5HT #108: what I do + don’t do in early prevention

I’m prettty sure I was among the first 100 Function Health members, which probably tells you something about my relationship to testing 😅. I'm pro-information and an early adopter… and sometimes embarrassingly so!

After all, testing has helped me understand my body better and feel more sympathetic toward it. It’s helped me adapt my habits, rethink my supplement stack, and finally take things like sleep more seriously.

But the strongest case for my pro-information bias is also the most personal one: a Function panel and the cardiac workup that followed caught my PVCs at 27% burden, which led to the ablation I had in January. Testing didn't just inform me—it found something serious and helped me fix it. That's the version of preventative screening that actually works.

Buuut not every test works that way. The loudest legitimate argument against early screening isn't false positives, but overdiagnosis 📢. The textbook example: in the early 2000s, South Korea introduced widespread thyroid ultrasound screening. Thyroid cancer diagnoses jumped roughly 15x. Thyroidectomies followed. Unfortunately, mortality didn't budge. The tests were finding real cancers… they just weren't cancers that were going to kill anyone. 😕

That's the failure mode I'm trying to avoid, especially as a dad of two little girls who would prefer not to spend the next 40 years chasing unnecessary biopsies and incidental Prenuvo findings… but also want to be there for them as long as humanly possible (or Bryan Johnson possible). So my framework isn't "more is better." It's what frequency, which tests, and what I would actually do with the result.

And while I can’t give pointed advice on which tests to take (I’m not a doctor and none of this is medical advice… think of me as your friend with health benefits 🤓), I can share which early preventive tests I do/don’t do and why.

Function Health 
👩🏻‍🔬 Type of test: Biomarkers
🔎 Why: Twice a year, actually. The single most useful test in my preventative stack, both for general biomarker tracking and for following my cardiac numbers after my heart ablation.

Full-body dermatology skin check
👩🏻‍🔬 Type of test: Doctor’s visit
🔎 Why: Boring, cheap, takes 20 minutes, and one of the rare cancer screens with actual evidence behind it. If you're going to add one test to your annual list beyond getting your blood done, make it this one.

DEXA scan
👩🏻‍🔬 Type of test: Imaging
🔎 Why: I'm actually doing this quarterly right now (thanks to BodySpec) to track my body comp given my GLP-1 microdosing and current health goals to reach 15% body fat (once I land it, this drops back to annual).

Prenuvo / Ezra
👩🏻‍🔬 Type of test: Full-body imaging
🔎 Why: Ezra (wrote about my experience here) confirmed no cancer and flagged my degenerating spine, which sent me back to PT. Prenuvo (wrote about my experience here) I did partly out of curiosity to compare against Ezra (this was before Function acquired it). But I found the Prenuvo experience and readback way better—and plan to do it again in the future as a check up (especially when it comes to Austin!) every couple years.

Eye exam
👩🏻‍🔬 Type of test: Doctor’s visit
🔎 Why: Just had my first one in years. I'm not making this annual yet, but a 2-year cadence going forward feels right. The retina is the one place in the body where you can see blood vessels directly, and it's a surprisingly good check on cardiovascular and neuro health, not just vision.

Toxin Zoomer
👩🏻‍🔬 Type of test: Toxicity panel
🔎 Why:  I went big on this one—probably too big (wrote about it here). My panel was drawn shortly after two procedures, which produced an inflammatory artifact that wasn't meaningful (exactly the kind of noise frequent testing creates). It also flagged things that may be lingering from the ablation, which was useful. The way I see it, our environment is full of toxicity, so getting tested feels like it’ll only continue to get increasingly important. Going forward, I'll run it every couple of years.

pTau-217 blood test
👩🏻‍🔬 Type of test: Blood test
🔎 Why: This established my baseline for Alzheimer's risk given the APOE4 status. Will retest periodically as part of the broader cognitive-risk tracking plan.

NeuroAge Tech
👩🏻‍🔬 Type of test: Imaging, screening, etc.
🔎 Why: This is a new, interesting “brain age” diagnostic I was recently introduced to and completed. It’s an aggressive neuro-age workup with a brain MRI and a genetic panel, anchored on Alzheimer's prevention. (Full breakdown coming soon!) Now that I’ve set a baseline, my plan’s to retest this periodically, too.

