How much vitamin B12 you need depends on how old you are and if you have any illnesses. You need the same amount of B12 whether you take the methylcobalamin or cyanocobalamin form, so to keep things simple we’re going to talk about methylcobalamin dosage here.
After all, we think methylcobalamin is always the better choice!
Recommended Methylcobalamin Dosage
The Recommended Daily Allowance (RDA) of vitamin B12 is set by the Food and Nutrition Board (FNB). If your daily methylcobalamin dosage is above that suggested in the RDA for your age group, then you shouldn’t have a problem. The RDA is a sufficient intake to meet the nutritional needs of about 98% of healthy people.
There isn’t enough evidence to calculate an RDA for infants under a year old, so Adequate Intake levels (AIs) are given instead. These are set at a level that is assumed to meet an infant’s nutritional requirements.
The RDAs and AIs for vitamin B12 are as follows:
- 0.4mcg at 0-6 months old*
- 0.5mcg at 7-12 months old*
- 0.9mcg at 1-3 years old
- 1.2mcg at 4-8 years old
- 1.8mcg at 9-13 years old
- 2.4mcg at 14+ years old
- 2.6mcg for pregnant women
- 2.8mcg for breastfeeding women
*These figures are AIs. All other figures are RDAs.
You may also see these figures written with μg instead of mcg. Either way it means micrograms i.e. 1/1000th of a gram – a microscopic yet medically significant quantity.
Upper Tolerable Index Level
The Upper Tolerable Index Level is the maximum amount of a substance that can be consumed in a single day with no adverse health effects. Vitamin B12 and methylcobalamin do not have an UTIL as there is no evidence that high levels of B12 are harmful.
You cannot overdose on vitamin B12 and it has vanishingly low toxicity. No matter how high your methylcobalamin dosage is, any excess will simply be excreted out in your urine because B12 is a water-soluble vitamin.
You can read more about this in our B12 Overdose & Side Effects article.
Methylcobalamin Dosage in Supplements
Most young and healthy people do not need to take methylcobalamin supplements, but there are plenty of people who do. Vegans and vegetarians, people suffering from a number of gastrointestinal disorders and anyone over the age of 50 should take B12 supplements.
If you don’t eat meat, you generally won’t be getting any vitamin B12 in your diet. You can increase your intake by eating fortified cereals, but that will rarely be enough on its own. That means you need to reach your RDA by taking regular vegan methylcobalamin supplements.
Don’t be fooled by the huge quantities of B12 found in supplements. Just because it contains 80,000% of your RDA doesn’t mean you can take one tablet every two years and stay healthy! Recent studies have shown that only around 10mcg of a 500mcg oral supplement will actually be absorbed in healthy people.
This means that a weekly 1000mcg methylcobalamin supplement should probably be enough to ensure adequate B12 intake. However, many vegetarians and vegans take higher dosage supplements and/or take them more often. There is no harm in this, so you may as well go for it if you want to be absolutely certain you’re getting enough B12.
Methylcobalamin Dosages With Impaired Absorption
People with gastrointestinal problems and many older people struggle with the same problem: neither group are able to absorb enough vitamin B12 from their diets (albeit for different reasons). This would traditionally have been treated with B12 injections, but modern high-dose oral supplements have made that unnecessary.
Many over-50s suffer from a condition where the body no longer produces enough of a protein called intrinsic factor (IF), which is essential for vitamin B12 absorption. The methylcobalamin dosage in some supplements is enormous compared to the RDA, but a lack of IF means lots of older people have to rely on passive diffusion in the gut to absorb B12 into their bodies. This means that the vast majority of the supplement does nothing, with only about 1% being absorbed passively. Therefore even 1000mcg supplements would need to be taken at least two or three times per week – and 5000mcg supplements would be even better. Some will even take these every day to be on the safe side.
Sublingual tablets may be a better solution, as these bypass the gut and allow B12 to be absorbed into the bloodstream directly. This effectively increases the methylcobalamin dosage you receive from the same strength supplement. However, the research so far is inconclusive, and the battle between oral and sublingual supplements is still hotly contested.
Vitamin B12 Deficiency
For people who have already been diagnosed with vitamin B12 deficiency, a course of methylcobalamin supplements should begin immediately. A large methylcobalamin dosage will be required every day at first, gradually reducing frequency over time. This ensures your B12 levels recover as quickly as possible, prevents you from sliding back into deficiency, and also ensures you won’t be taking pointless extra supplements when your B12 levels are back to normal.
1000mcg tablets have proven to be very effective, given every day initially. When B12 levels improve, the tablets can be taken every few days instead, and then once per week to maintain a healthy level.
If you’d like to see the methylcobalamin supplements we recommend, check out our Recommended Supplements page!