Reading a client's blood work over years, not one panel at a time

One panel tells you where a client stood on the day of the draw. Years of panels tell you which way they're moving, and a slow drift can stay inside the lab's range at every single draw while it heads somewhere you'd want to know about. To read a series fairly, put the results in date order, group them by lab and unit, and keep notes that explain each draw, so a new lab or an afternoon appointment isn't mistaken for a change in the client.

I build Sera, a lab-review workspace for practitioners, so read the last section with that in mind. Everything before it works with any record you keep.

If your question is about one change, such as a new supplement and the retest after it, Did it work? Reading a marker before and after a change covers that. This article is about the slower question: where has this client been heading over the last five years?

What a single panel can't show

Each report is read against its own reference interval. A result inside it gets no flag, and a report with no flags gets filed. That's reasonable for one report. Over years it means a gradual change can go unnoticed, because no single result ever crosses a line.

Here is how that can look. These are illustrative numbers, not a real client:

Every value in that table sits inside the guideline lines described below. Read across the rows, all three markers have moved the same way for five years. That isn't a diagnosis. It's a question worth asking, and you can only ask it when the results sit next to each other.

Three slow drifts and what to know about each

TSH creeping up. The TSH range page gives the traditional reference range as 0.5 to 4.5 mIU/L, as the American Thyroid Association describes it. Laboratories print their own limits, from about 0.3 to 0.45 at the bottom and 4.2 to 5.3 at the top, so a TSH that climbs over several years can be flagged at one lab and printed as normal at another. TSH also runs highest overnight and in the early morning, so part of the movement in a series can be the time of the draw. Thyroid series have their own guide: Reading thyroid labs over time.

HbA1c edging higher. The ADA starts its prediabetes range at 5.7% (39 mmol/mol). NICE in the UK and Diabetes Canada draw the line higher, at 6.0% (42 mmol/mol). A client at 5.8% can be in the prediabetes range on one country's definition and not on another's, so note which definition a report uses. MedlinePlus explains that HbA1c reflects average blood glucose over the past two to three months, so each result in a yearly series is already an average, not a snapshot of one morning. The figures and sources are on the HbA1c range page.

Ferritin falling. The American Society of Hematology's 2026 guideline diagnoses iron deficiency in adults at a ferritin of 30 ng/mL or lower, and uses 50 for higher-risk groups such as people with heavy menstrual bleeding. A ferritin that falls from 95 to 33 over five years has stayed above both the WHO line of 15 and the ASH line of 30 at every draw. Ferritin is also an acute-phase protein: inflammation raises it independently of iron stores. One draw taken during an illness can sit above the trend and make a steady fall look as if it reversed. The ferritin range page has the sources, and Why one marker rarely tells the story goes through reading ferritin with the rest of the iron panel.

Lining up results from different labs

Years of results usually means more than one lab. Before you read a direction into them, line them up so you're comparing like with like.

• Order by draw date, not by the date the report was issued.
• Keep the unit exactly as printed. Some unit differences are only names: ferritin in ng/mL and µg/L is the same number. Others are different scales. HbA1c can be reported in % or in mmol/mol, and 5.7% and 39 mmol/mol are the same result and can't share an axis without converting.
• Read each value against its own lab's interval. A step up in the year the client changed labs may belong to the lab, not the client.
• Look within one lab first. A drift that shows up inside one lab's results is more convincing than one that only appears across a change of lab.
• Check the conditions matched. Time of day matters for TSH, and a draw a week after a cold can raise ferritin. The guide on reading a marker before and after a change lists the conditions to keep the same.

What to write down so a change can be explained later

In five years nobody will remember why the 2023 result looked odd. The notes you write at the time are what let you explain it. Next to each draw, record:

The last row is easy to skip. A year with no results is worth marking, so that a chart doesn't draw a smooth line through a year nobody measured.

Reading the series

1. Look at the direction across three or more draws before reading much into the latest one.
2. Compare the latest result with the client's own earlier results, not only with the range.
3. Read related markers together. The ferritin note says to read ferritin alongside transferrin saturation and an inflammatory marker, and TSH reads better next to free T4 from the same draw.
4. Mark when anything changed, so you can see what came before and after it.
5. When a drift crosses a guideline line, or keeps heading toward one, take it to the client's doctor. A trend is a reason to look closer or refer, not a conclusion.

If a step in the series lines up with a change of lab, a different time of day or a draw taken while unwell, the fair reading is that you don't know yet. The next draw under matched conditions will tell you more.

Where Sera fits

Sera puts each client's results on one timeline across years and labs, against optimal and sufficient bands whose sources and evidence grades are published. You can put up to three markers on one chart, so TSH, HbA1c and ferritin from the example above could be read together. Diet, supplement and medication changes are marked on the trend charts. Every result stays in the unit the lab reported, and Sera flags a marker that arrives in more than one unit. It doesn't convert units, so a % and a mmol/mol HbA1c stay visibly different. Sera also points out recognized patterns across markers, such as Subclinical Hypothyroidism or Blood Sugar in the Prediabetes Range, and suggests a retest date for any result out of range, plus a yearly one for the markers on a typical annual check-up list. It doesn't diagnose or recommend treatment.

It's free for three clients with no card, and new accounts come with two example clients to explore. There's a 3-minute tour if you'd rather watch first.

Alina Radu is the founder of Sera and a software engineer. The idea started with her own Hashimoto's tests, scattered across years without the big picture.