Vitamin B12 is an important nutrient that helps your nervous system work properly.
Your body can’t make vitamin B12 on its own, so you get it from food, drinks, or supplements. The nutrient occurs naturally in meat, fish, and dairy products and can be created in a laboratory.
Some people lack a protein that helps the body absorb vitamin B12 from foods and supplements. A lack of B12 (called a deficiency) can put you at higher risk for a specific type of anemia that makes you feel weak and tired.
What Does Vitamin B12 Do?
Vitamin B12, also called cobalamin, helps your body make DNA, nourishes your brain and nervous system, and helps maintain healthy red blood cells. It also helps your body convert food into energy.
When you eat foods that contain vitamin B12, hydrochloric acid in your stomach separates the vitamin B12 from the protein it was bound to in the food. Next, it combines with a protein called intrinsic factor, which your stomach makes, and then your body absorbs the vitamin B12.
You may be more likely to have low levels of vitamin B12 if you:
- Have certain conditions that make it difficult for your body to absorb vitamin B12, including some digestive problems
- Are a vegan or vegetarian and don’t eat many animal-based foods
- Are over age 50
- Have some types of anemia
Low levels of vitamin B12 can cause fatigue, weakness, memory loss, and other problems with your nervous system.
Vitamin B12 can help improve your health in some ways and protect against some health problems.
Vitamin B12 Benefits
Vitamin B12 can help you in different ways.
For many diseases and conditions, vitamin B12 has been considered a treatment. It can be used for fatigue, Alzheimer's disease, heart disease, certain types of cancer, high cholesterol, and sickle cell disease. However, the results have been mixed.
Here are some of the ways vitamin B12 may help improve your health or guard against problems.
May boost energy
If you have a vitamin B12 deficiency, you may feel tired and weak. Taking vitamin B12 can improve your energy if your body isn’t getting enough of the nutrient.
Vitamin B12 is sometimes referred to as an energy and athletic performance booster. But if you don’t have a deficiency, vitamin B12 doesn’t appear to increase energy or performance, studies have shown.
May help treat depression
Vitamin B12 plays a role in serotonin production, so a deficiency may be linked to depression. But research on the effects of vitamin B12 on depression has had mixed results. Some studies have found no clear evidence that vitamin B12 treats depression, but lower levels of vitamin B12 are linked to a higher risk of depression.
For people with major depressive disorder, a more severe form of depression, one study found that vitamin B12 supplements, along with antidepressants, greatly improved symptoms.
May protect from macular degeneration
Age-related macular degeneration is an eye disease that can cause blindness in older adults. Vitamin B12 supplements are believed to lower homocysteine, an amino acid in your bloodstream, which may help prevent macular degeneration.
One study found that a higher intake of B vitamins, including vitamin B12, was linked to a lower rate of age-related macular degeneration. In another study of 5,000 women aged 40 or older, those who took supplements of vitamins B12, B6, and folic acid had 34% fewer cases of macular degeneration after seven years than a placebo group.
May reduce the risk of birth defects
Vitamin B12 deficiency is common during pregnancy, and it’s tied to pregnancy complications. “Vitamin B12 may be needed if you’re pregnant or lactating,” especially if you’re also eating a plant-based diet, says Sue-Ellen Anderson-Haynes, MS, RDN, CDCES, owner of 360Girls&Women and spokesperson of the Academy of Nutrition and Dietetics.
For people with a vitamin B12 deficiency in the early stages of pregnancy, the child is at an increased risk of neural tube birth defects (birth defects that affect your baby’s brain, spine, or spinal cord) and low birth weight. Mothers with low B12 levels are also more likely to miscarry or give birth prematurely (early).
If you have low vitamin B12, you’re three times more likely to have a child with birth defects.
However, some research has found that high levels of vitamin B12 during early pregnancy are linked to childhood autism. This suggests that extra amounts of B12 can be harmful.
For pregnant people, the American College of Obstetricians and Gynecologists recommends 2.6 micrograms per day of vitamin B12. Because vitamin B12 may have both positive and negative effects if you’re pregnant, talk to your doctor or health care provider before taking a supplement.
