---
title: "Know Your Numbers | Magellan"
description: "Test → act → retest beats supplement roulette. These are the mail-in numbers with the clearest next step."
url: "https://magellanlongevity.com/guides/tests.md"
canonical: "https://magellanlongevity.com/guides/tests.html"
html: "https://magellanlongevity.com/guides/tests.html"
type: "buyers-guide"
products: 10
citations: 185
updated: 2026-09-02
author: "Gabriel Radu, DO"
author_credentials: "Physiatrist (PM&R). NY medical license 275110. NPI 1376861765."
publisher: "Magellan Longevity"
content_format: "markdown"
---

# Know Your Numbers: The Blood & Age Tests Worth Doing

[Home](https://magellanlongevity.com/) › Buyer's guides › Know Your Numbers

**HTML version:** https://magellanlongevity.com/guides/tests.html · **In the Magellan app:** https://magellanlongevity.com/#/guides/tests

*Test → act → retest beats supplement roulette. These are the mail-in numbers with the clearest next step.*

## Why this guide is ordered the way it is

The highest-value habit on this entire site costs less than most supplement stacks: measure something meaningful, change one thing, measure again. This guide ranks the at-home panels by how clear the "act on it" step is — each card links the monograph and the studies behind it. Results are education, not diagnosis; bring them to your clinician.

## The cardiovascular pair most panels skip

ApoB counts the particles that drive atherosclerotic risk, and Lp(a) is the once-in-a-lifetime check that reclassifies risk for millions who’ve never heard of it.

| Pick | Evidence grade | Citations | Typical price | Why it is here |
| --- | --- | --- | --- | --- |
| [ApoB Home Test Kit](https://magellanlongevity.com/p/140.md) | Measurement tool | 18 | $79.00 | Large Mendelian randomization studies, prospective cohorts and meta-analyses — in one pooling of 233,455… |
| [Lp(a) Mail-In Test](https://magellanlongevity.com/p/141.md) | Measurement tool | 19 | $152.00 | Large meta-analyses, prospective cohorts, and Mendelian randomization studies establish elevated Lp(a) as a… |

## The metabolic & inflammatory background

Fasting insulin catches metabolic drift years before glucose moves; hs-CRP reads the inflammatory background these interventions are trying to lower.

| Pick | Evidence grade | Citations | Typical price | Why it is here |
| --- | --- | --- | --- | --- |
| [Fasting Insulin / HOMA-IR Kit](https://magellanlongevity.com/p/145.md) | Measurement tool | 16 | $79.99 | Higher fasting insulin and HOMA-IR reflect greater insulin resistance, a central feature of metabolic… |
| [hs-CRP Inflammation Test](https://magellanlongevity.com/p/142.md) | Measurement tool | 19 | $99.00 | Across large prospective cohorts and meta-analyses, higher hs-CRP is consistently associated with increased… |

## Organ-level early warnings

Cystatin C tracks kidney function without the muscle-mass distortion of creatinine; GGT and ferritin flag liver load and iron status — all actionable, all cheap.

| Pick | Evidence grade | Citations | Typical price | Why it is here |
| --- | --- | --- | --- | --- |
| [Cystatin C / eGFR Kidney Test](https://magellanlongevity.com/p/157.md) | Measurement tool | 18 | $55.00 | Across large cohorts and meta-analyses, cystatin C-based eGFR is at least as accurate as creatinine-based… |
| [GGT Liver-Health Test](https://magellanlongevity.com/p/156.md) | Measurement tool | 22 | $40.00 | Large prospective cohorts and meta-analyses consistently link higher serum GGT, even within the reference… |
| [Ferritin / Iron-Status Test](https://magellanlongevity.com/p/147.md) | Measurement tool | 18 | $99.00 | Iron status has a U-shaped relationship with health: iron deficiency (low ferritin) is a leading cause of… |

## Function, fats & stress

Grip strength is the classic bedside marker of aging trajectory. The Omega-3 Index measures what your fish-oil habit actually achieved. Cortisol curves need careful interpretation — read the monograph first.

