Biomarkers · Updated January 2027
A January reset is a good excuse to test something instead of just resolving to. ApoB, HbA1c, hs-CRP and vitamin D are the four measurements with the strongest evidence behind them — and the ones most annual physicals still skip or get wrong.
The one-line answer: test ApoB, HbA1c, hs-CRP and vitamin D once now as your 2027 baseline, retest in 8–12 weeks after any change you make, and skip the 40-plus-marker “longevity panels” until you've acted on these four.
A resolution without a number attached to it is a mood, not a plan. The at-home testing category has matured enough since 2024 that a capillary fingerstick or dried-blood-spot sample, mailed to a CLIA-certified lab, can now return several genuinely useful markers without a phlebotomy appointment. We cover the accuracy tradeoffs between at-home kits and a full venous lab panel in a dedicated guide — read that first if the methodology, not the markers, is what you're trying to evaluate. This page is about which four numbers are worth testing for a January reset, and which of the bigger “longevity panels” are still mostly noise for someone just getting started.
Standard lipid panels estimate LDL cholesterol content rather than counting the actual number of atherogenic lipoprotein particles circulating in the blood. Apolipoprotein B (ApoB) counts particles directly, and a meaningful fraction of adults show “discordance” — a normal-looking LDL-C alongside an elevated ApoB — particularly when triglycerides or insulin resistance are also elevated. Several major cardiology guidelines now list ApoB as an optional or preferred refinement to standard risk scoring for exactly this reason. Not every at-home kit offers it yet, so check the panel contents before ordering rather than assuming it's bundled with a standard lipid test.
HbA1c reflects roughly three months of average blood glucose rather than a single fasting number, which makes it a better-matched measure for catching a slow metabolic drift than an annual fasting glucose check. Testing every January builds a personal trend line: a value moving from 5.3% to 5.6% over consecutive years is more actionable than either number alone, even though both technically fall in the “normal” range. Certain anemias and hemoglobin variants can skew HbA1c independent of actual glucose control, so a single unexpected result is worth confirming rather than treated as final.
High-sensitivity C-reactive protein (hs-CRP) is inexpensive to test and has a real evidence base behind it — trial data going back to the JUPITER study era found that people with elevated hs-CRP despite otherwise unremarkable LDL-C benefited from statin therapy, which is part of why hs-CRP is now used as a refinement to cardiovascular risk scores rather than a stand-alone diagnosis. The practical catch: acute infection, injury or even a hard workout in the prior 24 hours can spike CRP non-specifically. A single elevated reading is a reason to retest in 2–3 weeks, not a reason to panic.
Dried-blood-spot vitamin D kits correlate reasonably well with a venous serum 25(OH)D lab draw — better than most other markers on this page transfer to a fingerstick format — which makes vitamin D the one place an at-home test is close to as good as the lab version. Deficiency is common in winter at most temperate latitudes simply because UVB synthesis drops sharply, so a January test catches people at their annual low point rather than their summer peak. If your number comes back low, our dedicated vitamin D3+K2 guide covers dosing and why the two nutrients are usually paired.
Several of the more elaborate “full longevity panel” products test 30–50 markers in one draw, and a meaningful share of them have poor test-retest reliability or simply don't change what you'd do differently. Testing more markers than you have a plan to act on mostly buys statistical noise: with enough markers tested, something will land outside the reference range by chance alone, without a clear next step attached. The four markers above are the ones with a defined action if they come back abnormal — that's the actual bar for whether a test earns a spot in a January baseline panel.
| Biomarker | What It Catches | At-Home Accuracy | Retest Interval |
|---|---|---|---|
| ApoB | Atherogenic particle count, beyond LDL-C | Good, on kits that include it | Annually, or 8-12 weeks after a lipid-focused change |
| HbA1c | 3-month average blood glucose | Good; some hemoglobin variants can skew it | Annually, or 8-12 weeks after a diet change |
| hs-CRP | Non-specific inflammation, CV risk refinement | Moderate; sensitive to recent illness/injury | Retest in 2-3 weeks if elevated, otherwise annually |
| Vitamin D (25-OH-D) | Deficiency, especially in winter | Best of the four for at-home dried-blood-spot | Annually, or 8-12 weeks after starting supplementation |
The kit should name the actual accredited lab processing your sample, not just a brand name on the box.
Look for a numeric result and reference range, not just a vague “normal/high” bucket with no value attached.
3-7 business days is typical; a listing that won't state a turnaround time is a minor red flag.
ApoB and glucose-adjacent markers have different fasting requirements; the kit should tell you which applies before you order.
ApoB and HbA1c first since they carry the clearest action, then hs-CRP and vitamin D to round out the picture.
Prioritize a kit that explicitly lists ApoB in the panel contents rather than assuming it's bundled with a standard lipid test, and confirm the processing lab is CLIA-certified.
View on AmazonA once-a-year HbA1c builds a trend line that a single fasting glucose reading can't; retest at the same time each January for the most useful comparison.
View on AmazonCheap and genuinely useful as a refinement to cardiovascular risk, but treat one elevated reading as a prompt to retest in a few weeks rather than a diagnosis on its own.
View on AmazonThe dried-blood-spot method correlates well with a lab venous draw for this specific marker, making it the highest-confidence at-home test on this list.
View on AmazonMost kits recommend a 9-12 hour fast for triglyceride-adjacent markers, though ApoB itself is less fasting-dependent than triglycerides specifically. Follow the instructions that ship with your particular kit rather than a generic rule.
Dried-blood-spot methods correlate well with lab values for HbA1c and vitamin D. hs-CRP and ApoB show more kit-to-kit variability, so choosing a kit that discloses its CLIA-certified processing lab is a more meaningful quality signal here than in many categories.
Not as a starting point for most people. Testing far more markers than you have a plan to act on mostly increases the odds that something lands outside the reference range by chance, with no clear next step attached. The four markers here each have a defined action if abnormal.
Annually is enough for these four markers in someone without an existing diagnosis. Retest 8-12 weeks after a genuine lifestyle change (new diet, new supplement, new training block) to see whether it moved the number.
Retest in 2-3 weeks first, since recent illness, injury or even a hard workout can transiently elevate it. A persistently elevated result is worth discussing with a physician alongside your lipid numbers.
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