Vitamin B-12: Deficiency, Function, Source, Risk, And More


Vitamin B-12 is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement and a prescription medication.

It is also known as cobalamin and plays an important role in your body’s health.

B-12 helps prevent anemia and contributes to the production of DNA and RNA, maintaining a healthy nervous system, as well as regulating blood glucose levels.

Because this vitamin has such far-reaching effects on your body, it can be extremely dangerous to have too little B-12 in your system.

Vitamin B-12 deficiency symptoms include – shortness of breath, weakness, and fatigue, among other things.

What does vitamin B-12 do in your body?

Most notably, it plays a role in brain health as well as a nervous system function (1).

In addition to its neuroprotective properties, vitamin B-12 is also known for aiding energy metabolism and healthy heart function.

Though most people should be able to easily get their recommended daily intake of vitamin B-12 from food sources alone.

Vitamin B12 is needed to form red blood cells and DNA, which is also a key player in the function and development of brain and nerve cells (2)

A nutrient found in meat, fish, and other foods, vitamin B-12 is important for a number of essential body functions (3)

Why you need it (and how much)

As we know that it’s an essential nutrient—meaning it’s not stored in your body, so you need a reliable source of it every day.

While vitamin B-12 deficiency symptoms may sound scary (and they are), know that many people don’t realize they have a deficiency over time, it can cause irreversible damage.

NOTE: The recommended daily upper limit of B12 for adults is just 2.4 micrograms (mcg).

And steer clear of long-term side effects like numbness or tingling in your hands and feet or shortness of breath, keep eye on common symptoms of vitamin b-12 deficiency.

The signs of vitamin B-12 deficiency

Your body requires vitamin B-12 for cellular and neurological functions because it’s difficult for your body to store vitamin B-12, any deficiency must be addressed quickly (4).

Symptoms of a deficiency include:

  • Fatigue
  • numbness or tingling in your hands and feet
  • weakness
  • weight loss (or failure to gain weight)
  • paleness
  • dizziness
  • shortness of breath

For proper absorption into your bloodstream, you need intrinsic factor (IF).

If you’re deficient in IF or have pernicious anemia where red blood cells decreased caused by chronic inflammation of the stomach lining, that leads to diarrhea, heartburn, or bloating after eating protein.

Certain medical conditions and lack of certain nutrients can cause symptoms of deficiency that should be treated by your doctor with supplementation or dietary changes.

Sources of vitamin B-12

For non-vegetariansEggs, animal liver, kidneys, beef, and fish like salmon, Trout, meat, and fortified are excellent sources of vitamin B-12 (5).

If you are vegetarian – soybeans, dairy products, quinoa, leafy greens (like spinach), tempeh, and nutritional yeast are one of the excellent sources of vitamin B-12 (6).

And while it’s not always an option, supplementing with vitamin B-12 is also an easy way to make sure you get enough in your diet (7).

The most common form of vitamin B12 in dietary supplements is cyanocobalamin and other forms of vitamin B12 in supplements are adenosylcobalamin, methylcobalamin, and hydroxocobalamin (8).

NOTE: A study showed that 50.15 of vegans and 38.7% of vegetarians used at least one supplement as a source of vitamin-12 (9).

In addition, vitamin-B12 supplements and fortified foods, animal-source foods are still important as vitamin B-12 sources, particularly among non-vegetarians (10).

Benefits of B12

There are multiple health benefits of vitamin B and folic acid these include:

Folic acid and other B vitamins are low-cost ways of reducing plasma homocysteine levels and might be a way to lower cardiovascular risk (11).

Studies have shown that vitamin B12 and other vitamin B reduce insulin resistance in patients with metabolic syndrome and markers for oxidative stress and inflammation (12) (13).

Slattery et al reported suggest that a high intake of folate, vitamin B6, and B12 were allied with reducing the risk of colon cancer by about 30 to 40% (14).

Also, pregnant women also require a sufficient amount of B12 level for the fetus’s brain and nervous system.

Studies have shown that low vitamin b12 is allied with poor bone health, like osteoporosis, especially in women, so make sure to consume recommended amount, especially after menopause (15) (16).

Check OUt – Ways To Maintain Your Bone Health – According To Research

For mental health

Some studies have shown that folic acid might be more vital than vitamin B12 in cognitive function, and also improve the symptoms of delirium (17) (18).

Few studies or insufficient data show that B12 improves the cognitive function of people with dementia (19).

In older adults

Vitamin B12 absorption is a highly unique process that often becomes less efficient with age and involves the stomach, pancreas, and small intestine (20).

Its deficiency rises with age, but only about 10% of those with low vitamin B12 also have low folate levels (21).

Risk (Too much and Too low)

Taking too much – In some people, taking too much vitamin B-12 may cause – headaches, depression, fatigue, and insomnia.

These symptoms usually go away on their own when you stop taking high doses of vitamin B-12.

People who take a lot of vitamin B-12 are also at risk for developing cobalt and vitamin B-6 deficiencies.

  • Cobalt is important for making red blood cells (RBC)
  • Vitamin B-6 helps break down proteins in your body

Taking too low – Since B12 has a very low level of toxicity, taking more than recommended daily, can cause adverse side effects for most people.

NOTE: Pregnant and lactating women following vegetarian or vegan diets are more at risk of deficiency due to the increased metabolic demand for vitamin B-12 (22).

Some studies suggest that high levels of vitamin B-12 are associated with mortality (23) (24) and some other studies do not suggest any link (25) (26).

A study showed a relationship between high B12 and mortality after adjusting for liver function and liver disease (27).

Possible side effects of taking supplements

Due to their high dosage, it’s possible that you will experience side effects from supplements these include:

In addition, Metformin, commonly used in the treatment of type II diabetes, may decrease vitamin B12 levels.

Which can be alleviated by taking a break from taking supplements for a few days.

NOTE: Talk to your doctor, If you notice any severe reactions, it may also interact with other medicines, so make sure immediately stop using your supplements.

Pregnancy and Vitamin B-12

Many studies suggest that Vitamin B-12 concentrations during pregnancy are closely allied with fetal (28) (29) and early infant (30).

During a randomized trial, it is shown that was a high prevalence of vitamin B12 deficiency in Indian women during pregnancy around 40-70% (31).

During pregnancy B12 deficiency can affect both mother and infants.

Vitamin B-12 deficiency also leads to common pregnancy complications such as – small for gestational age, low birth weight, intrauterine growth restriction, and recurrent pregnancy loss (32) (33) (34) (35).

Infants born with a vitamin-B12 deficiency can impair infant growth, anemia, psychomotor function, and brain development, which may be irreversible (36) (37).

NOTE: So make sure to consume a sufficient amount of B12 (a pregnant lady should consume 2.6 mcg per/day and 2.8 if women in breastfeeding).

How long before it kicks in?

It can take a couple of months for symptoms of deficiency, like numbness or weakness in your hands and feet, memory loss, and cognitive difficulties.

If you experience any of these symptoms, talk to your doctor and run a vitamin panel, it may be time for some extra supplementation.

And if you are on any medication that inhibits B12 absorption (like metformin, colchicine), so talk to your doctor before taking any supplement, whether it is herbal.


It is also known as cobalamin and plays an important role in your body’s health including needed for red blood cells and DNA, and brain and nerve cell development.

Vitamin B-12 deficiency is most all around the world common symptoms like fatigue, weakness, weight loss, paleness, dizziness, shortness of breath, and numbness in your hands and feet.


Hello, I'm Sahil bisht, I am a Mechanical engineer, As well as, aspiring blogger with an obsession for health. This blog delicate to people who want to learn in health.

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