How to read a lab report
Five steps turn a page of numbers into questions you can ask. The example below is fictional.
Fictional example. Not a real person or laboratory.
Example Regional Laboratory
Sample Patient · Collected 08:10 · Fasting: yes (reported)
| Test | Result | Unit | Reference interval | Step |
|---|---|---|---|---|
| Glucose, fasting | 92 | mg/dL | 70–99 | 1 · 2 · 3 |
| Hemoglobin A1c | 5.4 | % | 4.0–5.6 | 1 · 2 · 3 |
| IGF-1 | 168 | ng/mL | Interval for age and sex printed here | 1 · 3 |
- Annotation 1: Exact test name as printed. “Glucose, fasting” is not the same test as a random glucose.
- Annotation 2: Result and unit belong together. Intervals differ between laboratories and methods.
- Annotation 3: Use the interval on this report, then check the collection line for date, time and fasting.
All values on this sample are invented to show how to read a report. They are not reference values or targets.
The five steps
1.Find the exact test.
Glucose can appear on a chemistry panel, a fasting test, or a test taken at another time. Record the name as printed.
2.Keep the result and unit together.
A glucose result in mg/dL and one in mmol/L use different scales. Before comparing, confirm the units and what was measured.
3.Use the reference interval on that report.
An H or L mark usually means the result is above or below the laboratory's comparison interval. A result inside the interval can still need attention in context, and a mark alone does not establish a diagnosis.
4.Check collection details.
Note the date, time, laboratory, and fasting status when relevant. Recent illness, medication changes, and testing methods can matter.
5.Ask what decision the result informs.
Is it helping explain symptoms, screen for a condition, establish a baseline, or monitor treatment? The same test can serve different purposes.
Three words that sound alike
| Term | What it means |
|---|---|
| Reference interval | The laboratory's comparison range, which can vary by method and reference population. |
| Clinical decision threshold | A point used by a guideline for a defined decision under specified conditions. |
| Treatment target | A goal selected for a person or a defined group receiving care. |
This page does not list target values. A reference interval is not a treatment goal, and a guideline threshold applies to a defined decision.
Comparing results
Start with the same test, units, and lab where possible. Compare collection conditions and ask whether the change fits related results and how you have been feeling. Ask whether the difference is large enough to affect the next decision.
Sources and review status
- How to understand your lab test results · MedlinePlus, National Library of Medicine · Last updated September 4, 2025
- The MedlinePlus page covers reference ranges, differences between laboratories, units, and results inside or outside a range. The explanations of an H or L mark, a clinical decision threshold and a treatment target are Foundation explanatory text pending clinical review.
General education only. Bring your report, symptoms, and medication list to a qualified healthcare professional for advice about your care. Follow instructions from your lab or clinician if a result is marked critical.