★ What 18 Months of Testing Actually Revealed
- ✓Both platforms deliver what they're designed to: comprehensive bloodwork, trend data, general recommendations. That's genuinely useful. It's also not the same thing as a protocol.
- ✓After 18 months and roughly $1,200 in testing fees, the symptoms that sent me to these platforms were still there. Ferritin improved. Vitamin D improved. Blood pressure kept doing its own thing. The other symptoms stayed right where they were.
- ✓That pattern — numbers improving on paper, nothing changing that actually matters — has a specific upstream cause. It took going back to the primary literature to find it.
- ✓It sits in the nitric oxide pathway. Specifically, a compound called ADMA that accumulates over time and blocks the primary route your arteries use to produce nitric oxide. When it's elevated, L-arginine and citrulline do almost nothing. You're feeding a pathway that's already locked upstream. Standard panels don't test for it.
- ✓The tell: if you've run a nitric oxide stack and the initial response faded, that's the pattern. The supplement arrived at a locked door every time.
- ✓There's a second pathway for nitric oxide production that doesn't use eNOS and isn't affected by ADMA at all. Men whose first pathway is blocked can still get meaningful NO production through this route. That's what the standard stacks aren't targeting.
- ✓Once I understood the mechanism, the protocol changed. So did the results. That's what this review covers.
This review isn't going to be balanced for the sake of sounding fair. I used InsideTracker and Function Health as a paying customer for about 18 months, I know what they're good at and where they fall short, and I ended up somewhere different because of a specific gap they couldn't close. That's what this is about.
The gap is in vascular health. Your vascular health covers how well your arteries are actually functioning: blood pressure regulation, blood flow to your muscles and organs, the flexibility of your artery walls, and the capacity of the blood vessel lining to produce the compounds that keep everything working the way it should. Erectile function sits in this same category. It depends on blood flow through small arteries, and it's often the first place men notice something has changed, years before a blood pressure number becomes a problem. The two are linked at the mechanism level.
There's a specific metric that gets closer to the actual state of the arterial system: vascular age. It's distinct from your calendar age. A 47-year-old man can have the arterial function of someone 38 or someone 58. The number that tells you which one he is doesn't come from a standard lipid panel. It requires a different category of markers entirely. Neither InsideTracker nor Function Health measure it, and neither builds a protocol around it.
I'll cover what those 18 months of testing showed me, why I ended up somewhere else, and what finally moved the markers.
What these platforms actually deliver
InsideTracker and Function Health are built around the same core premise: comprehensive bloodwork, visualized clearly, with general recommendations attached to each flagged marker. They do this well. InsideTracker covers 63 to 170 biomarkers depending on your tier, Function Health runs over 100. Both give you longitudinal trend data and flag what's out of range.
The recommendations are reasonable. Add magnesium. Improve your protein quality. Prioritize sleep. None of that's wrong. It's also roughly what a well-informed GP with 20 minutes to spare would tell you, which is more or less the category these platforms occupy.
What they don't do is tell you which mechanism is driving your specific pattern of results. They surface numbers and attach general guidance to each one. There's no protocol built around your individual vascular age and health profile. That distinction matters more than it might sound.
Why I started tracking in the first place
I started on InsideTracker in early 2024. I was 47. Blood pressure had been drifting upward since around 45, nothing alarming on paper, but moving in a direction I didn't like and hadn't moved back despite the usual adjustments. Energy had a lower floor than it used to. And the morning erections that had been consistent since my mid-30s were becoming intermittent. I knew enough about the research to know that last one isn't just an aging thing. That's a blood flow signal.
I'd been paying attention to this stuff for a while. I'd read Attia, followed the r/PeterAttia threads, spent time on ExcelMale long enough to recognize the regulars. I thought I had a decent sense of what the markers were and what I was looking for.
What I was actually looking for, it turned out, wasn't in any of the panels I was running.
18 months of panels, no protocol
My first InsideTracker panel flagged a handful of amber items: suboptimal ferritin, slightly elevated hsCRP, testosterone in range but on the lower end. The platform told me to add magnesium, reconsider protein source, and sleep more. Six months later I retested. The ferritin came up. Inflammation markers improved slightly. Nothing I actually cared about changed.
I switched to Function Health after a friend made the case for it. More biomarkers, cleaner interface, lower cost per panel. I stayed with it for about 10 months. Vitamin D improved meaningfully. Homocysteine came down. Blood pressure kept doing its own thing, and the other symptoms stayed right where they were.
