Blood test results, explained

These pages explain what common blood tests measure, what typical adult results look like, and what can make a number higher or lower. They are written for people who have just received a lab report and want to understand it before talking to their doctor.

Reference ranges vary between labs, between men and women, and with age and pregnancy. Always use the range printed on your own report, and treat the ranges here as a general guide.

The six tests

• CBC (complete blood count): Counts your red cells, white cells and platelets and measures hemoglobin, to check general health and look into tiredness, infections or bruising.
• CMP (comprehensive metabolic panel): Measures glucose, electrolytes, and kidney and liver markers, as a broad check of how your body's chemistry is working.
• Lipid panel (cholesterol): Measures total cholesterol, LDL, HDL and triglycerides, which doctors use to estimate heart disease and stroke risk.
• HbA1c: Shows your average blood sugar over about three months, and is used to help identify prediabetes and type 2 diabetes and to monitor diabetes.
• Thyroid tests (TSH, free T4, free T3): Checks TSH and thyroid hormones to see whether the thyroid is underactive or overactive.
• Ferritin and iron studies: Shows how much iron you have stored and available, to look into anemia and iron deficiency.

How to read a lab report

1. Find the reference range column

   Each result is printed next to the range that the lab considers typical for adults like you. Some reports list separate ranges for men and women.

2. Check the units

   The same test can be reported in different units, such as mg/dL or mmol/L for glucose and cholesterol. A number only makes sense next to its unit.

3. Look at the flags

   Labs often mark values with H for high or L for low, or with an asterisk. A flag means the value sits outside the lab's range. It does not tell you whether it matters.

4. Compare with your previous results

   A value that has been stable for years can mean something different from a new change. Bring older reports to your appointment.

5. Ask your doctor about anything flagged

   Your doctor can read the results alongside your symptoms, medicines and history, and decide whether to repeat a test or do more.

This page is general health information, not medical advice. DoctorAI is not a medical device and does not diagnose, treat, cure or prevent any condition. Talk to a doctor or other qualified health professional about your own results.