Important Reminder
Lab results should always be reviewed with your healthcare provider. Reference ranges vary by lab, age, sex, and health status. This guide helps you understand common tests, but never self-diagnose based on lab results alone.
How to Read Your Lab Report
Test Name: What was measured
Your Result: Your actual number
Reference Range: Normal values for healthy people
Flag: H (High), L (Low), or nothing (Normal)
Units: How it's measured (mg/dL, mmol/L, etc.)
Complete Blood Count (CBC)
WBC (White Blood Cells)
Normal: 4,500-11,000 cells/mcL
What it means: Measures immune system cells that fight infection
• High: Infection, inflammation, leukemia, stress
• Low: Weakened immune system, bone marrow problems, some medications
RBC (Red Blood Cells)
Normal: Men 4.7-6.1 million/mcL | Women 4.2-5.4 million/mcL
What it means: Cells that carry oxygen throughout your body
• High: Dehydration, lung disease, living at high altitude
• Low: Anemia, bleeding, nutritional deficiencies
Hemoglobin (Hgb)
Normal: Men 13.5-17.5 g/dL | Women 12.0-15.5 g/dL
What it means: Protein in red blood cells that carries oxygen
• High: Dehydration, smoking, lung disease
• Low: Anemia, blood loss, iron/B12 deficiency
Platelets
Normal: 150,000-400,000/mcL
What it means: Cells that help blood clot
• High: Inflammation, iron deficiency, after surgery
• Low: Bleeding disorders, medications, autoimmune conditions
Metabolic Panel (CMP/BMP)
Glucose (Blood Sugar)
Fasting: 70-100 mg/dL | Random: Less than 200 mg/dL
What it means: Amount of sugar in your blood
• High: Prediabetes (100-125), Diabetes (126+), stress, medications
• Low: Not eating enough, too much insulin, liver disease
Creatinine
Normal: Men 0.74-1.35 mg/dL | Women 0.59-1.04 mg/dL
What it means: Waste product that shows how well kidneys are working
• High: Kidney disease, dehydration, high protein diet
• Low: Low muscle mass, malnutrition (rarely a concern)
BUN (Blood Urea Nitrogen)
Normal: 7-20 mg/dL
What it means: Another kidney function marker
• High: Kidney problems, dehydration, high protein diet, heart failure
• Low: Malnutrition, liver disease (rarely significant)
Lipid Panel (Cholesterol)
Total Cholesterol
Desirable: Less than 200 mg/dL
• Borderline high: 200-239 mg/dL
• High: 240+ mg/dL (increased heart disease risk)
LDL (“Bad” Cholesterol)
Optimal: Less than 100 mg/dL
• Near optimal: 100-129 mg/dL
• Borderline high: 130-159 mg/dL
• High: 160+ mg/dL
Lower is better for heart health
HDL (“Good” Cholesterol)
Goal: Men 40+ mg/dL | Women 50+ mg/dL
• Optimal: 60+ mg/dL (protective against heart disease)
• Low: Below 40 mg/dL (increased risk)
Higher is better for heart health
Triglycerides
Normal: Less than 150 mg/dL
• Borderline high: 150-199 mg/dL
• High: 200+ mg/dL
Affected by diet, alcohol, and diabetes control
Liver Function Tests
ALT & AST
Normal: ALT 7-56 U/L | AST 10-40 U/L
What it means: Enzymes released when liver is damaged
• High: Liver disease, hepatitis, alcohol use, medications, fatty liver
• Mild elevations (2-3x normal) often from fatty liver or medications
• Significant elevations need further evaluation
Thyroid Tests
TSH (Thyroid Stimulating Hormone)
Normal: 0.4-4.0 mIU/L
What it means: Signal from brain to thyroid gland
• High TSH: Underactive thyroid (hypothyroidism) - may feel tired, cold, weight gain
• Low TSH: Overactive thyroid (hyperthyroidism) - may feel anxious, rapid heartbeat, weight loss
When to Follow Up
Contact your doctor if:
- • Any values are marked “critical” or “panic”
- • Multiple values are abnormal
- • You have symptoms that match abnormal results
- • Values are significantly outside normal range
- • You don't understand what a result means
- • It's been more than a week and you haven't heard from your doctor
Important Things to Know
- •One abnormal value doesn't mean disease - May need repeat testing or further evaluation
- •Normal ranges vary by lab - Always compare to the reference range on YOUR report
- •Context matters - Age, sex, medications, and health status affect interpretation
- •Trends are important - Comparing to previous results shows patterns
- •Always follow fasting instructions - Eating can affect many test results
Medical Review
Reviewed by: Ricardo Hamilton, MD
Last Updated: November 26, 2025
Sources: Lab Corps Reference Ranges, Quest Diagnostics, American Association for Clinical Chemistry, Mayo Clinic Laboratory Manual
Medical Disclaimer: This guide provides general information only. Lab results must be interpreted by your healthcare provider in the context of your complete medical history, symptoms, and physical examination. Never make medical decisions based solely on lab results without consulting your doctor.