What Does Vitamin B12 Do? All You Need to Know

what does vitamin b12 do

That’s an important question because it can be hard to tell. Let’s start with

Why Do We Need Vitamin B12?

Vitamin B12 is also known as cobalamin, because it contains the trace element cobalt.  B12 is a water-soluble vitamin. If you eat enough cobalaminand if your body can use it properly, you make millions of nice, round, healthy red blood cells every day. If you don’t eat enough, or you can’t use it properly, you can’t make enough red blood cells, and the ones you do make are too large and fragile to work well.

Here is why cobalamin is important for us:

  • For the formation of healthy red blood cells
  • Plays a key role in the normal functioning of the brain and the nervous system
  • To make the outer coverings of your nerves
  • For a healthy immune system
  • It is involved in the metabolism of every cell of the human body, affecting DNA synthesis and regulation.
  • When you don’t have enough red blood cells to carry, you develop anemia
  • All your cells, not just your red blood cells, need cobalamin to grow and divide properly. For example, you need it to make all the different cells in your immune system, including white blood cells

How Do We Get Our Natural Dose Of Vitamin B12

Cobalamin is mostly found only in animal foods such as liver, kidney, red meat, eggs, shellfish, fish, dairy products.

To get even the small amount of cobalamin your body needs to be really good at absorbing it. Fortunately, most people take in more than twice the Recommended Dietary Allowance(RDA) through their diet, so they usually get enough.

Although cobalamin is a water-soluble vitamin, you still store some of it in your liver and kidneys. Your body is really good at recycling cobalamin, so you don’t use up your body stores quickly.

As you get older, your ability to absorb cobalamin decreases. You may need supplements.

People who don’t eat animal foods and have a strict vegetarian diet may need cobalamin supplements.

Absorption Process Of Vitamin B12

Gastrointestinal absorption of vitamin B12 occurs in the small intestine by an active process requiring the presence of intrinsic factor.

Intrinsic factor is a glycoprotein, which the gastric parietal cells secrete after being stimulated by food.

A lack of intrinsic factor results in malabsorption of cobalamin. Vitamin B12 forms a complex with intrinsic factor (IF) in the stomach.

Generally speaking, people deficient in cobalamin are eating enough of it. The problem is that they’re not absorbing it because they don’t have enough intrinsic factor. Fortunately, today you can take your cobalamin supplements as tablets or capsules.

Causes Of B12 Deficiency

Lack Of Intrinsic Factor

You lack the intrinsic factor. Without Intrinsic factor, absorption is not possible and a severe and persistent deficiency develops that cannot be prevented by the usual dietary intakes of vitamin B12. You’ve had part of your stomach surgically removed. You might not be making enough intrinsic factor in what’s left of your stomach. Discuss supplements with your doctor.

Pernicious Anemia

You have Pernicious anemia (a hereditary autoimmune disease that chiefly affects persons post middle age). When the anemia comes from a shortage of cobalamin in the diet, it’s called megaloblastic anemiaWhen it comes from a lack of intrinsic factor, it’s called pernicious anemiaThe causes are different, but the result is the same, you don’t have enough red blood cells, and the ones you do have are too big and fragile to survive long in your circulation.

Vegetarian Diet

You’re a strict vegetarian. Because cobalamin is found naturally only in animal foods, people who don’t eat these foods can get deficient if they don’t take supplements. The risk of nutritional deficiency is increased in vegetarians. There have also been reports of vitamin B12 deficiency in infants breastfed by vegetarian mothers. Strict vegetarians should take a vitamin B12 supplement regularly.

Old Age

You’re over age 50. As you get older, you naturally make less intrinsic factor and absorb less cobalamin. Sometimes you stop making intrinsic factor completely. Clinical cobalamin deficiency due to dietary insufficiency is rare in younger people, but occurs more frequently in older people. Vitamin B12 deficiency affects 10-15% of individuals over the age of 60.


You’re pregnant or breastfeeding. Your growing baby is taking a lot of your cobalamin. You need to get extra cobalamin in your food or through supplements.


You smoke cigarettes. Smokers have low blood levels of cobalamin and all the other B vitamins.

Acid Suppressing Drugs

You regularly take Acid-Suppressing drugs like PPIs (omeprazole, esomeprazole, rabeprazole, lansoprazole etc) to treat acid reflux, heartburn or ulcers. The long-term use of these drugs that affect gastric acid production interferes with your absorption of cobalamin. Talk to your doctor about supplements.

Potassium Supplements

You’ve been taking prescription potassium supplements for a long time. These drugs can interfere with your absorption of cobalamin. Talk to your doctor about supplements.


You are an alcoholic. In alcoholics, vitamin B12 intake and absorption is reduced, while the elimination of this vitamin increases.

Symptoms Of Having A Vitamin B12 Deficiency 

  • Paresthesia or tingling, pins and needles feeling, burning, numbness in hands and feet
  • Depression
  • Trouble sleeping
  • Memory loss
  • Male and female infertility
  • Anemia resulting from impaired red blood cell production
  • Peripheral Neuropathy
  • Pale Yellow Skin Color
  • Painful, red tongue
  • Mouth ulcers and canker sores
  • Constipation
  • Vision disturbances
  • Difficulty walking and balance problems
  • Perceptible differences in mood, thoughts, feelings and behavior
  • Confusion and difficulty thinking. In severe cases, dementia

The symptoms of vitamin B12 deficiency can develop slowly and worsen over time.

Treatment Of Vitamin B12 Deficiency

Your doctor would order a blood test to find out if you are B12 deficient.  Serum cobalamin remains the 1st line test.

If you are low on B12, then your doctor will go for further investigation to find the cause and will advise you the best treatment accordingly.

B12 supplements usually have anywhere from 100 to 500 mcg. Even 100 mcg is a lot more than the RDA, but it’s virtually impossible to overdose on cobalamin. Any excess is just excreted.

If you’re taking cobalamin because you don’t make enough intrinsic factor to absorb it from your food, will you be able to absorb it from a pill? Good question.

A lot of doctors would say no and make you come in for shots instead. In fact, if the supplement dose is big enough (500 to 1000 mcg), you will absorb enough from it, even if you don’t make any intrinsic factor at all. If you have pernicious or megaloblastic anemia, discuss oral cobalamin supplements with your doctor before you try them.

If your body is not able to absorb B12 from your diet, then you may have to take supplements or shots regularly for the rest of your life.

Consult your physician to find the best treatment option for you.


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