How to read a biomarker trend chart in HealthLab

A single lab result is a snapshot on one date: a value that sits inside or outside a reference range. A trend chart is several of those snapshots lined up, and that’s what actually shows direction — whether a marker is climbing slowly, dropping steadily, or just wobbling around one level. HealthLab builds this chart automatically for any biomarker as soon as it has two or more saved results.

This article covers reading the chart itself: where it lives in the app, what the band around the line means, how to change the time period, and where the free view ends and the Pro features begin. What a specific value actually means is a separate question, answered in how to read your lab results.

What to do and where

Step 1. Open a biomarker’s trend chart

In “Lab results,” pick any marker that has been tested more than once — ferritin or fasting glucose, for instance. Instead of a single number, a chart opens: each dot is one result on its own date, and a line connects them in chronological order.

Step 2. Read the reference band around the line

Alongside the line of values, the chart shows a band for that marker’s reference range. Dots inside the band sit within the lab’s normal range; dots above or below it sit outside it. This is the same reference range printed on a paper report, just carried over onto a chart — which is why it varies by lab, age group and sex the same way it does on paper, as explained in how to read your lab results.

Step 3. Change the time period

A period control sits above the chart — switch it to widen the window, from the last few results to the marker’s entire history across years. This matters most when testing has been irregular: a short period might show only one or two jumps, while a longer one immediately reveals whether that’s a one-off blip or a sustained pattern.

Step 4. Check the multi-biomarker trend correlation (Pro)

Pro subscribers get a separate AI feature: multi-biomarker trend correlation. It analyzes the trajectory of several markers at once and surfaces relationships between them over time, rather than simply drawing them side by side on one chart. For example, it can point out that a rise in one marker in your history tends to line up with a drop in another over the same months.

Step 5. Personalized norms on the chart (Pro)

Another Pro feature, personalized norms, adjusts reference ranges for age, sex and pregnancy instead of showing one generic adult range. Values on the trend chart are compared against those adjusted ranges, so a dot that looked borderline against the generic range can land squarely inside the range adjusted for your profile — or the other way around.

Step 6. Export the trend chart for a doctor

Any analysis or trend chart can be exported as a clean PDF straight from the app — generated locally on your device, nothing uploaded to any cloud. That’s a faster thing to hand a doctor than scrolling through each individual result on your phone. For more on preparing that file, see PDF export of lab results for your doctor.

Example: an eighteen-month ferritin trend

Picture four ferritin results saved in HealthLab a few months apart: 14 ng/mL in January 2025, 22 ng/mL in June 2025, 45 ng/mL in January 2026, and 68 ng/mL in June 2026. Each result on its own is just a number on a date. The line on the chart shows something different: a steady climb across the whole period, not a one-time jump.

Look at only the last two results and the chart shows a rise from 45 to 68 — noticeable, but with no context around it. Widen the period to all four dots and the fuller picture appears: the value started below the reference band typical for women of reproductive age and gradually moved inside it. The long view is what answers “is this a trend or a fluke” — the short view can’t answer that question at all. For what the ferritin numbers themselves mean, see ferritin levels.

Edge cases

• Only one result saved. There’s no trend chart yet — the line appears only once a marker has two or more saved results to compare.
• Results came from different labs. The reference band on the chart follows the range attached to each individual result; when labs differ, read the direction of the line first rather than comparing raw numbers across distant dates.
• Gaps between results are very uneven. The chart plots every dot on its own date regardless — a long gap between two results just shows up as a long stretch of line between them, with no hidden data in between.
• The marker isn’t in the app yet. It needs to be saved at least once first — manually, or through AI import from a PDF or photo — before any chart can appear.

None of these situations change data already saved — they’re about how the chart displays it at a given moment, not the underlying history.

What it costs: Free and Pro

The trend chart itself, the reference band around it, the period control, and PDF export of the chart are all available for free, with no limit on how many biomarkers or how many years of history. What’s paid is two AI features layered on top: multi-biomarker trend correlation (Pro) and personalized norms (Pro), which redraw the reference band for age, sex and pregnancy.

That matches how the rest of the app is priced: the basic ability to see a marker’s direction over time is free forever, and the paid tier is specifically the AI layered on top of it — the same split as unlimited manual biomarker entry against the limited free AI imports.

What the chart is — and isn’t — telling you

HealthLab is a tool for storing and viewing lab results, as well as planning medication intake and reminders. The app is not a medical device and does not provide medical advice, diagnoses, or treatment recommendations. A trend chart shows the direction a marker is moving — it doesn’t replace a conversation with a doctor, especially when the line crosses outside the reference band or a marker keeps worsening across several results in a row.

Frequently asked questions

HealthLab: from a dot to a trend

HealthLab turns every saved result into a dot on a chart, and several dots into a visible trend — rising, falling, or holding steady against the lab’s reference band. The same chart works the same way whether it’s tracking one marker or any of the dozens saved in the app.

Getting a value onto the chart in the first place means saving it — manually, or through AI import from a PDF or photo; understanding what the value itself means, beyond the direction of the line, is covered in how to read your lab results and marker-specific guides like ferritin levels or HbA1c levels.

The full list of markers HealthLab builds trend charts for is on the lab results page.