Vitamin B12 Medium Dose: 100-250 MCG

B12 basic dose 

Vitamin B12 Medium Dose: 100-250 MCG

Vitamin B12 medium dose: calculations of the optimal dose of B12 are set around 250 µg. This amount usually covers the RDA. For whom is it suitable?

Medium Dose Vitamin B12 – The “Regular” Dose

A daily oral dose of 150 – 250 µg is the optimal amount to ensure a sufficient vitamin B12 supply for healthy people, if the supplement is expected to cover the body’s total daily requirement alone. The medium dose is thus particularly well suited for vegans and vegetarians who wish to maintain a healthy B12 supply. 

Supplements containing a medium dose should ideally be taken daily to ensure a steady intake. This gentle and balanced supply corresponds much more closely to the body’s natural absorption pattern than a weekly dose which causes a sudden surge of B12.

Note: this article refers to B12 dosages for oral supplements, the dosage levels for B12 injections can be found in a separate article.

Medium Dose Profile

An oral dose of 150-250 µg vitamin B12 is suitable for those who have:

  • Otherwise good health besides an uncertain B12 intake
  • Relatively good lifestyle – moderate consumption of alcohol/tobacco, relatively healthy nutrition and diet
  • Slight stress in regards to exercise, work, mental health, therapy, sleep
  • Vegetarian or vegan diet
  • Pregnancy

When is a Medium Dose Insufficient?

It is sometimes necessary to take a higher dosage of vitamin B12, particularly for those who suffer from stress or illness, take strong medicines, or have absorption disorders/gastrointestinal impairments (this includes the elderly). For further information here, see our article: Vitamin B12 Increased Dose: 300-500 µg 

For the treatment of a severe B12 deficiency and for those with anaemia/diseases, a high dose of 1000 µg or more is needed. For simply covering the daily requirement, however, this is usually not necessary – even for those who suffer absorption difficulties. For more information on high doses, see: Vitamin B12 High Dose: 1000 – 3000 µg

Covering the Daily Requirement

So, exactly how much B12 do you need to take in order to cover the daily requirement? This is a question that many people ask themselves when searching for the right supplement, however the answer greatly depends on the individual’s ability to absorb the vitamin in the gut. 

The body’s physical B12 requirement is around 1 – 2 µg, but the intake should be significantly higher to keep the body’s B12 stores topped up. The Institute of Medicine (IOMrecommend 2.5 µg (1), current studies suggest 7 µg (2), and the Vegan Society propose 10 µg (3). The actual bodily intake of vitamin B12, however, is not identical to the amount administered, but rather is made up of a combination of factors. As an example, a supply of 10 µg actually only yields around 1.5 µg B12 in most cases. 

Part of the supply is absorbed via a special protein known as the intrinsic factor (IF), whilst the rest is absorbed via passive diffusion through the intestinal wall. Both routes require a healthy stomach and an intact intestinal flora.

Around 1.5 µg of B12 is absorbed via IF per dose, while a further 1% of the dose is taken in through passive diffusion (4). 

In order to achieve an actual intake of 3 µg B12 in one dose, the supply is calculated as follows: a dose of 150 µg = 1.5 µg via IF + 1.5 µg via diffusion = 3 µg

Why Take 150 – 250 µg of Vitamin B12?

As the formula above shows, a dose of 150 µg ensures an actual absorption of 3 µg from a single dose. Given that it is possible for both these methods of absorption to be used somewhat ineffective, a dose of 250 µg provides a generous buffer and should thus be enough for almost all people to cover their daily requirement and additionally top up the body’s vitamin B12 store. This medium dose can thus be seen as the optimum vitamin B12 dosage level for the majority of people. 

For those suffering from stress or minor illnesses – as well as those with an unhealthy lifestyle or who are taking particular prescription medicines – an increased dosage of 300-500 µg per day is recommended, which is a common dose contained in many supplements. 


  1. Institute of Medicine, Food and Nutrition Board, National Academies of Science, Dietary Reference Intakes (DRI): Recommended Dietary Allowances and Adequate Intakes, USA 2018,  
  2. Mustafa Vakur Bor, Kristina M von Castel-Roberts, Gail PA Kauwell, Sally P Stabler, Robert H Allen, David R Maneval, Lynn B Bailey Ebba Nexo „Daily intake of 4 to 7 µg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12–related biomarkers in a healthy young population“ Am J Clin Nutr 2010 91: 3 571-577; First published online January 13, 2010. doi:10.3945/ajcn.2009.28082
  4. 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