What are the normal levels of vitamin b12 in the body?

Knowing and maintaining normal levels of vitamin B12 at an exact point is essential for good health. B12 fulfills functions both physically and nervously, creating compounds of the organism and much more. Thus, it is necessary to have a suitable warehouse of this one so that these functions can be carried out.

Cobalamin is stored in the liver, where it has a life span of 2 to 3 years; during this period of time, the body is taking the amount it needs at any given time. Therefore, if we don’t take enough but we have reservations, we may not realize that we are suffering from a negative pathology until some time has passed.

Recommended daily allowance of vitamin B12

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To ensure normal levels of vitamin B12 it is very important to consider the recommended daily intake of this micronutrient. It basically depends on age and some other circumstances.

Recommended daily doses of Vitamin B12 according to EFSA


Quantity (mcg*)

Up to 6 months

0.4 mcg

From 7 to 12 months

0.5 mcg

From 1 to 3 years

0.9 mcg

From 4 to 8 years old

1.2 mcg

From 9 to 13 years old

1.8 mcg

14 to 18 years old

2.4 mcg


2.4 mcg

Pregnant women

2.6 mcg

Breastfeeding women

2.8 mcg

We must guarantee this daily contribution to the body to reach normal blood levels of cobalamin and not have any health problems. This is achieved, as we will see later, both with the consumption of foods rich in vitamin B12 and with the cyanocobalamin supplementation created in the laboratory, ideal for those people who do not consume food of animal origin, who have problems with absorption and synthesis of nutrients or who simply do not follow their diet and do not want to worry about it.

Main functions of B12 in the body

As we say, this vitamin has a leading role in many functions in the body, let’s see which are the most important.

  • It is responsible for the production of red blood cells, which will transport oxygen to the cells through the blood.
  • It also plays a very important role in bone marrow regeneration along with folic acid.
  • The improvement in the quantity and quality of neurotransmitters must also be highlighted.
  • Another of the most well-known functions is that it participates in the production of energy in the organism; that is why having a low level of this, the first symptoms are usually fatigue and weakness.

Another less known, but also very important, function of cobalamin is to improve the symptoms of mental illness such as depression. In neuropathies, too, optimal vitamin B12 levels contribute positively to minimizing nerve pain, as well as reducing numbness and tingling in the extremities.

What are the normal blood levels of vitamin B12?

Cobalamin vitamin B12 recommended daily dosage

Comparative table of blood vitamin B12 levels


Serum value pg/ml

Serum value pmol/l

High deficiency

150 pg/ml

110 pmol/l


200 pg/ml

150 pmol/l

Possible deficiency

200-300 pg/ml

150-220 pmol/l

Normal levels

300-900 pg/ml

220-665 pmol/l

Overall, the optimal value of cobalamin is considered between 200 and 500 pg/mL. Values below this figure indicate a B12 deficiency in the organism that may be mild, moderate or severe.

Similarly, too much B12 is also considered a pathology to be addressed.; values above 900 pg/mL require immediate medical attention for assessment and treatment.

When it comes to testing, whether specific to the level of B12 if you are suspicious or general, you need to know that there are a number of drugs that can affect test results.

These are:

  • Colchicina
  • Neomycin
  • Paraaminosalicic acid
  • Phenytoin

If we are prescribing any of the above drugs, it is necessary to inform the doctor so that he or she can determine whether and for how long to stop taking them.

Symptoms due to lack and too much B12 in blood

As we have pointed out, the lack of cobalamine is a disease that can become serious and has truly harmful consequences for health in the medium and long term. In some cases, the warning signs do not appear until many months later, while the body degenerates. Therefore, it is important to have regular medical tests.

Symptoms of low vitamin B12 levels usually include disorientation, paleness, lack of energy, numbness, and tingling in the legs and arms. In addition, if the situation persists, more serious pathologies such as dementia and even loss of brain mass may occur in advanced ages.

On the other hand, it should be noted that some cases of cancer are associated with patients with high vitamin levels, above 900 pmol/L.

The symptoms that alert of this pathology are the following:

  • Skin rashes with no apparent cause
  • Vomiting and nausea
  • Insomnia
  • Common headaches
  • Palpitations
  • Nervousness

High levels of vitamin b12 in the blood and possible related diseases

In some cases, high blood levels of B12 are due to serious illness. In the course of these diseases, the following mechanisms produce high B12 values:

  • Due to the excessive production of haptocorrines
  • Due to lack of excretion of vitamin B12
  • By releasing large amounts of B12 from the body’s reserves in the liver
  • When producing B12 analogues due to bacterial overgrowth

The following is a list of the most common diseases associated with very high blood levels of vitamin B12:

Liver tumors

Possible causes:

  • Failure to excrete B12
  • Increased production of transcobalamin

Other tumors

  • Breast cancer
  • Colon cancer
  • Gastrointestinal tumors
  • Pancreatic Cancer

Possible causes:

  • Increased production of transcobalamin

Blood diseases

  • Chronic myeloid leukemia Causes Increased production of granulocytic haptocorrins
  • Polycythemia vera Causes Increased release of granulocytic haptocorrins
  • Myelofibrosis (osteomyelofibrosis, OMF, fibrosis of the bone marrow) Causes Increased production of transcobalamin
  • Hypereosinophilic syndrome Causes Increased haptocorrine production
  • Acute leukemia Causes Increased haptocorrin production

Liver diseases



  • Release of vitamin B12 from the liver reservoir
  • Lack of production of transcobalamin II



  • Lack of absorption of vitamin B12 by the liver.

