Signal categories

The signals in Lab can be grouped in two complementary ways. The chart's Group toggle lets you switch between them — "Biological System" for the body-systems view, "Kind" for what kind of measurement each signal is.

Biological system

The classic split — what part of the body the signal lives in. Use this when you're thinking about a physiological system as a whole.

System	Examples
Nervous / neurochemical	Dopamine, serotonin, GABA, acetylcholine, norepinephrine
Endocrine / hormonal	Cortisol, testosterone, estrogen, growth hormone, IGF-1, thyroid
Circadian	Melatonin, adenosine pressure, orexin, histamine
Metabolic	Glucose, insulin, glucagon, leptin, GLP-1, ketone, burn rate
Cardiovascular	HRV, blood pressure, vagal tone, nitric oxide
Organ health	ALT, AST, eGFR, creatinine, hsCRP, bilirubin, albumin
Hematology	Hemoglobin, hematocrit, platelets, WBC
Nutritional	Vitamin D, B12, ferritin, magnesium, zinc, omega-3 index

Kind — what type of measurement is it

The second axis tells you what the value is, mathematically and clinically. Useful when you want to compare apples to apples — say, "show me every concentration I can verify with a lab test," or "show me the felt-experience meters."

Kind	What it is	Examples
Analyte	A chemical concentration measurable in blood or tissue	Cortisol, glucose, IGF-1, vitamin D, BDNF
Drug concentration	Plasma level of something you took (PK curve)	Caffeine plasma, retatrutide plasma
Vital sign	A directly-observable physical signal	HRV, blood pressure, body temp, SpO2
Body composition	Slow anthropometric measure	Weight, fat mass, lean mass
Flux	A rate — mass or energy flowing through a pathway	Calorie burn rate, fat oxidation rate, gastric emptying
Activity	A dimensionless multiplier on a biological process (1.0 = baseline)	CYP3A4 activity, mTOR signaling, insulin sensitivity
Pool	An accumulated reservoir	Liver glycogen, muscle glycogen, sleep debt
Index	A composite weighted score	Strength readiness, neuroplasticity score, eGFR
Subjective (PRO)	Felt-experience meter — patient-reported	Energy, focus, mood, calm, sleep pressure

Why this matters for reading the chart

The two axes mean different things for what you do with a signal:

• Biological system answers what part of the body is responsible?
• Kind answers what does this number actually mean and how do I verify it?

For example: cortisol is type: hormone and kind: analyte. The hormone label tells you it's an endocrine signal driven by the HPA axis. The analyte label tells you it's a chemical concentration, has a reference range, and you can order a blood test for it.

Each signal also carries:

• Measurability — how you'd obtain the value yourself: lab, cgm, wearable, self-report, anthropometric, or modeled-only. The "Order labs for this" affordance in the inspector keys off this.
• Timescale — how fast it meaningfully changes: seconds, minutes, hours, days, weeks, months. Drives the default chart zoom so vitamin D defaults to a multi-week view while cortisol defaults to a day.