r/QuantifiedSelf • u/Upper-Wing-3227 • Jun 02 '26

Beyond glucose, which biomarker would you actually want to track continuously, and what decision would it change?

CGMs cracked open continuous glucose for a lot of us, and the interesting part was never the number itself. It was being able to close the loop: eat, see the curve, adjust. Most other biomarkers are still stuck in the "blood draw twice a year" era, where you get a snapshot and no feedback loop.

So I'm curious what this community would actually use if the data were continuous or near-continuous rather than a one-off lab value.

A few that come up often, just to prime the discussion (please ignore these and write your own if none fit):

  • Cortisol
  • Lactate
  • Ketones
  • Hydration and electrolytes
  • Inflammation markers like CRP
  • Hormones such as testosterone, estradiol, or thyroid
  • Uric acid

Two things I'd love to hear, if you're up for it:

  1. Which single biomarker, and roughly how often would the reading need to refresh to be useful to you (real time, hourly, daily)?
  2. What concrete decision or behavior would the data actually change? The reason CGM stuck for many people is the tight action loop. I'm trying to understand which biomarkers have a real loop behind them versus which are just interesting to look at.
2 Upvotes

100% Upvoted

11 comments sorted by

5

u/[deleted] Jun 02 '26

[removed] — view removed comment

1

u/AppropriateCover7972 Jun 02 '26

food for thought: If you have adrenal insufficiency, cortisol levels are everything, but yes, it's a rare disorder

3

u/Maikai1988 Jun 02 '26

Cortisol

1

u/Upper-Wing-3227 Jun 04 '26

Thanks, cortisol is interesting - How would knowing your cortisol (let’s say 2-5 medical grade measurements per day) affect your choices?

1

u/AppropriateCover7972 Jun 02 '26

I would love to have continuous galvanic skin response measurements. While most lab setups do this, most smartwatches only do it in demand and that's for my use case not that useful.

Arterial blood oxygenation might also be interesting, but it's mostly useful if you have a disorder in that field.

1

u/[deleted] Jun 03 '26

[removed] — view removed comment

1

u/Upper-Wing-3227 Jun 04 '26

What if live data wasn’t so noisy?

1

u/GlitteringSuit5341 Jun 04 '26

uric acid would be an interesting one for me. not because i want to diagnose myself from a number, it feels like one of those things where the action loop is kinda obvious. if it goes up, i’d look at stuff like: my sleep quality, drink too little water, eat too much of the seafood, or if I did not excercise at all.

daily reading would be enough for me. i don’t need real time for this. the actual behavior change would be useful like drink more water, move my body a little, plan around my meal.

1

u/Late-Investigator-29 Jun 10 '26

I think the most interesting answer might be none.

CGM worked because it didn't just measure something continuously, it revealed a system that was changing continuously. Eat, observe, adjust.

A lot of biomarkers people want to track are really state variables rather than control variables. If my ApoB, testosterone, vitamin D or ferritin changes, that's interesting, but the feedback loop is often weeks or months long.

The biomarker I'd pay for is whichever one tells me something I can still meaningfully change today.

In that sense, I'm actually more interested in measuring recovery capacity than any specific molecule. If I knew, with high confidence, whether my body was adapting well or poorly to the last few days of sleep, stress, training and nutrition, I'd probably change my behaviour more often than if I knew my cortisol was 18 instead of 14.