Vitamin B12 keeps your nerves and blood cells healthy and helps make DNA. Because it is found mainly in animal foods, vegetarians, vegans and older adults often ask whether they are getting enough. This guide explains B12 deficiency symptoms, daily needs, food sources, who is at risk and which medicines can affect B12, using the NIH Office of Dietary Supplements consumer fact sheet.
How Much Vitamin B12 Do You Need?
The NIH lists these recommended daily amounts:
- Children 1 to 3 years: 0.9 mcg
- Children 4 to 8 years: 1.2 mcg
- Children 9 to 13 years: 1.8 mcg
- Teens and adults: 2.4 mcg
- Pregnant teens and women: 2.6 mcg
- Breastfeeding teens and women: 2.8 mcg
Best Food Sources of Vitamin B12
Vitamin B12 occurs naturally in a wide variety of animal foods, and plant foods have none unless they are fortified.
- Clams, oysters and beef liver, some of the best sources
- Fish, meat and poultry
- Eggs, milk and other dairy products
- Fortified breakfast cereals and nutritional yeast
Symptoms of Vitamin B12 Deficiency
The NIH notes that deficiency symptoms can take several years to appear, because the body stores a large reserve of B12. Signs can include:
- Tiredness or weakness from megaloblastic anemia
- Pale skin, heart palpitations and loss of appetite
- Numbness or tingling in the hands and feet
- Problems with balance, depression, confusion and poor memory
- A sore mouth or tongue
In infants, deficiency can cause failure to thrive and delayed developmental milestones. These symptoms have many possible causes, so a blood test and a doctor visit are needed to confirm B12 deficiency.
Who Is at Risk of Low Vitamin B12?
- Older adults with low stomach acid. The NIH advises people over 50 to get most of their B12 from fortified foods or supplements.
- People with atrophic gastritis
- People with pernicious anemia, who cannot make the intrinsic factor needed to absorb B12
- People who have had some stomach or intestinal surgery
- People with celiac disease or Crohn disease
- Vegetarians and vegans, including pregnant or breastfeeding women who follow these diets and their babies
Medicines That Can Lower Vitamin B12
- Stomach acid reducers such as omeprazole, lansoprazole, cimetidine and ranitidine can interfere with absorbing B12 from food.
- Metformin, used for type 2 diabetes, might reduce B12 absorption and lower blood levels.
Do not stop any prescribed medicine on your own. If you take one of these long term, ask your doctor whether your B12 level should be checked.
Vitamin B12 Supplements and Safety
B12 supplements are usually sold as cyanocobalamin, and other forms include methylcobalamin, adenosylcobalamin and hydroxycobalamin. The NIH says research has not shown any one form to be better than the others. Doses of 500 mcg or 1,000 mcg are common, but the body absorbs only a small percentage of such large doses, and these doses are considered safe. Pernicious anemia and severe deficiency are usually treated with injections prescribed by a doctor.
When to See a Doctor
- You have ongoing tiredness, numbness or tingling, or memory problems
- You follow a vegan or vegetarian diet and do not use fortified foods or supplements
- You take metformin or acid-reducing medicines long term
- You have a digestive condition or have had stomach or bowel surgery
Helpful Video
Frequently Asked Questions
How much vitamin B12 do adults need per day?
Adults need 2.4 mcg a day, rising to 2.6 mcg during pregnancy and 2.8 mcg while breastfeeding, according to the NIH.
What foods are rich in vitamin B12?
Clams, oysters, beef liver, fish, meat, poultry, eggs and dairy are good sources. Fortified cereals and nutritional yeast help vegetarians and vegans.
What are the early signs of B12 deficiency?
Tiredness, weakness, pale skin, tingling in the hands and feet, poor balance, memory problems and a sore tongue. Symptoms can take years to appear.
Can vegetarians get enough vitamin B12?
Vegetarians who eat dairy and eggs can get some, but vegans need fortified foods or supplements because plant foods contain no natural B12.
Does metformin cause vitamin B12 deficiency?
Metformin might reduce B12 absorption and lower blood levels, so people who take it long term should ask their doctor about checking B12.
Related reading: Folic Acid and Folate guide | Iron Deficiency guide | Neurolab Injection (B-vitamin injection)
Sources
- NIH Office of Dietary Supplements: Vitamin B12 fact sheet for consumers
- NIH Office of Dietary Supplements: Folate fact sheet for consumers
Medical disclaimer: this article is for general information and does not replace advice from a qualified doctor. Do not start, stop or change any supplement or medicine without medical advice.