Vitamin B12 half-life
Vitamin B12 is a water-soluble vitamin (cobalamin), but unlike most water-soluble vitamins it is stored in the liver. It clears the bloodstream in about a week, while its whole-body half-life is roughly 400 days because those liver stores turn over very slowly. Since B12 accumulates and persists for years, it does not have to be taken daily to keep body levels up.
What a half-life actually means
A half-life is the time it takes for half of what is in your blood to be gone. It does not mean the compound is finished at that point. Half goes, then half of what is left goes, and so on.
That is why the last traces take so much longer to disappear than the first. Most references treat something as effectively cleared after about five half-lives, which for Vitamin B12 is roughly 285.7 weeks.
How Vitamin B12 clears
| Half-lives | Time since dose | Roughly left |
|---|---|---|
| 1 | 57.1 weeks | 50% |
| 2 | 114.3 weeks | 25% |
| 3 | 171.4 weeks | 12.5% |
| 4 | 228.6 weeks | 6.25% |
| 5 | 285.7 weeks | 3.125% |
These are round numbers from a single half-life figure. Real clearance shifts with dose, body composition, liver and kidney function, and what else you are taking. Treat it as a shape, not a schedule.
Why the timing matters
A short half-life means levels swing between doses, so timing and frequency do most of the work. A long half-life means levels build for days or weeks before they settle, so a change you make today might not show up for a while, and stopping does not clear things straight away.
Vitamin B12 sits at about 57.1 weeks, so it behaves like the long end of that range.
See your own levels, not a table
NextDose models your actual blood level from the doses you log, then calibrates the curve to your bloodwork. Built on 30,000+ research papers, clinical trials and FDA records.
Get NextDose.AIWhen levels level off
On a repeating schedule the amount in your body climbs until what you take in each interval matches what clears in it. That plateau is called steady state, and it arrives after roughly five half-lives whatever the dose. For Vitamin B12 that is about 285.7 weeks of consistent dosing.
The typical starting schedule is 1x daily (sublingual), at 500 mcg/day. Until that plateau, every dose lands on top of more of the last one than it will later, which is why the first weeks of a protocol can feel different from the same dose a month in.
Skipping doses resets part of that climb. One missed dose costs roughly one half-life of accumulation, so the shorter the half-life the more a gap matters.
Mixing and measuring Vitamin B12
Oral tablet/sublingual or injectable solution
Store at 15-25°C (room temp). 2 years sealed.