A year in I'd built a detailed personal tracker, correlating markers across time, cross-referencing changes in sleep and training volume with each test, trying to find what was driving what. The data was thorough. The picture it was pointing me toward wasn't something either platform was built to surface.
Both services are built to help you improve individual markers. That's legitimate, and for plenty of people it's useful. The problem is that the pattern extremely common in men past 40, where blood pressure is creeping up, erectile function is declining, and energy has a lower floor, isn't driven by any one marker you can tweak in isolation. It's driven by a mechanism that sits upstream of the panel entirely.
I didn't find that by running more tests. I found it by going back to the primary literature.
The research that changed how I was thinking about this
I'd been through the standard nitric oxide research before. The general forum understanding on ExcelMale is: L-arginine feeds the eNOS pathway, citrulline converts more efficiently, add pycnogenol for endothelial support, see what happens. I'd run that stack for a few months and noticed a modest initial response that didn't hold.
What I hadn't read carefully was a 2015 paper by Nathan Bryan published in Future Science OA. It describes two entirely separate routes for nitric oxide production in the body, and explains why the same supplement stack can produce completely different results in two different men.
Pathway 1, the eNOS route: Your arteries produce nitric oxide through an enzyme called eNOS, which converts L-arginine into NO. This is the pathway nearly every supplement on the market targets. It's also the one that gets blocked by a compound called ADMA, which your body produces naturally and accumulates over time. When ADMA is elevated, L-arginine and citrulline do almost nothing. You're feeding a route that's locked upstream.
Pathway 2, the dietary nitrate route: Dietary nitrates are converted to nitrite and then to nitric oxide through a separate mechanism that doesn't touch eNOS and isn't affected by ADMA at all. Men whose first pathway is compromised can still get meaningful NO production through this second route. High-nitrate plant compounds work here when standard NO supplements don't.
Standard panels don't test ADMA. InsideTracker doesn't test for it. Function Health doesn't either. That's not a failure of those platforms. They weren't designed with this mechanism in mind. But for a specific subset of men, years of data collection can tell you almost nothing about what's actually driving their blood flow problems.
Here's the test: if you've run L-citrulline or arginine and noticed an initial response that didn't hold, that's the pattern. You were feeding the eNOS route while ADMA was blocking it upstream. The supplement arrived at a locked door every time. Shifting toward compounds that support the second pathway — dietary nitrates, glycocalyx-supporting extracts — is where the persistent response comes from. That's the mechanism the standard panels aren't testing for. It's also what the standard supplement stacks aren't targeting.
I rebuilt my protocol around this. Shifted toward compounds targeting the second pathway, adjusted dietary inputs toward high-nitrate sources, ran pycnogenol at a dose informed by the flow-mediated dilation literature rather than a label recommendation. Ninety days, tracking every variable I could measure.
Blood pressure came down. Morning function came back, reliably. Energy had a higher baseline than it had at any point in the previous two years. I shared a variation of the protocol with a few men dealing with similar patterns. Most of them came back with results.
What GRN Labs does and why it's different
GRN Labs starts with a four-minute assessment that takes your existing lab values and current symptoms and produces a vascular age estimate. Vascular age is distinct from your calendar age. A 47-year-old man can have a vascular age of 38 or 58. The difference lives in arterial flexibility, endothelial function, and nitric oxide production capacity, none of which show up on a standard lipid panel or testosterone screen.
If you don't have all the markers yet, GRN Labs can connect you through Quest Diagnostics to run the specific tests that matter for your vascular profile. You don't need to come in with a full panel already in hand.
Based on your vascular age and the specific combination of results, the protocol is built around your individual profile. A pharmacist reviews every supplement recommendation before it reaches you, so the guidance is checked rather than purely algorithmic. Every recommendation follows a citation-first structure: mechanism, published study, dose, product.
The 90-day re-test is built into the subscription. At 90 days, you re-test the same markers. The goal is a number, a before and an after side by side, that confirms the protocol is working for your specific vascular profile. If the markers moved in the right direction, the protocol continues. If they didn't, it adjusts. Either way, the year continues from there.
