Vitamin B12 is one of those nutrients most people do not think about until something goes wrong. It helps make red blood cells, keeps nerves healthy and supports DNA production. You get it naturally from animal foods like meat, fish, eggs and dairy. For most of life, that is enough. But after about 50, many people quietly start absorbing less of it, and low B12 can creep up over years before anyone notices.
Why absorption drops with age
To absorb B12 from food, your stomach needs acid to separate it from the protein it is bound to. Then it needs a substance called intrinsic factor to carry it into the body. As we get older, many people develop a condition called atrophic gastritis, which reduces stomach acid. The NIH estimates it affects a significant share of older adults.
Here is the interesting part: the B12 in supplements and fortified foods is not bound to protein, so it does not need stomach acid to be released. That is why the NIH Office of Dietary Supplements advises that adults over 50 get most of their B12 from fortified foods or supplements.
Who else is at higher risk?
- People taking metformin, a common diabetes medicine, for a long time.
- People taking acid reducers such as proton pump inhibitors or H2 blockers for a long time. See do antacids affect your bones and kidneys?.
- Vegans and some vegetarians, because B12 is found naturally only in animal foods.
- People who have had weight loss surgery or parts of the stomach or intestine removed.
- People with pernicious anemia, an autoimmune condition that blocks intrinsic factor.
- People with digestive conditions such as Crohn's disease or celiac disease.
Signs that B12 may be low
Low B12 can develop slowly, and the signs are easy to blame on other things:
- Tiredness and weakness.
- Pale skin.
- Numbness or tingling in the hands and feet.
- Trouble with balance.
- A sore, red tongue.
- Memory problems, confusion or low mood.
Some nerve damage from long-term B12 deficiency can become permanent, which is why catching it early matters. A blood test can check your level. Your doctor may also test related markers if the result is borderline. See supplements and lab tests.
How much do you need?
The recommended amount for adults is 2.4 micrograms a day. That sounds tiny, and it is. But because absorption from high-dose supplements is limited, products often contain much more, such as 100 to 1,000 micrograms. That is why you see B12 listed at thousands of percent of the Daily Value. There is no established upper limit for B12 because it has low potential for harm. See what % Daily Value means.
Which form is best?
You will see two main forms:
- Cyanocobalamin is the most common, inexpensive and well studied form.
- Methylcobalamin is often marketed as more natural or better absorbed.
Both work for most people. Do not pay a large premium for methylcobalamin unless your doctor has a specific reason to recommend it. People with pernicious anemia or severe absorption problems may need B12 injections or high-dose oral B12 under medical supervision.
Food sources
- Clams and liver are extremely rich in B12.
- Fish such as salmon, trout and tuna.
- Beef, chicken and eggs.
- Milk, yogurt and cheese.
- Fortified breakfast cereals and nutritional yeast, which are especially useful for vegans.
A simple plan if you are over 50
- Ask your doctor whether a B12 test makes sense, especially if you take metformin or acid reducers.
- Include fortified foods or take a supplement or a multivitamin that contains B12.
- If you are low, follow your doctor's plan for dose and retesting.
The bottom line
B12 absorption from food often declines after 50, and certain medicines and diets add to the risk. Fortified foods and supplements are well absorbed even when stomach acid is low. A simple blood test and a low-cost supplement can prevent a deficiency that is easy to miss and important to catch. See our vitamin B12 page for more detail.