| Pick | Evidence grade | Citations | Typical price | Why it is here |
| --- | --- | --- | --- | --- |
| [Grip-Strength Dynamometer](https://magellanlongevity.com/p/153.md) | Measurement tool | 16 | $45.00 | Across large prospective cohorts and meta-analyses, lower grip strength is consistently associated with… |
| [Omega-3 Index Test](https://magellanlongevity.com/p/143.md) | Measurement tool | 22 | $54.95 | In prospective cohort studies and pooled analyses spanning dozens of cohorts, higher blood levels of EPA +… |
| [Saliva Cortisol Stress Test](https://magellanlongevity.com/p/149.md) | Preliminary | 17 | $129.95 | Across large studies, dysregulated cortisol patterns track with worse health: a meta-analysis found flatter… |

## What the studies actually used

The dose ranges below are the ones the cited human trials used — a description of the evidence, not a recommendation. Talk to your physician before acting on any of them.

| Compound or device | Evidence grade | Dose used in studies |
| --- | --- | --- |
| ApoB Home Test Kit | Measurement tool | Once to find out where you stand, then repeat about 8-12 weeks after any deliberate change - a statin, a real diet change, meaningful weight loss. Fasting is not required for ApoB. Stick to one lab, because between-lab differences are larger than the changes you are looking for. |
| Lp(a) Mail-In Test | Measurement tool | Once in adult life. Lp(a) is set by the LPA gene you were born with and moves very little afterwards, so one good result is the result. Repeat only if the units or the lab change and you cannot line the numbers up. |
| Fasting Insulin / HOMA-IR Kit | Measurement tool | Fasting 10-12 hours, and only ever compared against your own previous result from the same laboratory. Twice a year at most. Treat the trend as the signal and ignore the absolute HOMA-IR figure printed on the report. |
| hs-CRP Inflammation Test | Measurement tool | Only when you are well. Check it twice, a couple of weeks apart, and take the lower value - a single high reading is far more likely to be a cold than a signal. Do not test within 2-3 weeks of any infection, injury, vaccination or hard unaccustomed exercise. |
| Cystatin C / eGFR Kidney Test | Measurement tool | Not a routine self-monitoring test. Reasonable once if you have a specific reason to think a creatinine-based eGFR is misleading you - unusually high or low muscle mass, or a creatinine result you are trying to make sense of. Otherwise this belongs to whoever is already following your kidney function. |
| GGT Liver-Health Test | Measurement tool | Not a tracking test. Reasonable once if you have a concrete reason - regular alcohol intake you want an objective read on, a medication known to affect the liver, or a metabolic picture you are already working on. Interpreting it in isolation is the mistake. |
| Ferritin / Iron-Status Test | Measurement tool | Reasonable once if you have a specific reason - heavy periods, a plant-based diet, blood donation, unexplained fatigue - and again 3 months after starting iron, no sooner. Not a number to track routinely if you have no reason to suspect a problem. |
| Grip-Strength Dynamometer | Measurement tool | Three squeezes per hand, seated, elbow at 90 degrees, best value recorded - and the same chair, same arm position, same time of day every time. Monthly is plenty. What matters is your own trend over years, not where you sit against a population chart. |
| Omega-3 Index Test | Measurement tool | Once to find your baseline, then again about 4 months after changing oily fish intake or starting a supplement - red cell fatty acids turn over slowly and anything sooner is reading noise. Most people sit around 4-5%; the level associated with lowest risk in the cohort work is roughly 8% or above. |

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## Related on Magellan Longevity

- [Wearables & Home Vitals](https://magellanlongevity.com/guides/wearables.md)
- [Home Water, Filtered](https://magellanlongevity.com/guides/water.md)
- [Light, Heat & Recovery Tech](https://magellanlongevity.com/guides/recovery.md)
- [The Longevity Gift Guide](https://magellanlongevity.com/guides/gifts.md)
- [Evidence-based longevity supplements](https://magellanlongevity.com/longevity-supplements.md)
- [Longevity research map](https://magellanlongevity.com/longevity-research-map.html)

## Scope and disclosures

Educational information, not medical advice. Nothing here is intended to diagnose, treat, cure, or prevent any disease. Talk to your physician before starting any supplement or device, especially if you are pregnant, nursing, or taking medication.

Editorial firewall: evidence grades are assigned from the published research and are independent of any affiliate commission. As an Amazon Associate, Magellan Longevity earns from qualifying purchases.

Reviewed for accuracy by a board-certified physician (DO).