Question 1

How do I read my lab results?

Accepted Answer

Lab results show your measured value alongside a reference range (e.g., 3.5-5.0 mEq/L). Values outside this range are flagged as High (H) or Low (L). Reference ranges are based on 95% of healthy adults - 5% of healthy people will have values outside the normal range. Context matters more than any single value.

Question 2

What does "within normal limits" mean?

Accepted Answer

"Within normal limits" (WNL) means your result falls within the reference range established by the laboratory. This is reassuring but does not guarantee absence of disease. Reference ranges are statistical, not absolute - your doctor interprets results in the context of your symptoms, history, and other tests.

Question 3

Should I be worried about borderline results?

Accepted Answer

Borderline results (slightly outside reference range) require clinical context. A slightly elevated result in an asymptomatic person with no risk factors may just need monitoring. In someone with relevant symptoms or risk factors, even borderline results may prompt further testing. Always discuss with your doctor.

Question 4

Why do lab reference ranges differ between labs?

Accepted Answer

Reference ranges are laboratory-specific, based on the equipment and methodology used, as well as the demographic of the local reference population. Always use the reference range printed on your own lab report, not values found online or in a different laboratory's report.

Question 5

What is the difference between CBC and CMP?

Accepted Answer

CBC (Complete Blood Count) measures blood cell types and counts. CMP (Comprehensive Metabolic Panel) includes BMP tests (kidney function, electrolytes, glucose) plus liver function tests. BMP (Basic Metabolic Panel) is a subset of CMP without liver tests. Your doctor orders the panel most relevant to your clinical situation.

Question 6

Do I need to fast before blood tests?

Accepted Answer

Fasting (8-12 hours, water only) is required for: fasting glucose, fasting lipid panel (especially triglycerides), and some other metabolic tests. It is not required for: CBC, thyroid tests (TSH, T4), HbA1c, most kidney and liver tests. Your lab requisition will specify fasting requirements.

Lab Result Interpreter

Complete Blood Count (CBC)

Want to understand your full health picture?

References

Frequently Asked Questions

Related Tools

HbA1c Converter

Cholesterol Ratio Calculator

eGFR Calculator

Complete Blood Count (CBC)