May improve brain health
Vitamin B12 deficiency is tied to cognitive impairment (memory and thinking problems). One study found that low B12 levels, even within the lower normal range, can in part lead to poor memory performance.
Vitamin B12 is an important nutrient for the neurons in your brain. Brain atrophy, which refers to the loss of neurons in your brain, is connected to memory loss and dementia.
In one study, older adults with early-stage dementia who took vitamin B12 supplements to lower their blood homocysteine levels showed a slower rate of cognitive and clinical decline. This means that their symptoms worsened at a slower rate with the supplement.
However, research on vitamin B12 and cognitive function has had mixed results. A review found that for people without advanced neurological disorders, vitamin B12 supplements are unlikely to improve brain function.
More studies are needed to figure out how B12 supplementation affects cognitive function and neurodegenerative diseases.
May improve bone health
Some studies have found that vitamin B12 may help improve bone health. One study found higher B12 levels led to a slight decrease in bone fracture risk.
But some studies on vitamin B12 and bone health have shown mixed results. One review found that most studies didn’t show a strong link between vitamin B12 and bone mineral density. However, most of these studies were done on White people.
Some researchers have noted that ethnicity may be a factor in how people take up nutrients such as vitamin B12. This is because diets vary from one culture to another. Researchers have called for more studies on certain populations, including Asian people or postmenopausal and older women.
May increase RBC
Your body needs vitamin B12 to make red blood cells (RBCs), which carry oxygen throughout your body. Without enough oxygen, your body can’t function as well as it should.
A lack of B12 can cause a condition called vitamin B12 deficiency anemia. To treat it, your doctor may suggest vitamin B12 supplements or changes to your diet to increase the amount of B12 you get from food.
Sources of Vitamin B12
You can get vitamin B12 from animal foods such as meat and dairy. Plant foods typically don’t contain vitamin B12 unless they are fortified with it, such as some fortified cereals.
Vitamin B12 foods
Here are some good sources of vitamin B12 from food and drinks:
- Fish and shellfish
- Lean red meat and chicken
- Cheese and milk
- Eggs
- Yogurt
- Fortified cereals
- Fortified nutritional yeast
- Fortified vegan milk substitutes
Some specific examples of foods rich in vitamin B12 are beef liver, clams, and oysters (cooked).
Certain plant foods contain vitamin B12 as well, including nori (a type of dried seaweed) and dried shiitake mushrooms. But you would need to eat a lot of those to get significant amounts of vitamin B12.
To find out whether a food or drink has been fortified with vitamin B12, check the Nutrition Facts label.
Generally, it's best to get vitamins from whole foods. But doctors often suggest fortified foods to people over the age of 50. As we age, it's harder for our bodies to absorb vitamin B12 from food.
Aside from foods, you can also get vitamin B12 through different types of supplements.
A health care provider can help you figure out how much vitamin B12 you’re getting from the foods you’re eating. “As a dietitian, I would always review what they're currently eating and see what they may need, like a flexitarian may eat eggs every now and then. They may have chicken or fish, and they may not necessarily need B12 in addition to that,” says Anderson-Haynes. She also sugests getting lab tests done.
Vitamin B12 supplements
Vitamin B12 supplements come in several different types. Some supplements are vitamin B12 only, some are called B-complex supplements that contain B12, and some are multivitamin/mineral supplements that also contain B12.
Another type is called sublingual vitamin B12, which means it’s dissolved under your tongue. A prescription form of vitamin B12 also comes in a nasal gel that you spray into your nose.
With supplements, the amount of vitamin B12 in each dose can be different. It may also be well above the recommended amount, but these doses are generally considered safe, as your body absorbs only some of the B12. It’s always a good idea to check with your doctor before taking a supplement.
The best vitamin B12 supplement for you will depend on your health conditions and your B12 levels, among other factors.
If you’re choosing a supplement, “Look for a supplement that has the NSF stamp on it, because it's ensured that it's gone through testing, it's safe, and it's sanitary,” or look for the GMP certification, says Anderson-Haynes.
