Vitamin B12 Dosage

There are several different forms of vitamin B12. Dosage is based on which form you are taking, why you are taking it, and what other medical conditions you have. For general supplementation purposes, vitamin B12 dosing guidelines are based on Recommended Dietary Allowances (RDAs). The dosages for oral and nasal forms of the vitamin are much higher than for the injectable form.

An Introduction to Vitamin B12 Dosages

The recommended dose of vitamin B12 depends on several different factors, such as:
  • Which form of vitamin B12 you take
  • The reason you take the vitamin
  • Other medical conditions you may have.
As always, do not adjust your dosage without your healthcare provider's approval.
Types of Vitamin B12
There are several different forms of vitamin B12. Injectable vitamin B12 and vitamin B12 nasal spray (CaloMist™, Nascobal®) are prescription-only medications that have been proven safe and effective. Tablets, sublingual ("under the tongue") tablets, capsules, and liquids are alternative forms that are available as non-prescription dietary supplements. Lastly, a vitamin B12 patch is available, but there is little evidence to suggest that this vitamin can be absorbed through the skin.
The dosages for the oral and nasal forms are much higher than for the injectable form, since only a small percentage of the dose for oral or nasal forms actually reaches the bloodstream. It is not clear how much of the vitamin (if any) is absorbed from vitamin B12 patches.
Vitamin B12 Dosing Guidelines for General Supplementation
For general supplementation purposes, the Recommended Dietary Allowances (RDAs) for vitamin B12 are as follows:
0 to 6 months*
0.4 mcg daily
7 to 12 months*
0.5 mcg daily
1 to 3 years
0.9mcg daily
4 to 8 years
1.2 mcg daily
9 to 13 years
1.8 mcg daily
14 years and older
2.4 mcg daily
Pregnant women
2.6 mcg daily
Breastfeeding women
2.8 mcg daily
*RDAs are not established for vitamin B12 for infants under one year old; instead, an "Adequate Intake" level is provided.
For nutrients that can cause toxicity, a "Tolerable Upper Intake Level" (UL) is given. This is the maximum that can be taken from all sources, including the diet, without causing significant toxicity. There are no UL values for vitamin B12, since the risk of toxicity is quite low.
It is recommended that people over 50 years old should get most of their vitamin B12 requirements through supplements, such as a multivitamin, or fortified foods to which vitamin B12 has been added. Older people have difficulty absorbing vitamin B12 naturally found in food, but not the vitamin B12 in supplements or fortified foods.

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Last reviewed by: Kristi Monson, PharmD
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