heartbeat

Some people with B12 deficiency also have mouth sores or a swollen, painful tongue.

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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

• Memory loss

• 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 is also why low vitamin B12 is thought to play a role in heart disease, stroke, and dementia.

When should I contact my healthcare provider about vitamin B12 deficiency symptoms?

If you notice any physical symptoms of vitamin B12 deficiency, you’ll need to let your healthcare provider know right away. They will 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. 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.

The amount of vitamin B12 can be found on the nutrition label of foods where it has been added and doesn’t occur naturally. 

Not absorbing enough

Some people consume enough vitamin B12, but their body can’t absorb it. 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

How is B12 deficiency diagnosed?

A healthcare provider may do blood tests if you are 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.

A blood test will look for anemia and the size of your blood cells. Your provider will also check your vitamin B12 levels. More specialized tests may be done for advanced disease or if autoimmune disease is suspected.

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.

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. There is also a nasal spray, but it’s not absorbed as well as the injectable form. 

If medications or alcohol are interfering with absorption, these should 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:

• Nausea

• Diarrhea

• Rash

• Cough and congestion

Why trust our experts?

Written by:

Anne Jacobson, MD, MPH

Anne Jacobson, MD, MPH has been a board-certified family physician since 1999. She worked as a full-scope family physician (inpatient, outpatient, obstetrics, and office procedures) in the Cook County Ambulatory Health Network for 15 years.

Edited by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

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