Vitamin B12 shots
Another type of vitamin B12 supplement includes shots. They’re usually a prescription form of vitamin B12 that’s used to treat vitamin B12 deficiency.
Your doctor may use injections if you have a severe B12 deficiency because you don’t have enough of a protein called intrinsic factor. If you don’t have enough of this protein, that means you have pernicious anemia.
Usually, you get vitamin B12 shots at a health care provider’s office or clinic, but sometimes, your provider may teach you how to inject yourself. If you do it yourself, follow their instructions carefully.
Vitamin B12 Dosage
The recommended dietary allowance (RDA) for vitamin B12 includes the B12 you get from food and any supplements you take. Here’s the RDA for people of different ages.
Category | Vitamin B12: Recommended Dietary Allowance (RDA) in micrograms (mcg) For children under age 1, only an adequate intake (AI) is available |
|---|---|
0-6 months | 0.4 micrograms/day |
7-12 months | 0.5 mcg/day |
1-3 years | 0.9 mcg/day |
4-8 years | 1.2 mcg/day |
9-13 years | 1.8 mcg/day |
14-18 years | 2.4 mcg/day |
Adults | 2.4 mcg/day |
Pregnant people | 2.6 mcg/day |
Breastfeeding people | 2.8 mcg/day |
Some supplements contain much more vitamin B12 than the RDA. But even at high doses, vitamin B12 is usually safe. This is because your body will absorb only as much as it needs, and the rest will pass through your pee. No tolerable upper intake level (UL) has been set for vitamin B12, meaning there’s no known limit for how much vitamin B12 you can safely take.
However, some research suggests that a very high intake of vitamin B12 may increase the risk of death. Experts also think that a high intake of B12 and B6 may raise the risk of hip fracture.
Is It Safe to Take Vitamin B12?
Vitamin B12 is typically safe. However, very high doses might cause side effects, such as:
- Headache
- Fatigue or weakness
- Nausea, vomiting, or diarrhea
- Tingling in your hands and feet
If you’re choosing a B12 supplement, the package may display the amount of vitamin B12 (in micrograms) as well as the percent daily value. If you take one that contains levels of vitamin B12 that are well above the RDA, you may have side effects such as gastrointestinal discomfort, says Anderson-Haynes.
“That's why it's really good for you to seek out a provider before you just go grab a supplement. Because you may be taking too much of something and may be having discomfort and not know why,” she says.
B12 supplements can interact with certain medicines, including:
- Chloramphenicol (Chloromycetin Sodium Succinate)
- Proton pump inhibitors
- Metformin (Glucophage, Glumetza, Riomet)
- Gastric acid inhibitors
If you’re taking any of these medications, talk to your doctor or pharmacist before starting a B12 supplement.
Because some research has found that very high doses of vitamin B12 may increase the risk of death, it’s a good idea to talk to your health care provider about the right dosage.
Takeaways
Vitamin B12 is an important nutrient that keeps your nervous system working properly. It’s important for your brain, red blood cells, and DNA. If you don’t eat animal products or if you have certain health conditions, you may be more likely to have a vitamin B12 deficiency. Your body doesn’t make vitamin B12 on its own, so you need to get it from food or supplements.
Vitamin B12 FAQs
How can I increase my B12 naturally?
You can increase your intake of vitamin B12 naturally by eating animal-based foods rich in vitamin B12, such as fish, meat, and dairy.
Can vitamin B12 deficiency be a sign of cancer?
Some research suggests vitamin B12 deficiency is linked to an increased risk of cancer, but more studies are needed.
Is B12 safe to take daily?
Yes, vitamin B12 is generally considered safe to take daily. But if you’re taking a supplement, it’s a good idea to check with your health care provider about the right dosage.
Can lack of B12 cause fatigue?
Yes. If you have a vitamin B12 deficiency, that can cause fatigue.
Does vitamin B12 help with memory loss?
It might. Memory loss is a symptom of vitamin B12 deficiency. If you have a deficiency, eating foods rich in vitamin B12 or taking supplements may help ease this and other symptoms.
