Five things your wearable can't tell you

A ring or a band is very good at one job: watching you from the outside. Almost everything it reports is inferred from three signals — movement, skin temperature and pulse. Here is what sits outside that, and why it takes blood to see it.

One
Whether you have enough iron stored

Tiredness is what people take to a sleep score, and a sleep score has no way to answer it. Ferritin is the marker that reflects stored iron, and it is one of the most commonly low results in the general population. No wearable measures it, and no amount of sleep data implies it.

Two
What your thyroid is doing

Thyroid hormones set your metabolic tempo — which is exactly the thing people try to read out of resting heart rate and recovery scores. TSH, FT3 and FT4 are blood measurements. There is no wrist-based proxy for them.

Three
Whether there is background inflammation

High-sensitivity CRP is a general marker of inflammation. It matters on its own, and it also changes how other results should be read — which is the point most panels skip. More on that below.

Four
Your vitamin D and B12 status

Both are common shortfalls, both are invisible to any device on your wrist, and both are cheap and easy to measure from a very small volume of blood.

Five
Which of your numbers can even be trusted

This is the one nobody puts on a marketing page, and it is the most useful thing on this list.

Ferritin is not only an iron marker. It also rises with inflammation. So a ferritin result on its own can read comfortably high while iron stores are actually fine, low, or somewhere you'd never guess — because inflammation lifted the number for an unrelated reason.

What a baseline panel actually contains

Four markers: vitamin D, ferritin, vitamin B12, and hs-CRP. That is the whole entry panel — three things people are commonly short of, plus the one that makes the others readable. It fits comfortably inside a single small home sample.

Your wearable keeps doing what it is good at. The panel covers the half it cannot see, and peppies puts both on one timeline so you are comparing them against each other rather than against nothing.