Vitamin B12 High Dose: 1000-3000 MCG

Large B12 Dosage 

Vitamin B12 High Dose: 1000-3000 MCG

When is a high vitamin B12 dose of 1000-3000 µg necessary? Can a high dosage be dangerous? How much B12 do I need to meet my RDA?

Vitamin B12 High Dose

High dose vitamin B12 can be necessary for sufferers of malabsorption or diseases. Dosages of this level are very useful in treatment and provide a great help for a variety of diseases. Doses of over 600 µg are additionally often necessary for the elderly, whose absorption is no longer optimal.1

It is important to remember that a medium dosage of 150-250 µg is sufficient for most people as a food supplement to cover the body’s daily requirement. Additionally, all the information given in this article relates to oral supplements – dosage levels for vitamin B12 shots are covered in a separate article.

When is Taking High Dosage Vitamin B12 Worthwhile?

The basic doses offered in many vitamin B12 supplements are enough to cover the vitamin B12 RDA for the majority of users. People suffering diseases or with a severe vitamin B12 absorption disorder are often advised, however, it take vitamin B12 in high doses. The term ‘high dose’ here means a vitamin B12 dosage of around 1000 µg. This corresponds to over 30,000 % of the official recommended 3 µg daily dosage given by the DGE, which suggests to be a massive overdose.

However, the actual intake of vitamin B12 is a much more relative figure: of the 1000 µg taken in one oral dose, a maximum of 12 µg is actually absorbed by the body – which is only around 400 % of the recommended dietary allowance per day.2

When Does it Make Sense to Take Such Doses?

On the whole, these doses are reserved for use in treatment therapy. In the very elderly, dosages of 600 µg and upwards have proven to result in a complete normalization of the body’s B12 levels.The reason for this: in old age, the body’s ability to absorb and utilize vitamin B12 is typically very impaired for a number of reasons. This means that the body requires very high doses in order to effectively absorb the required amount of vitamin B12 to be used.

Absorption Problems and High Dose Vitamin B12

Such intake disorders and absorption difficulties are typically caused by:

  • Inflammations of the stomach, the intestine and/or the pancreas
  • Intestinal surgery
  • Interactions with medicines or drugs
  • Nutrient deficiency (e.g. calcium)
  • Fungal or bacterial infection in the intestine or similar

In these cases, an oral dosage in the region of 1000-3000 µg can be the only way to ensure that the body’s vitamin B12 needs are met. Often in these scenarios it is also worth referring to vitamin B12 injections, as they simply bypass the impaired intestinal passage.

High Dose Vitamin B12 as a Weekly Dose

Another method of taking vitamin B12 which is commonly recommended in the US is to take one weekly dosage of 2000 µg to theoretically cover the body’s need for a whole week, removing the need to meet the body’s daily requirement with small, daily doses. This use is very similar to the way that vitamin B12 injections function.

Naturopaths tend to recommend small doses at regular intervals as opposed to large, irregular doses, as this corresponds most naturally to the body’s natural absorption of vitamin B12 and allows a steady and balanced supply. This is perhaps more manageable for the body than the sudden surge provided by a large dose.

High Dose Vitamin B12 in Profile

High dose vitamin B12 is useful in the following circumstances:

  • Severe absorption difficulties (see above)
  • Initial therapy for refilling the body’s B12 store after an acute deficiency
  • Therapeutic uses (nerve disease, dementia, severe depression, etc)
  • Intake as a weekly dose

Is it Dangerous to Take a High Dose of Vitamin B12?

Vitamin B12 is considered harmless, oral doses of up to 5000 µg have been clinically proven to show no acute side effects. However, it is important to be aware that the body is a sensitive system, and thus in the long-term, an excessive supply of micronutrients could lead to a stark imbalance between nutrients in the body, which could have very negative effects.

‘The more the merrier’ is generally viewed to be incorrect in micronutrient medicine – it is considerably better to find the optimal dose for each individual case. A high dose intake of vitamin B12 as a preventative is in the best case a waste of time for most people – the vitamin is simply excreted through urine without being utilized.

Therefore, it is important to ensure consideration before taking a high dose of vitamin B12 – many people will find an  increased dose of 300-500 µg caters much better for their needs.


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.

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