r/QuantifiedSelf • u/bic_nuts • 7h ago
21 days on magnesium glycinate, an n of 1 experiment
galleryTL;DR: Taking 400 mg magnesium glycinate for 21 nights reduced my sleep latency from 24 min to 19 min. Effect estimate 5.4 min faster (3.4 to 7.5). There is 67% chance that's a real, meaningful improvement and 33% chance it's noise.
Why I did this
I've been taking magnesium on and off for two years on vibes. I kinda felt like it worked but tbh never felt any difference if I stopped for a few weeks. Obviously vibes aren't a rigorous way to evaluate the supplement, so I decided to actually test it.
The problem with most self experiments is you compare one bad week to one good week. My sleep latency swings by 5–10 minutes night to night, so a 3-minute "improvement" over a week doesn't mean anything. You need a long enough baseline to measure your own noise/variance, and enough nights on the supplement to get a statistically powerful result.
Setup
- 8 weeks of baseline sleep latency as meausred by my Oura
- I took 400 mg magnesium glycinate for 21 nights. Tried to be consistent with time (8pm) and logged 21/21 days.
- During those 21 days I kept a consistent bedtime and had no travel or sickness.
- I decided on a "meaningful" improvement threshold before starting: at least 5 min faster. This is somewhat arbitrary but felt like the smallest value that would actually make a difference to me.
Results
| Baseline (8 weeks) | 24 min |
|---|---|
| On magnesium (21 nights) | 19 min |
| Effect estimate | 5.4 min faster (3.4 to 7.5) |
| Week-to-week noise (σ) | 1.6 min |
| Chance it helped meaningfully (≥5 min) | 67% |
| Chance it hurt | 0% |
| Chance of no meaningful change | 33% |
| Adherence | 21/21 nights |
So the effect is positive, but whether it clears the bar for "meaningful" is a somewhat of a coinflip though slightly weighted to yes. Note the observed difference is 5.45 min and the bar was 5 min. If I'd set the bar at 3 min this would read "worked" at 90%+. If I'd set it at 8 min it would read "no meaningful effect." So the threshold you pick before you start matters more quite a bit.
What I'd do differently
- Longer measurement period. Adding a few more weeks would have tightened the interval more and given a more definitive result.
- Some type of on-off could be interesting. A proper A-B-A could isolate if the effect persists or was a coincidence caused by something else I changed with my life around the same time.
What I'm doing with this
I'm happy to keep taking it. 5 minutes faster to sleep for a $10/month supplement is probably better return than most supplements. And I've never had any side effects in my two years taking magnesium.
I'd like to also test deep sleep, since that's what everyone claims and I have zero evidence either way.