Vitamin B12: Overview, Benefits, and Food Sources

What is vitamin B12?

Vitamin B12, also known as cobalamin, is one of the eight B vitamins that are essential for your body to work properly. These are also known as B-complex vitamins, and include:

• Thiamine (B1)

• Riboflavin (B2)

• Niacin (B3)

• Pantothenic acid (B5)

• Pyridoxine (B6)

• Biotin (B7)

• Folate (B9)

• Cobalamin (B12)

Your body cannot make vitamin B12, so you need to consume it in your food in order to meet your daily needs.

There are two forms of vitamin B12 that are active in the body: methylcobalamin and 5-deoxyadenosylcobalamin. Vitamin B12 supplements often contain cyanocobalamin or hydroxocobalamin, which are converted into the active forms of vitamin B12 in the body after you take them.

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• 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.

What are Vitamin B12’s benefits for your body?

As mentioned, vitamin B12 is an essential vitamin. This means your body cannot function properly without it. But your body can’t make vitamin B12, so the only way to get it is from food or supplements. 

Vitamin B12 has three major functions. It helps:

1. Support the bone marrow’s production of red blood cells

2. Protect your nerves

3. Make DNA (the genetic material in your cells)

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Your body also needs vitamin B12 in order to make certain hormones, proteins, and fats. And vitamin B12 plays a key role in your metabolism and energy levels, too.

Good to know: When we talk about vitamin B12 benefits, we’re referring to the role it plays in the day-to-day functioning of your body at the recommended daily levels. There isn’t an added benefit in taking more vitamin B12 than you need — more on that later. 

How much Vitamin B12 do you need?

People ages 14 years and older need 2.4 mcg of vitamin B12 every day. In most cases, you’ll get enough vitamin B12 from your diet if you consume animal products.

If your vitamin B12 levels are low or you do not eat animal products, you’ll likely need to take a vitamin B12 supplement. You can get it over-the-counter (OTC) as well as by prescription. Your healthcare provider will tell you the right vitamin B12 dosage to take for your needs.

What foods and supplements contain vitamin B12?

Vitamin B12 is naturally found in animal-based foods. These include:

• Beef: Beef liver is the richest source of vitamin B12, but other beef products (such as ground beef) also contain a good amount.

• Seafood: Salmon, tuna, and clams are among the best sources of vitamin B12 in seafood.

• Poultry: Chicken, turkey, and eggs also contain vitamin B12, though less than the beef and seafood options listed above.

• Dairy products: Milk, yogurt, and cheese all contain vitamin B12.

Vitamin B12 isn’t naturally found in plants. But some plant-based foods have added vitamin B12. These are referred to as fortified foods. Fortified foods can help you get enough vitamin B12 if you don’t eat animal-based foods regularly. You’ll see vitamin B12 listed in the nutrition facts of these foods to help you know how much is in each serving. Examples of fortified foods include:

• Nutritional yeast

• Some breakfast cereals

• Plant-based milks, such as almond, coconut, and soy

Vitamin B12 is also available in manufactured forms, such as: 

• Vitamin B12 supplements  

• Vitamin B-complex supplements

• Multivitamins

• Prescription medications, such as injectable cyanocobalamin or Nascobal nasal spray

Good to know: There’s one plant that contains moderate levels of vitamin B12. It’s a form of seaweed known as nori that’s often used in sushi. If you don’t consume animal products and aren’t interested in manufactured forms of B12, making nori a regular part of your diet may help you meet your vitamin B12 needs.

What are the symptoms of low vitamin B12 levels?

Common symptoms associated with a vitamin B12 deficiency include:

• Fatigue, palpitations, and pale skin: Vitamin B12 deficiency leads to a specific type of anemia that lowers your red blood cell count and causes these symptoms.

• Peripheral neuropathy: Vitamin B12 helps protect your nerves. So low levels over time can lead to nerve damage and neuropathy (numbness and decreased sensation in the hands and feet).

• Mood symptoms or cognitive impairment: Low vitamin B12 may contribute to depression or other changes in your mood. In severe cases, dementia-like symptoms or even psychosis may occur.

• Birth defects: Low vitamin B12 levels during pregnancy can lead to problems with the development of the brain and spinal cord in the growing fetus.

If you’re experiencing symptoms related to low vitamin B12, talk to your healthcare provider about testing your levels. They can determine if your levels are where they should be.

Do you need a vitamin B12 supplement?

Certain people are at a higher risk for low vitamin B12 levels. And certain health conditions can prevent you from absorbing vitamin B12 from your food. You may need a vitamin B12 supplement if you: 

• Have pernicious anemia (an autoimmune condition where your body doesn’t make a protein that’s needed to absorb vitamin B12))

• Have a health condition that affects your intestines, such as Crohn’s disease or celiac disease

• Have had intestinal surgery, such as a bowel resection or gastric bypass 

• Are vegetarian or vegan

• Are pregnant

• Take medications that lower vitamin B12 absorption (more on this later)

• Consume large amounts of alcohol regularly

• Are an older adult, as vitamin B12 absorption may decrease with age

Despite speculation, if your vitamin B12 levels aren’t low, taking B12 supplements hasn’t been definitively proven to:

• Reduce the risk of cardiovascular disease and stroke

• Improve cognitive function (thinking and memory) or prevent dementia 

• Treat autism spectrum disorder (ASD)

• Increase energy levels

Good to know: If you have a health condition or medical procedure that prevents your body from absorbing vitamin B12 from your food, an oral supplement isn’t likely to work for you. You’ll either need OTC vitamin B12 drops you can place under your tongue or a prescription form of vitamin B12 that’s injected or sprayed into your nose. 

What medications can affect vitamin B12 levels?

Some medications can prevent your body from absorbing vitamin B12 in food and oral supplements. If you’re taking any of these medications long-term, your healthcare provider may want to monitor your vitamin B12 levels.

Examples of these medications that may lower your vitamin B12 levels include:

• Proton pump inhibitors (PPIs), such as omeprazole (Prilosec)

• Histamine-2 receptor antagonists (H2 blockers), such as famotidine (Pepcid)

• Metformin (Glucophage, Glumetza)

• Anti-seizure medications, such as pregabalin (Lyrica) and topiramate (Topamax)

Be sure to provide your healthcare provider with an updated medication list so they can check for anything that may affect your vitamin B12 levels. Be sure to include any OTC medications or supplements you’re taking.

Is it safe to take vitamin B12 supplements every day?

If your healthcare provider tells you to take vitamin B12, taking it every day (or as your provider instructs) is the best way to keep your levels where they should be.

If you take more vitamin B12 than you need, your body gets rid of it in your urine. So if your vitamin B12 levels are normal and there’s no medical reason to take a vitamin B12 supplement, the money you’re spending is literally going down the drain.

There are a few other risks to know about taking vitamin B12 that are specific to certain health conditions. If you have kidney disease, megaloblastic anemia, or rare genetic conditions, large doses of injectable vitamin B12 may cause dangerous side effects. These health conditions are rare, and your provider will likely screen for them before prescribing you vitamin B12. But it’s a good idea to talk to your provider first before taking OTC vitamin B12 to make sure it’s safe.

FAQs

Disclaimer: The FDA does not test supplements for safety and effectiveness. Supplements can contain harmful substances. They can also affect how your medications work. Always speak with your healthcare provider before taking any supplement.

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Written by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Christina Palmer, MD

Christina Palmer, MD, is a board-certified family physician with a special interest in chronic care management, women’s health, mental health, and preventive care. She has over 10 years of experience in primary care research, innovation, and practice.

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