Selenium half-life
Selenium is stored in tissue for a very long time. This form (selenomethionine) has a whole-body half-life around 250 days, so it builds up slowly and clears slowly. Because it accumulates for the better part of a year, it's easy to over-supplement without realising.
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 Selenium is roughly 178.6 weeks.
How Selenium clears
| Half-lives | Time since dose | Roughly left |
|---|---|---|
| 1 | 35.7 weeks | 50% |
| 2 | 71.4 weeks | 25% |
| 3 | 107.1 weeks | 12.5% |
| 4 | 142.9 weeks | 6.25% |
| 5 | 178.6 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.
Selenium sits at about 35.7 weeks, so it behaves like the long end of that range.
See your own levels, not a table
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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 Selenium that is about 178.6 weeks of consistent dosing.
The typical starting schedule is 1x daily, at 100 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 Selenium
Oral capsule — no reconstitution
Store at 15-25°C (room temp). 2 years sealed.
Research mentioning Selenium
Indexed records from PubMed and ClinicalTrials.gov that reference Selenium. These are here so you can read the primary material yourself. They are not the source of the half-life figure above.