Side-by-side comparison
| Feature | InsideTracker | Function Health | Empirical Health | GRN Labs |
|---|---|---|---|---|
| Cost | $699+/yr | $499/yr | $190 one-time | $199/yr |
| Runs its own bloodwork | ✓ Yes | ✓ Yes | ✓ Yes | Via Quest if needed |
| Protocol built to your vascular profile | ✗ | ✗ | ✗ | ✓ Yes |
| Vascular age assessment | ✗ | ✗ | ✗ | ✓ Yes |
| Pharmacist oversight on recommendations | ✗ | ✗ | ✗ | ✓ Yes |
| 90-day re-test for verification | ✗ | ✗ | ✗ | ✓ Included |
| Protocol adjusts if markers stall | ✗ | ✗ | ✗ | ✓ Yes |
| Addresses vascular-erectile function link | ✗ | ✗ | ✗ | ✓ Yes |
| Supplement recs with published citations | Partial | Partial | ✗ | ✓ Every recommendation |
- ✗ No vascular age assessment
- ✗ No protocol built to your results
- ✗ No 90-day re-test for verification
- ✗ No vascular age assessment
- ✗ No protocol built to your results
- ✗ No re-test to verify anything changed
- ✗ Cardiac risk score, not vascular age
- ✗ One doctor consult, no ongoing protocol
- ✗ No re-test to verify markers changed
- ✓ Vascular age assessment included
- ✓ Protocol built to your specific profile
- ✓ 90-day re-test verifies the markers moved
What I liked, and where it falls short
Specific to GRN Labs, since that's the part of this review most people are here for.
- Protocol is built around your specific vascular age and health profile
- Addresses the vascular age gap that standard panels miss entirely
- 90-day re-test produces a verified before and after with actual numbers
- $199 per year is less than a single InsideTracker panel
- Pharmacist oversight on every supplement recommendation
- Every recommendation has a mechanism, study, and dose attached
- Can connect you through Quest Diagnostics if you need the right markers run first
- Protocol adjusts based on re-test results, not left static for the year
- Less precise if your most recent lab data is more than 18 months old and you haven't run the Quest Diagnostics panel yet
- Newer product with less long-term outcome data than the major platforms
- If broad metabolic tracking across 100+ markers with trend visualization is the priority, the major platforms serve that better
- A physician relationship is still needed for anything requiring diagnosis or prescription
The honest pushback worth taking seriously
The strongest version of the counterargument goes like this: InsideTracker and Function Health have been around longer, processed substantially more data, and their general recommendations are evidence-based. A newer platform built around a specific vascular mechanism is a bet on that mechanism being the right one for you. That bet isn't guaranteed to pay off.
That's fair. If you're starting from zero and you want a comprehensive baseline, both of the major platforms are genuinely useful starting points.
The problem is that this argument is most relevant for people who haven't already been through the data collection phase. If you've run the panels, followed the recommendations, and still haven't moved the markers that sent you to these services in the first place, a protocol built around your specific vascular profile is the more logical next step than another panel.
Who this is actually for
- You have bloodwork from the past 18 months, or you're ready to run the right markers
- You're dealing with declining erectile function and want to address the vascular root
- Your blood pressure has been creeping up and the standard recommendations haven't moved it
- Your energy or arterial health feels off in ways that your labs haven't explained
- You've tried the standard supplement stack and seen limited or fading response
- You want a protocol with a re-test built in and a clear endpoint for measuring whether it worked
- You're already spending $499 or more per year on tracking and want to know what to do with it
- You want broad metabolic tracking across 100+ markers with longitudinal visualization
- You're looking for something that replaces a physician relationship
- You're early in the process and not yet sure what you're trying to address
- You want a diagnostic service rather than a guided vascular protocol
A few questions worth asking yourself first
These are the questions I wish I'd asked at the start. If most of them land close to home, the protocol is probably worth testing.
- Has your blood pressure been drifting upward since your mid-40s despite making the changes your last lab report recommended?
- Have morning erections become less reliable than they were five years ago, and has your doctor's answer been some version of "that's normal for your age"?
- Have you tried L-arginine, L-citrulline, or a standard nitric oxide product and noticed little to no lasting response?
- Has your energy floor dropped in a way that more sleep and better training haven't fully corrected?
- Do you have lab results from the past 18 months that include inflammation markers, testosterone, and a basic metabolic panel?
- Have you ever looked at a result that came back "in range" and still felt like something was clearly off?
You've done the work. You ran the panels, followed the recommendations, and the markers that sent you to these services are still where they were. The problem was never that you didn't have enough data. It was that no one built a protocol around what the data was pointing at. That's what the assessment is for.
Your panels collected the data. This is where you find out what to do with it.
Four-minute assessment that maps your existing lab values and symptoms to a vascular age estimate. Don't have recent labs yet? The assessment works either way — it tells you exactly which markers to run first. The protocol is built around your specific vascular profile, pharmacist-reviewed, with a 90-day re-test to verify the markers moved.