How to read your lab report

By the SECURECORDS team · October 5, 2026 · 7 min read

Results, units, reference ranges and H/L flags explained in plain language — and why a result outside the range isn't automatically a problem.

A lab report can look like a wall of abbreviations and numbers. Most reports, from any lab in any country, are built the same way, though. Once you know the parts, it becomes much easier to read — and to have a useful conversation about it with your health professional.

The parts of a lab report

Each test usually takes one row, with these columns:

Test name

What was measured — often abbreviated: HbA1c, ALT, TSH, eGFR. Different labs use different names for the same test ("Hemoglobin A1c", "Glycated hemoglobin" and "HbA1c" are all the same thing).

Result

Your value. Sometimes it's written as < 0.6 or > 90, which means the true value is below or above what the test reports precisely.

Units

How the result is expressed — for example mmol/L or mg/dL. The same test can be reported in different units in different countries, so the number only makes sense together with its unit. Our guide mmol/L or mg/dL? explains this.

Reference range

The span of values the lab considers typical, such as 3.6–6.0. More on this below — it's the most misunderstood column.

Flag

A marker when the result falls outside the reference range: H (high), L (low), an asterisk, or bold text. Some labs also flag results that need urgent attention.

Around the table you'll also find the collection date (when the blood was drawn — the date that matters for tracking), the date it was reported, and notes such as whether you were fasting.

What a reference range actually is

A reference range is not a line between "healthy" and "sick". Most labs set it by testing a large group of healthy people and taking the middle 95% of their results. That has two consequences that surprise many people:

• About 1 in 20 healthy people will have any given result slightly outside the range, simply because of how the range is defined.
• The more tests on a report, the more likely it is that one is flagged, even when nothing is wrong. With 20 tests, a flag or two is common.

The opposite also holds: a result inside the range doesn't guarantee anything on its own. That's why a single flag is a starting point for a conversation, not a conclusion — and why your health professional looks at the whole picture.

Why ranges differ between labs

Two labs can print different ranges for the same test. Labs use different instruments and methods, test different reference groups, and some ranges differ by age or sex. That's why it's best to compare a result with the range printed on your own report, rather than with a number from the internet.

It also matters when you compare results over time: if you switch labs, a small change may come from the method rather than from you.

Things that can affect a result

Many results naturally vary from day to day. Common reasons include:

• Fasting or not — glucose and triglycerides in particular.
• Time of day — some hormones follow a daily rhythm.
• Recent illness or hard exercise — inflammation markers and some enzymes can rise temporarily.
• Hydration, medications and supplements.
• Normal biological and measurement variation — two draws a week apart are rarely identical.

This is one reason a single result tells you less than a series of results over time.

Reading a report, step by step

1. Check the collection date and whether the report notes fasting.
2. For each result, read the value together with its unit.
3. Compare it with the reference range on the same report, and note any flags.
4. Look at how it compares with your earlier results — the trend is often more informative than the single number.
5. Write down your questions for your health professional.

How SECURECORDS helps

SECURECORDS keeps every result from every report in one place, shows each value against a reference range (standard clinical reference ranges by default, or the range from your own lab), and charts how it changes over time. You can import the PDF from your lab instead of typing — it's read on your device, and you check every value before it's saved. And everything is end-to-end encrypted, so we can't read any of it.

It doesn't interpret your results or give advice — that's a conversation for you and your health professional, and having all your numbers in one place makes it a better one.