One of the eight B vitamins, vitamin B12 is essential to many bodily functions. It helps with the metabolism of every cell in the body and is necessary for the proper function of the nervous system.
This vital nutrient also aids in red blood cell production and prevents anemia. A deficiency in vitamin B12 can lead to a number of symptoms, so it’s important to make sure you’re getting enough!
Who is at risk for deficiency?
Vegans and vegetarians are at risk for vitamin B12 deficiency because the vitamin is found naturally in animal products. Older adults are also at risk because the body’s ability to absorb vitamin B12 decreases with age.
People with digestive disorders or who have had gastrointestinal surgery may also be deficient in vitamin B12.
Table of Contents:
- Vitamin B12 and Metabolism
- Vitamin B12 and the Nervous System
- Vitamin B12 and Anemia
- Vitamin B12 Deficiency Symptoms
- Who Is at Risk for Vitamin B12 Deficiency?
- Conclusion
Vitamin B12 and Metabolism
Vitamin B12 is an essential nutrient that helps the body convert carbohydrates into energy. It also plays a role in fat and protein metabolism.
Vitamin B12 deficiency can lead to fatigue, weight gain, and other health problems. Most people get enough vitamin B12 from their diet.
However, some people may be at risk for vitamin B12 deficiency, including vegans and vegetarians, older adults, and people with certain medical conditions.
Vitamin B12 supplements are available to help people get enough of this important nutrient.
Vitamin B12 and the Nervous System
A deficiency of vitamin B12 can lead to neurological problems, such as numbness and tingling in the hands and feet, depression, memory loss, and dementia.
While most people get enough vitamin B12 from their diet, some people may be at risk for deficiency due to certain medical conditions, such as pernicious anaemia, or due to medications that can interfere with absorption of the vitamin.
If you are concerned that you may be deficient in vitamin B12, talk to your doctor about getting a blood test to check your levels.
Treatment for vitamin B12 deficiency usually involves taking supplements or receiving injections of the vitamin.
Vitamin B12 and Anemia
Anemia is a blood condition in which there are not enough healthy red blood cells to carry oxygen throughout the body. This can cause fatigue, shortness of breath, and other symptoms. Vitamin B12 is essential for the production of red blood cells.
Without enough vitamin B12, your body can’t make enough healthy red blood cells, and you may develop anemia. If you think you may be at risk for anemia, talk to your doctor.
They can order a blood test to check your vitamin B12 levels. If your levels are low, they may recommend supplements or injections.
Eating a healthy diet is also important for preventing anemia. Make sure to include foods that are rich in iron, folate, and vitamin B12.
These nutrients are essential for the production of healthy red blood cells.
Vitamin B12 Deficiency Symptoms
A lack of vitamin B12 can lead to a number of health problems, including fatigue, weakness, constipation, loss of appetite, and weight loss.
Who Is at Risk for Vitamin B12 Deficiency?
A lack of vitamin B12 can lead to anemia, fatigue, and other health problems. People who follow a vegetarian or vegan diet are at risk for vitamin B12 deficiency because the vitamin is found mainly in animal products.
Those who have had weight-loss surgery or have certain gastrointestinal disorders may also be at risk, as they may not be able to absorb vitamin B12 properly.
Additionally, people who take certain medications (such as metformin and proton pump inhibitors) or have been exposed to stomach acid-reducing agents may also be at risk for vitamin B12 deficiency.
If you are concerned that you may be at risk for vitamin B12 deficiency, speak to your doctor. They can order a blood test to check your vitamin B12 levels and make recommendations on how to increase your intake of the vitamin if necessary.
Conclusion
From helping with metabolism and red blood cell production to preventing anemia, vitamin B12 is vital for good health.
If you think you may be deficient in vitamin B12, talk to your doctor about getting tested and starting supplementation.
B12 and Brain Health
Vitamin B12 plays a crucial role in maintaining cognitive function. Research has linked B12 deficiency to an increased risk of memory problems, cognitive decline, and even dementia in older adults. The vitamin helps maintain the myelin sheath — the protective coating around nerves — which is essential for fast, efficient nerve signaling throughout the brain.
Studies published in the American Journal of Clinical Nutrition have found that people with low B12 levels tend to score lower on cognitive tests and have more brain atrophy (shrinkage) over time. Maintaining adequate B12 levels throughout life may help protect against age-related cognitive decline.
B12 and Energy: Separating Fact from Hype
B12 is widely marketed as an "energy vitamin," but the reality is nuanced. B12 helps convert food into glucose, which your cells use for fuel. If you're deficient, supplementing B12 will genuinely boost your energy levels. However, if your B12 levels are already normal, taking extra B12 is unlikely to give you a noticeable energy surge — your body simply excretes the excess.
That said, many people are mildly deficient without knowing it. If you've been feeling sluggish despite getting enough sleep, it's worth having your B12 levels checked.
How Much B12 Do You Need?
The recommended daily intake varies by age and life stage:
- Adults (19+): 2.4 mcg/day
- Pregnant women: 2.6 mcg/day
- Breastfeeding women: 2.8 mcg/day
- Children (4–8): 1.2 mcg/day
Because B12 is water-soluble, there is no established upper limit for supplementation. Your body absorbs what it needs and eliminates the rest through urine. This makes B12 one of the safest vitamins to supplement, whether through food, pills, or newer delivery methods like B12 vapes.
Getting Tested for B12 Deficiency
A simple blood test can measure your B12 levels. Normal ranges are typically 200–900 pg/mL, though many experts consider levels below 400 pg/mL to be suboptimal. If you fall in the low-normal range and experience symptoms like fatigue or brain fog, your doctor may recommend supplementation even if you're not technically "deficient."