Important: This guide helps you understand lab results but should never replace professional medical advice. Always discuss your results with your healthcare provider.
Getting lab results can feel overwhelming, especially when you're faced with numbers, abbreviations, and medical terms you don't understand. This comprehensive guide breaks down the most common lab tests, what the numbers mean, and when you should be concerned.
Understanding Lab Result Basics
How to Read Your Lab Report
Every lab report follows a similar format:
- Test Name: The specific test performed (e.g., "Glucose" or "Hemoglobin")
- Your Result: The numerical value or finding from your sample
- Reference Range: The normal range for healthy individuals
- Units: How the measurement is expressed (mg/dL, g/dL, etc.)
- Flag: Indicates if your result is high (H), low (L), or normal
Pro Tip: Understanding Ranges
Reference ranges can vary between labs due to different equipment and testing methods. Always use the range provided on your specific report, not general guidelines from the internet.
Complete Blood Count (CBC)
The CBC is one of the most common blood tests, providing information about your blood cells and overall health.
Red Blood Cell Tests
Hemoglobin (Hgb)
Normal Range: Men: 13.8-17.2 g/dL, Women: 12.1-15.1 g/dL
Measures oxygen-carrying protein in red blood cells. Low levels may indicate anemia; high levels could suggest dehydration or lung disease.
Hematocrit (Hct)
Normal Range: Men: 40.7-50.3%, Women: 36.1-44.3%
Percentage of blood volume made up of red blood cells. Should generally align with hemoglobin levels.
Red Blood Cell Count (RBC)
Normal Range: Men: 4.7-6.1 million/mcL, Women: 4.2-5.4 million/mcL
Total number of red blood cells. Used alongside other values to diagnose types of anemia.
White Blood Cell Tests
White Blood Cell Count (WBC)
Normal Range: 4,500-11,000 cells/mcL
Total number of infection-fighting cells. High counts may indicate infection or inflammation; low counts could suggest immune system problems.
Neutrophils
Normal Range: 50-70% of total WBC
Most common white blood cells that fight bacterial infections. High levels often indicate bacterial infection.
Lymphocytes
Normal Range: 20-40% of total WBC
Fight viral infections and help with immunity. High levels may indicate viral infection or certain blood cancers.
Basic Metabolic Panel (BMP)
The BMP checks your body's chemical balance and metabolism, including kidney function and blood sugar levels.
Glucose
Normal Range: 70-100 mg/dL (fasting)
Blood sugar level. High values may indicate diabetes or prediabetes. Values over 126 mg/dL (fasting) suggest diabetes.
Creatinine
Normal Range: Men: 0.7-1.3 mg/dL, Women: 0.6-1.1 mg/dL
Waste product filtered by kidneys. High levels may indicate kidney problems.
Blood Urea Nitrogen (BUN)
Normal Range: 6-24 mg/dL
Another waste product from protein breakdown. High levels may indicate kidney or heart problems.
Sodium (Na+)
Normal Range: 136-144 mEq/L
Important for fluid balance. Abnormal levels can indicate dehydration, kidney problems, or hormone imbalances.
Lipid Panel (Cholesterol Test)
Measures different types of cholesterol and fats in your blood, important for heart disease risk assessment.
Total Cholesterol
Desirable: Less than 200 mg/dL
Combined measurement of all cholesterol types. Higher levels increase heart disease risk.
LDL Cholesterol ("Bad" Cholesterol)
Optimal: Less than 100 mg/dL
Can build up in arteries and cause blockages. Lower is generally better for heart health.
HDL Cholesterol ("Good" Cholesterol)
Good: 40+ mg/dL (men), 50+ mg/dL (women)
Helps remove other cholesterol from arteries. Higher levels are protective for heart health.
Triglycerides
Normal: Less than 150 mg/dL
Type of fat in blood. High levels increase heart disease and pancreatitis risk.
Liver Function Tests
These tests check how well your liver is working and can detect liver damage or disease.
ALT (Alanine Aminotransferase)
Normal Range: 7-56 U/L
Enzyme found mainly in liver cells. High levels may indicate liver damage or inflammation.
AST (Aspartate Aminotransferase)
Normal Range: 10-40 U/L
Enzyme found in liver, heart, and muscle cells. Elevated levels can indicate liver or heart problems.
Bilirubin
Normal Range: 0.1-1.2 mg/dL
Waste product from red blood cell breakdown. High levels may cause jaundice and indicate liver problems.
Thyroid Function Tests
These tests evaluate how well your thyroid gland is functioning and producing hormones.
TSH (Thyroid Stimulating Hormone)
Normal Range: 0.4-4.0 mU/L
Hormone that tells thyroid to produce thyroid hormones. High TSH suggests underactive thyroid; low TSH suggests overactive thyroid.
T4 (Thyroxine)
Normal Range: 4.5-11.2 mcg/dL
Main thyroid hormone that regulates metabolism. Low levels indicate hypothyroidism; high levels indicate hyperthyroidism.
T3 (Triiodothyronine)
Normal Range: 100-200 ng/dL
Active form of thyroid hormone. Often tested when TSH or T4 are abnormal.
When to Be Concerned
Contact Your Doctor If:
- • Any result is significantly outside the normal range
- • You have multiple abnormal results
- • Results have changed dramatically from previous tests
- • You're experiencing symptoms that might relate to the results
- • You don't understand what the results mean
Factors That Can Affect Results
Many factors can influence your lab results:
- Time of day: Some tests require fasting or are affected by circadian rhythms
- Medications: Many drugs can alter lab values
- Diet: Recent meals can affect glucose, triglycerides, and other values
- Exercise: Physical activity can temporarily change some results
- Stress: Can affect hormone levels and other markers
- Illness: Even minor infections can alter results
- Dehydration: Can concentrate blood values
Questions to Ask Your Doctor
When reviewing your lab results with your healthcare provider, consider asking:
- What do these results tell us about my health?
- Are any results concerning or need follow-up?
- How do these compare to my previous results?
- Do I need any additional tests?
- Should I make any lifestyle changes based on these results?
- When should I repeat these tests?
- Are any of my medications affecting these results?
Remember
Lab results are just one piece of your health puzzle. Your doctor considers your symptoms, medical history, physical exam, and other factors alongside lab results to make medical decisions. One abnormal result doesn't necessarily mean you have a serious problem.
Getting the Most from Your Lab Tests
- Follow preparation instructions: Fast when required, avoid certain medications if advised
- Ask for copies: Keep your own records to track trends over time
- Schedule follow-up: Don't assume no news is good news
- Be proactive: Call with questions if results are unclear
- Consider timing: Some tests are best done at specific times
Understanding your lab results empowers you to be an active participant in your healthcare. While this guide provides general information about common tests, always work with your healthcare provider to interpret results in the context of your individual health situation.