HomeBiomarkers

Biomarker library

Every blood test marker, explained

Each biomarker our AI lab test analyzer interprets — with reference ranges, what high or low means, and the clinical patterns to watch.

Complete Blood Count (CBC)

Hemoglobin HGB Oxygen-carrying protein in red blood cells. Low hemoglobin is the defining marker of anemia. Hematocrit HCT Percentage of blood volume occupied by red blood cells. Moves in parallel with hemoglobin. White Blood Cell Count WBC Total count of infection-fighting white cells. Subtypes (neutrophils, lymphocytes) carry far more diagnostic weight. Platelets PLT Cell fragments responsible for blood clotting. Critical for bleeding-risk assessment. Mean Corpuscular Volume MCV Average size of red blood cells. Categorizes anemia as microcytic, normocytic, or macrocytic.

Lipid Panel

Total Cholesterol CHOL Sum of LDL, HDL, and VLDL cholesterol. A starting point for cardiovascular risk — never interpreted alone. LDL Cholesterol LDL-C Low-density lipoprotein cholesterol. The primary driver of atherosclerotic plaque. HDL Cholesterol HDL-C High-density lipoprotein cholesterol. Carries cholesterol away from arteries to the liver. Triglycerides TG Storage form of fat in blood. Elevated levels raise risk of pancreatitis and cardiovascular disease.

Metabolic Panel

Fasting Glucose GLU Blood sugar after an 8-hour fast. First-line screen for prediabetes and diabetes. Hemoglobin A1c HbA1c Three-month average blood glucose. Standard for diabetes diagnosis and monitoring.

Kidney Panel

Creatinine CR Waste product of muscle metabolism, cleared by kidneys. Used to estimate eGFR. Estimated GFR eGFR Calculated kidney filtration rate. Defines chronic kidney disease (CKD) stage. Blood Urea Nitrogen BUN Nitrogen waste from protein breakdown. BUN/creatinine ratio helps differentiate causes of kidney injury.

Liver Panel

Alanine Aminotransferase ALT Liver-specific enzyme released when hepatocytes are damaged. Aspartate Aminotransferase AST Found in liver, heart, and muscle. AST/ALT ratio (De Ritis) > 2 suggests alcoholic liver disease. Alkaline Phosphatase ALP Enzyme from liver, bone, intestine, and placenta. Rises in biliary obstruction or bone turnover. Total Bilirubin TBIL Byproduct of red cell breakdown. Elevation causes jaundice.

Thyroid Panel

Thyroid-Stimulating Hormone TSH Pituitary hormone that controls thyroid output. The most sensitive screen for thyroid dysfunction. Free Thyroxine fT4 Active, unbound form of T4. Distinguishes primary from central thyroid disease. Free Triiodothyronine fT3 Active thyroid hormone at the tissue level. Useful in suspected T3-toxicosis.

Vitamins & Minerals

25-Hydroxy Vitamin D 25-OH D Best marker of vitamin D status. Deficiency is one of the most common findings in modern lab panels. Vitamin B12 B12 Water-soluble vitamin needed for nerve function, DNA, and red cell production. Folate B9 B-vitamin essential for DNA synthesis. Critical in pregnancy to prevent neural tube defects.

Iron Studies

Ferritin FER Storage form of iron. The single most useful marker for iron deficiency, with caveats in inflammation. Serum Iron FE Iron circulating bound to transferrin. Diurnal — highest in the morning. Transferrin Saturation TSAT Percentage of transferrin bound to iron. Best single marker for hereditary hemochromatosis screening.

Inflammation

C-Reactive Protein CRP Acute-phase protein produced by the liver. hs-CRP refines cardiovascular risk assessment. Erythrocyte Sedimentation Rate ESR Non-specific marker of inflammation. Useful for monitoring chronic inflammatory conditions.

Electrolytes

Sodium Na Primary extracellular cation. Dysregulation affects neurologic function. Potassium K Primary intracellular cation. Tight regulation is critical for cardiac rhythm. Calcium Ca Critical for nerve, muscle, bone, and clotting. Interpret with albumin or ionized calcium. Magnesium Mg Cofactor in 300+ enzymatic reactions. Commonly under-tested despite frequent subclinical deficiency.

How we wrote this library

Each biomarker page is drafted by a science writer and reviewed by a board-certified clinician — the same workflow we apply to our pillar articles. Reference ranges shown are typical adult intervals; the AI analyzer applies age-, sex-, and pregnancy-adjusted ranges at runtime.

If a biomarker your lab measures is not yet in the library, email hello@blood-test.life and we will add it within 72 hours.