Vitamin B12 Increased Dose: 300-500 MCG

Extra B12 requirement 

Vitamin B12 Increased Dose: 300-500 MCG

Vitamin B12 increased dose: 300-500 µg of B12 covers the daily requirement even for mild absorption disorders. Useful for stress, illness and in old age.

Increased Dose of B12 – Covering the Daily Requirement with an Increased Need

A daily oral dose of vitamin B12 between 300 – 500 µg can cover the body’s daily requirement in cases where it has been increased – for example, due to malabsorption, gastro-intestinal disorders or for the elderly (1). Since malabsorption is unfortunately quite common nowadays – as a result of widespread poor intestinal health, high levels of stress and unhealthy lifestyles – this dosage has become the option of choice in many cases to prevent B12 deficiency and to ensure that the many benefits of B12 are obtained.

Increased Dosage Profile

An increased dose of 300 – 500 µg is the correct choice for people who are:

  • Elderly
  • Suspect that they have suboptimal absorption
  • Breastfeeding mothers
  • Suffering from a long-term B12 deficiency
  • Regularly taking medicine 
  • Experiencing physical, emotional or mental stress
  • Undertaking a spiritual transformation and/or personal upheaval
  • Subject to rigorous sport and athletic activity
  • Suffering or recovering from a disease
  • Experiencing a high workload (physical and mental)
  • Living an unhealthy lifestyle (e.g. smokers, heavy drinkers)

The Complex Intake of Vitamin B12

According to the Institute of Medicine (IOM), the daily vitamin B12 requirement for adults is 2.5 µg (2). If an oral supplement is designed to cover the whole daily requirement however, the dose has to be considerably higher than this figure, due to the way in which the body takes in vitamin B12. There are two absorption pathways for B12 (3):

  1. Via the transport protein known as intrinsic factor (IF) – up to 1.5 µg per dose
  2. Through passive diffusion in the intestinal wall – roughly 1% of the dose

When vitamin B12 is obtained from foods, it is typically taken in many small doses throughout the day, allowing the IF route to be maximised each time. In the case of a B12 supply via supplements, however, a dosage should be chosen to cover the daily requirement in such a way that a single dose is enough.

Assuming that the body’s absorption is optimal, a single dose of 100 µg will cover the entire recommended dietary intake:

1.5 µg + 100 µg /100 = 1.5 + 1 = 2.5 µg

Vitamin B12 Supply and an Increased Requirement

Unfortunately, many people have an impaired vitamin B12 intake, due to insufficient IF production, stomach or intestinal problems. Additionally, many life circumstances also require an increased supply of the vitamin (see the list above). In these cases, a dose of 300-500 µg is necessary. Any dose above 300 µg is enough for passive diffusion alone to meet the daily requirement – very useful for people who are lacking in intrinsic factor. 

Since it is possible for both means of absorption to work inefficiently, many B12 supplements today simply contain 500 µg. This dosage contains a good buffer to take into account fluctuations in the intake capacity and is sufficient to cover the demand even in the case of many absorption disorders.

When is this Increased Dose Insufficient?

A dose of 1000-3000 µg is used for those suffering from severe B12 deficiency with anaemia, as well as in the treatment of certain illnesses. More information on this can be found in our article: Vitamin B12 High Dose

Extra Vitamin B12 for an Increased Requirement

A vitamin B12 dose of 300-500 µg offers the necessary extra vitamin B12 to cover an increased need. Readers who fit the above profile are well advised to take this dosage. Higher dosages than this are only really necessary in specific therapeutic contexts; the increased dose between 300-500 µg is sufficient for most people. 


  1. Park, S. and Johnson, M. A. (2006), What is an Adequate Dose of Oral Vitamin B12 in Older People with Poor Vitamin B12 Status?. Nutrition Reviews, 64: 373–378. doi: 10.1111/j.1753-4887.2006.tb00222.x
  2. Institute of Medicine, Food and Nutrition Board, National Academies of Science, Dietary Reference Intakes (DRI): Recommended Dietary Allowances and Adequate Intakes, USA 2018,  
  3. 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