23&Me
👩🏻‍🔬 Type of test: Genetic testing
🔎 Why: My test taught me that I carry one copy of the APOE4 allele, which pushed me to go hard on Alzheimer’s prevention. It also flagged two more variants worth acting on, HFE H63D (basically means I likely over-absorb iron) and MTHFR C677T + A1298C (means impaired methylation, which is very common, and I wrote about it here).

Sleep study
👩🏻‍🔬 Type of test: Doctor’s visit?
🔎 Why: I haven't done one yet and think I’m good, but many aren’t. WHOOP and Eight Sleep give me good signals on duration and structure—and there’s no evidence I have sleep apnea. But it’s fairly common and missed constantly and worth considering.

Galleri
👩🏻‍🔬 Type of test: Multi-cancer detection
🧐 Why: I want this category to work. If I could meaningfully track cancer through blood, I would do it. But the recent trial results were a bomb.The test isn't ready, and the deeper issue is that MCED is genuinely hard. Catching "cancer" earlier only matters if the cancer was going to kill you and the treatment changes that outcome. Both halves of that sentence are doing more work than the marketing admits. I'll revisit when there's a study showing mortality benefit, not just detection rate.

Viome / TinyHealth 
👩🏻‍🔬 Type of test: Microbiome stool testing
🧐 Why: I did Viome 2x early in its history (we’re talking 2010s) and found it a bust both times. It presented vague recommendations, arbitrary food lists, and scores that shifted enough between tests I questioned what I was tracking. Tests like TinyHealth are more promising because of improved sequencing, but even that doesn't fix the deeper problem: the field hasn't established a target for a "healthy microbiome." A 2026 study ran identical homogenized stool samples through seven DTC services and found major variability between providers. The same sample got classified as "healthy" by two providers and "unhealthy" by a third; three flagged C. difficile, four didn't. Same poop, wildly different verdicts. To be clear, I'll happily poop in any box… as long as microbiome-test recommendations are shown to change something that matters!

TruDiagnostic TruAge / TallyAge / Generation Lab
👩🏻‍🔬 Type of test: Epigenetic age tests
🧐 Why: The science seems real, and I’m definitely intrigued by the concept of epigenetic organ clocks , but I'm not convinced I'd know what to do with the number. So far, I've skipped—though I'll may try one eventually out of curiosity (and also because, if the result is bad, I'd want to know). Open to changing my mind on this one.

VO₂ max
👩🏻‍🔬 Type of test: Measures the max amount of oxygen your body can use during intense exercise
🧐 Why: I wrote about this and won't relitigate the whole argument here. TL;DR: I don't think the case is as strong as the longevity crowd makes it sound. Eric Topol's pushback is convincing: most of the mortality data attributed to VO₂ max is actually built on METs, and high VO₂ max correlates with a stack of other healthy behaviors that may be doing the real work.

Most of the tests I’ve taken fall into two categories: genuine curiosity and genetic risk. The curiosity ones are useful, but the genetic risk ones are why I do this at all. Knowing I'm APOE4 positive has been one of the most empowering pieces of information I've ever gotten—not because it scared me, but because it gave me a 30-year head start on a disease that doesn't show symptoms until it's too late to do much about it. 

That's the bar for me. A test is worth running if the result would change what I do, what I eat, what I take, what I screen for next, or how I plan the next 20 years. If it wouldn't—even if the dashboard is gorgeous—it's not really a test and more like an expensive souvenir.

👋 Who are you again? I’m Derek Flanzraich—founder of two venture-backed startups in Greatist (👍) and Ness (👎). I’ve worked with brands like GoodRx, Parsley, Midi, Ro, NOCD, and Peloton. I now run Healthyish Content, a premium health content & SEO agency (among other things).

Every Thursday (and now Sunday!), I share healthyish things I feel strongly about. (Disclaimer: I’m more your friend with health benefits. None of this is medical advice.) Also some links are affiliate links, but they influence my decisions zero.

Oh, you also feel strongly about some health things? Hit reply—I’d love to hear it.