Vitamin B12 High Dose: 1000-3000 MCG


Vitamin B12 High Dose: 1000-3000 MCG

Vitamin B12 high dose: when is it necessary to take B12 doses between 1000-3000 µg? When is less enough? Can high doses be damaging or even dangerous?

High Dose Vitamin B12

High dose vitamin B12 of around 1000 µg per day is needed if there is an increased requirement, due to a number of factors that we will discuss below, or if B12 deficiency is suspected. It also plays a role in the treatment of a whole range of diseases. 

Since B12 is a water-soluble vitamin, there is no danger of overdose when a high dose is administered; only a small portion of the dose is actually absorbed by the body.

In essence, high dose B12 is useful in treating a deficiency. For healthy people, a B12 dosage of between 250 – 500 µg will safely cover the daily requirement. It should be noted that this information refers to oral supplements – the dosage of vitamin B12 injections is discussed in a separate article.

When is B12 Considered to be High Dose?

A vitamin B12 dose of 1000 µg or more is considered high. This corresponds to over 40 000% of the daily requirement of 2.5 µg officially recommended by the Institute of Medicine (IOM), which initially appears to be an enormous overdose.

However, this impression is put into perspective if you consider the actual intake: from the 1000 µg, only a maximum of 12 µg is actually absorbed by the body with a single oral dose; only 480% of the daily requirement (2). 

When is it Useful to Take High Dose B12?

There are four instances in which it makes sense to take vitamin B12 in this high dose range:

  1. As initial therapy for severe deficiency 
    (to replenish the body’s stores)
  2. For those with a significantly increased requirement
    (e.g. breastfeeding women, people with severe stress, those suffering from infections, athletes)
  3. Due to malabsorption
    (e.g. old age, interaction with medicines, gastrointestinal problems)
  4. In the case of various diseases
    (nerve disorders, mental illnesses, intestinal diseases)

For the majority of all other applications and maintenance therapy, a dose of up to 500 µg is usually sufficient.

Vitamin B12 Initial Therapy

In the initial treatment of vitamin B12 deficiency, the vitamin is supplied in high doses in order to quickly replenish the body’s stores. Here, the dose must not only cover the daily requirement, but also provide sufficient additional B12 to replenish the body’s stores of the vitamin.

This can be achieved with doses from 1000 µg. However, we recommend using even higher dosages of 5000 µg. In this way, the treatment period is drastically reduced.

Increased Requirement

There are different factors which increase the vitamin B12 requirement. Among the most important are:


This can be caused by: 

  • Old age
  • Inflammation of the stomach, intestines and/or pancreas
  • Intestinal surgery
  • Interactions with medicines or drugs
  • Nutrient deficiencies (e.g. calcium)
  • Fungal, parasite or bacterial infections in the intestine

With age, the absorption ability decreases. Therefore, B12 markers do not completely normalise in older people unless daily doses between 500-600 µg or more are administered (3). This is an average value and in individual cases significantly higher doses may be necessary, which is why a dose of 1000 µg has also proven to be effective here.

In the other named cases, an oral dosage of vitamin B12 in the range of 1000-3000 µg is the only possibility to cover the requirement. Often, however, vitamin B12 injections are used to avoid the unreliable route of absorption through the intestines.

Vitamin B12 and Diseases

Today, high-dose vitamin B12 is used in the treatment of various diseases. These include in particular:

  • Anaemia 
    (pernicious anaemia)
  • Mental illnesses
    (depression, psychosis, schizophrenia etc.)
  • Neurological diseases
    (neuropathies, nerve disorders, dementia etc.)
  • Chronic systemic diseases
    (chronic fatigue, fibromyalgia etc.)

Especially in the field of mental and neurological diseases, very good results can be achieved with high doses of vitamin B12.

Finding Suitable Supplements Online

Application DosageActive Ingredient Online Search
Initial therapy5000 µgHydroxocobalaminHydroxocobalamin + high dose + depot + 5000 µg
Absorption disorder,
increased requirement, disease 
1000 µgMethyl-, adenosyl- and hydroxocobalaminB12 + methylcobalamin + adenosylcobalamin + hydroxocobalamin + 1000 µg + bioactive  

High Dose Vitamin B12 as a Weekly Dose

Another application is frequently recommended, especially in the USA: instead of covering the daily requirement with small daily doses, a large dose of 2000 µg can theoretically meet the B12 requirement for a whole week, if health is optimum. The procedure for vitamin B12 injections is very similar.

Naturopaths tend to recommend a regular intake of small doses that corresponds to the natural intake of B12 and ensures an even supply, which they believe may be easier for the body to cope with than intermittent flooding with large doses.

Profile: High Dose Vitamin B12

In summary, vitamin B12 in high doses can be useful for:

  • People with malabsorption
  • Those with an increased requirement
  • Initial therapy to replenish the body’s stores following an acute deficiency
  • Therapeutic application (nervous diseases, dementia, severe depression, etc.)
  • Intake as a weekly dose

Is it Dangerous to Take High Doses of Vitamin B12?

Vitamin B12 is considered harmless. Clinical trials, which tested oral doses of up to 5000 µg showed no acute side effects. Nevertheless, it should be noted that the body is a sensitive system; an excessive intake of micronutrients over time may disturb the nutrient balance, which can lead to very negative effects.

“More is more” is generally not the right approach to take with micronutrient medicine – rather the optimal dose for each individual case should be carefully determined. A high dosage of vitamin B12 for prophylaxis is probably pointless for most people, as the vitamin is excreted through the urine anyway.

High dose vitamin B12 only makes sense in the cases mentioned above; most people will be sufficiently supplied with an increased dose of 300-500 µg.


  1. Eussen SM, de Groot LM, Clarke R, et al. Oral Cyanocobalamin Supplementation in Older People With Vitamin B12 Deficiency: A Dose-Finding Trial. Arch Intern Med. 2005;165(10):1167-1172. doi:10.1001/archinte.165.10.1167
  2. Berlin, H., Berlin, R. and Brante, G. (1968), Oral Treatment Of Pernicious Anemia With High Doses Of Vitamin B12 Without Intrinsic Factor. Acta Medica Scandinavica, 184: 247–258. doi: 10.1111/j.0954-6820.1968.tb02452.x
  3. Eussen SM, de Groot LM, Clarke R, et al. Oral Cyanocobalamin Supplementation in Older People With Vitamin B12 Deficiency: A Dose-Finding Trial. Arch Intern Med. 2005;165(10):1167-1172. doi:10.1001/archinte.165.10.1167.