Suggested Doses of Oral B12 Supplements
If possible, please discuss any treatment with your doctor first. There are some conditions, possibly including intestinal bacterial overgrowth, in which oral vitamin B12 supplements have been reported to be ineffective.
The correct dose of oral vitamin B12 supplements will depend on what you need to do:
- Build up vitamin B12 Stores
- Maintenance
To find out more about oral vitamin B12 doses, I suggest that you read references FA01, FA02 and FA04; there are links to these articles on the References page.
Build up vitamin B12 Stores
If you have been diagnosed with vitamin B12 deficiency, and choose to rebuild depleted stores using oral vitamin B12 supplements, you need to take very large doses for at least the first few months.
Even a person with pernicious anaemia is usually able to absorb about 1% of any oral vitamin B12 dose. If you take a dose of 1000µg, you should absorb about 10 µg by passive diffusion. This is four times the recommended daily intake, and allows sufficient excess for storage.
A healthy person can only absorb a maximum of about 10 µg from any one dose, regardless of the size of the dose. The total body store in a healthy person is approximately 2-3mg.
For most people, a dose of 1000 µ will therefore provide an effective 10 µg intake; this is sufficient to rebuild the body stores after about 200 doses.
If you take two doses of 1000 µg each, for 100 days, your stores should be filled at the end of that time.
It is absolutely essential that you monitor your B12 stores during this time, by measuring serum B12, to ensure that you are absorbing the oral vitamin B12.
Maintenance
The size of the maintenance dose depends on the cause of the deficiency.
A healthy vegan only requires a very small maintenance dose of at least the recommended daily intake. This is available in multivitamin capsules, where typically about 10-50 µg of cyanocobalamin is included.
For any other person who has a vitamin B12 deficiency, unless you are certain that you have only a mild malabsorption, it is best to err on the side of safety. A single daily dose of 1000 µg should provide an effective intake of 10 µg, more than adequate in most cases
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