Alcoholic liver disease


  • Lack of production of transcobalamin II
  • Excessive production of transcobalamin I and II

Kidney Diseases

Kidney failure Causes Lack of vitamin B12 excretion and accumulation in the blood.

Intestinal diseases

Bacterial overgrowth of the intestine Causes Increased production of B12 analogues by bacteria

Vitamin b12 blood tests how to do them correctly?

Another very common cause of high blood levels is that the blood test was done immediately after an injection of vitamin B12. This should be avoided and a waiting period of 7 to 10 days should be maintained; otherwise, the results will be extremely falsified: vitamin B12 has not yet been metabolized and high blood levels are only one effect of injections. In these cases, high blood levels are absolutely harmless.

In addition, taking oral supplements in high doses can greatly increase blood levels; here too, the same case is observed. Therefore, if high blood levels are measured in the course of vitamin B12 supplementation, the first step is to recheck the blood level after 10 days without taking B12 preparations, to compare the results and have much more reliable data.

What if you have high levels of vitamin B12 in your blood?

High blood levels of vitamin B12 should always be studied to rule out serious illness. However, if high levels of B12 are detected in blood, there is no reason to panic at first; these are often simple measurement errors because the interval between intake of preparations and blood tests was not respected.

Which foods contain more vitamin B12 to reach optimum levels?

Foods of animal origin rich in vitamin B12

In order to guarantee normal blood levels of vitamin B12, it is essential to follow a rich and varied diet, in which all food groups are included. The most suitable in this case are those of animal origin. While it is true that there are some foods of vegetable origin that contain it, it is in very low amounts. Therefore, people on vegan and vegetarian diets that do not include any animal foods, or do so in very low amounts, should take supplements to avoid deficiencies.

Beef is one of the foods with the highest amount. Its contribution is 2 micrograms per 100 grams of product; in the case of beef tenderloin, the figure rises to 13 micrograms per 100 grams. Also the chicken breast, especially if it is eaten cooked and skinless; an intermediate-weight breast has about 30 micrograms; a great contribution of this nutrient to the body.

Eggs are also ideal and add variety to the diet. This nutrient is found in the yolk and the intake is 1.3 micrograms per large egg.

Of all dairy derivatives, it is strong cheese, and cured cheese, which provides the most vitamin to the body, 3 micrograms per 100 grams.

In the case of molluscs, octopus is one of the foods with the highest amount of micronutrient; about 20 micrograms per 100 grams.

Of crustaceans, crabs are a fantastic option for achieving adequate blood levels of vitamin B12.

Finally, simply mention a product of vegetable origin rich in this one. Although, as we have explained, its amount of this nutrient is very low and does not meet the needs of the body at all. It is tempeh, or soya fermented, with a tiny contribution but can be used as a complement. Some mushrooms also have a little bit of nutrient.

Cyanocobalamin supplements – Is that the best option?

To ensure normal levels of vitamin B12 in the blood, we strongly recommend taking supplements, always to the right extent; it is a good idea to seek the advice of your doctor or dietitian beforehand.

B12 supplements are especially recommended for two population groups. On the one hand, vegans and vegetarians, who do not consume (or almost) any animal products. As we have pointed out, cobalamin is found in this type of food, so taking supplements to guarantee levels of this nutrient is essential in this case.

The same goes for people with absorption problems in the body. However, in this case, vitamin supplementation will be necessary in direct contact with the bloodstream, which requires a doctor’s prescription.

It has been shown in recent studies that the cyanocobalamin form of B12 is more effective and has a lower risk of producing excess B12 cyanocobalamin than other forms of B12, such as methylcobalamin or hydroxocobalamin, which is why whenever a supplement of this micronutrient is chosen to be chosen in the form of cyanocobalamin.

However, anyone who considers it appropriate can take the following supplements, for which no prescription is necessary: pills, sublingual, drops and spray. They’re all equally effective. The most common is to take weekly tablets, which provide between 1000 and 2000 micrograms, but any format is equally valid.


By way of conclusion, it is essential to say that having normal levels of vitamin B12 is essential for good health in the medium and long term. It is highly recommended to take supplements, in the vast majority of cases, especially among people who do not consume food of animal origin and those with absorption problems. And, of course, it is essential to live a healthy and balanced lifestyle in which a balanced diet is the basis.

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Have you had any tests recently? What were your blood levels of B12? Leave your experience in the comments, together we make an even bigger community!

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