Understanding Your Blood Test Results: A Patient's Guide to Common Lab Values

You've had blood drawn — now you're staring at a results page full of abbreviations, numbers, and reference ranges you don't understand. Blood test reports can feel like a foreign language. Here's a plain-English guide to the most common lab values and what they mean.

Complete Blood Count (CBC)

The CBC measures the cells in your blood and is one of the most commonly ordered tests.

WBC (White Blood Cell Count) — measures immune cells. Normal range: 4,500–11,000 cells/mcL. High WBC often indicates infection or inflammation. Low WBC can indicate immune suppression.

RBC (Red Blood Cell Count) — red cells carry oxygen. Normal: 4.5–5.5 million/mcL for men, 4.0–5.0 million/mcL for women. Low RBC is a marker of anemia.

Hemoglobin (Hgb) — the protein inside red cells that carries oxygen. Normal: 13.5–17.5 g/dL for men, 12.0–15.5 g/dL for women. Low hemoglobin is the clinical definition of anemia.

Platelets — normal range: 150,000–400,000/mcL. Low platelets (thrombocytopenia) can increase bleeding risk. High platelets may indicate inflammation or bone marrow conditions.

Comprehensive Metabolic Panel (CMP)

Glucose — blood sugar. Fasting normal: 70–100 mg/dL. 100–125 is pre-diabetic range. 126+ is diabetic range (if confirmed on repeat testing).

BUN (Blood Urea Nitrogen) — a waste product filtered by kidneys. Normal: 7–20 mg/dL. Elevated BUN can indicate dehydration or reduced kidney function.

Creatinine — another kidney waste marker. Normal: 0.74–1.35 mg/dL for men, 0.59–1.04 mg/dL for women. Elevated creatinine suggests reduced kidney filtration.

eGFR — estimates how well your kidneys filter blood. Normal: 60+ mL/min/1.73m². Stages of chronic kidney disease are defined by declining eGFR.

ALT and AST — liver enzymes. Normal: ALT 7–56 U/L, AST 10–40 U/L. Elevated values indicate liver stress from medications, alcohol, fatty liver disease, or hepatitis.

Lipid Panel

Total Cholesterol — desirable: under 200 mg/dL. LDL ("bad" cholesterol) — optimal: under 100 mg/dL. LDL particles can deposit in artery walls. HDL ("good" cholesterol) — higher is better; above 60 mg/dL is considered protective. Triglycerides — normal: under 150 mg/dL. Elevated triglycerides are associated with cardiovascular risk and can indicate insulin resistance.

HbA1c (Glycated Hemoglobin)

HbA1c measures average blood sugar over the past 2–3 months. Normal: under 5.7%. Pre-diabetic: 5.7–6.4%. Diabetic: 6.5% or higher. This test doesn't require fasting and is the primary monitoring tool for people managing diabetes.

Thyroid Tests

TSH (Thyroid Stimulating Hormone) — normal: 0.4–4.0 mIU/L. High TSH indicates an underactive thyroid (hypothyroidism). Low TSH indicates an overactive thyroid (hyperthyroidism). Free T4 is measured alongside TSH to confirm thyroid status.

When Results Are "Out of Range"

Reference ranges are population-based averages, not absolute thresholds. A result slightly outside the reference range is not automatically cause for alarm — your doctor interprets results in the context of your history, symptoms, and other values. A single abnormal value often warrants repeat testing before conclusions are drawn. If you have questions about your results, always contact your ordering physician rather than relying solely on internet searches.