CBC Blood Test Explained: What Those 10 Indicators Reveal About Your Health

Your health report shows the CBC page with several rows marked with up or down arrows. You glance at it, don't understand what these numbers mean, and flip to the next page.

If you do this too, you might be missing an opportunity to understand your body's condition.

CBC, or Complete Blood Count, is one of the most basic and inexpensive health screening items, but also one of the most informative. A single CBC report can tell you if your body is experiencing infection, anemia, immune status, and even certain blood diseases.

CBC tests three types of blood cells: red blood cells, white blood cells, and platelets.

Red blood cells carry oxygen—inhaled oxygen from lungs to all body tissues and organs, then bring back carbon dioxide. Low red blood cell count or hemoglobin means anemia.

White blood cells are your body's immune cells, responsible for fighting infection and clearing abnormal cells. Changes in white blood cell count often indicate your body is undergoing some immune response.

Platelets are responsible for clotting. When vessels are damaged, platelets gather to form clots and stop bleeding. Abnormal platelet counts may mean bleeding risk or clotting risk.

The red blood cell series has several indicators, but the most important is hemoglobin.

Hemoglobin is the oxygen-carrying protein in red blood cells, and its content directly determines blood's oxygen-carrying capacity. Normal adult male hemoglobin is 120-160 g/L, females 110-150 g/L.

Below this range is anemia. But anemia isn't simply "less blood"—it's reduced oxygen-carrying capacity. Mild anemia may have no obvious symptoms, just easy fatigue, shortness of breath after exercise. Moderate to severe anemia may show pale complexion, dizziness, palpitations, poor concentration.

High hemoglobin isn't necessarily good. Significantly above normal range could be polycythemia—a bone marrow proliferation disease where increased blood viscosity raises clot risk. It could also just be temporarily elevated from living at high altitude, smoking, or dehydration.

Hematocrit is the percentage of red blood cells by blood volume, similar in meaning to hemoglobin. MCV reflects red blood cell size. MCH and MCHC reflect hemoglobin content in red blood cells. These indicators help determine anemia type—is it microcytic (like iron deficiency anemia), macrocytic (like megaloblastic anemia), or normocytic anemia.

The most important indicator in the white blood cell series is white blood cell count, normal range 4-10×10^9/L.

Elevated white blood cells most commonly indicate infection. Bacterial infection typically causes elevated neutrophil proportion, significantly elevated total white count. Viral infection may cause elevated lymphocyte proportion, but total white count may be normal or decreased.

But this isn't absolute. Certain severe bacterial infections (like typhoid)反而 cause decreased white count. Certain viral infections (like infectious mononucleosis) can cause abnormally elevated white count.

Elevated white blood cells could also be from other causes: severe tissue injury (like burns, trauma), acute stress (like after intense exercise), certain medications (like corticosteroids), or even leukemia.

Decreased white blood cells need vigilance. Below 3×10^9/L is leukopenia, below 2×10^9/L is moderate decrease, below 1×10^9/L is severe decrease. Decreased white count means compromised immunity, significantly increased infection risk. Possible causes include viral infection (like flu), medication side effects (like certain antibiotics, chemo drugs), radiation exposure, autoimmune diseases, or bone marrow dysfunction.

White blood cell differential count is more specific. Neutrophils are the body's main force against bacterial infection, accounting for 50-70%. Lymphocytes are responsible for fighting viral infection and producing antibodies, 20-40%. Monocytes clean up large pathogens and cell debris, 3-8%. Eosinophils relate to allergic reactions and parasitic infections, 0.5-5%. Basophils are rarest but also relate to allergic reactions.

Normal platelet range is 100-300×10^9/L.

Below 100×10^9/L is thrombocytopenia. Mild decrease (50-100) may have no obvious symptoms, moderate (20-50) may show skin bruising, gum bleeding, nose bleeds. Severe decrease (＜20) has risk of internal bleeding, intracranial hemorrhage—needs immediate medical attention.

Causes of thrombocytopenia include: viral infection (like flu, dengue), medication side effects (like aspirin, certain antibiotics), autoimmune diseases (like ITP), bone marrow dysfunction (like aplastic anemia, leukemia), or hypersplenism.

Above 450×10^9/L is thrombocytosis. Mild elevation may be reactive—infection, inflammation, iron deficiency, post-surgery. Significant elevation (>600) could be primary thrombocytosis, a bone marrow proliferation disease with both clot and bleeding risks.

Mean platelet volume (MPV) reflects platelet size. Newly produced platelets are larger, aging platelets smaller. Elevated MPV may indicate increased platelet destruction or active bone marrow production. Lower MPV may indicate suppressed bone marrow production.

CBC abnormalities don't necessarily mean disease, but some situations need special attention:

Extremely elevated white count (>20×10^9/L) or extremely low (＜2×10^9/L) needs immediate medical attention. Could be severe infection, leukemia, or other serious diseases.

Hemoglobin below 70 g/L is moderate to severe anemia, may need transfusion or detailed investigation. Below normal but above 90 may be mild anemia—can be investigated electively.

Platelets below 50×10^9/L have bleeding risk, below 20×10^9/L have severe bleeding risk—needs immediate medical attention. Platelets above 600×10^9/L need hematology referral to rule out bone marrow proliferation disease.

CBC finding abnormal cells (like immature cells, atypical lymphocytes) needs hematology consultation. Could be leukemia, lymphoma, or other blood diseases signaling.

CBC is just one part of your health report. Use our Blood Panel Interpreter tool below to comprehensively understand your report, including CBC, liver function, kidney function, lipids, glucose, and other indicators.

Enter your test results, and the system will tell you what each indicator means, possible causes, recommended next steps.

CBC is one of the cheapest but most valuable screening items. A test costing only tens of yuan can tell you if your body is experiencing infection, anemia, immune status, and blood system health.

At your next checkup, look carefully at the CBC page. If there are arrows, don't panic but don't ignore. Combine with your symptoms and signs, consult your doctor if needed, or use our interpretation tool.

Remember, CBC abnormalities don't necessarily mean serious disease, but they are signals your body sends. Pay attention to these signals to catch problems early and address them promptly.

Use our Blood Panel Interpreter tool above to start understanding your health report. Health begins with understanding.