Lab biomarker guide
Understand what your lab tests measure, what the results mean, and how to track changes over time.
Blood Urea Nitrogen
Blood urea nitrogen (BUN) measures nitrogen from urea, a waste product of protein breakdown that the kidneys filter, serving as a marker of kidney function.
Carbon Dioxide (Bicarbonate)
Carbon dioxide (CO2), or bicarbonate, measures the body's acid-base balance, reflecting the bicarbonate buffering system that keeps blood pH within normal limits.
Chloride
Chloride is the major anion in blood and extracellular fluid, working with sodium to maintain fluid balance, blood pressure, and acid-base balance.
Creatinine
Creatinine is a muscle-metabolism waste product cleared by the kidneys, serving as a reliable marker of kidney function and the basis for calculating eGFR.
Cystatin C
Cystatin C is a small protein made by all nucleated cells that serves as a marker of kidney function, unaffected by muscle mass, age, sex, or race.
eGFR (Estimated GFR)
Estimated glomerular filtration rate (eGFR) is a calculated measure of kidney function, estimating how much blood the kidneys filter per minute.
Fasting Insulin
Fasting insulin measures blood insulin after at least 8 hours without food; insulin regulates glucose, and high fasting levels often signal insulin resistance.
Fructosamine
Fructosamine is a glycated protein, formed when glucose binds to albumin, that reflects average blood sugar over the previous 2-3 weeks.
Glucose
Glucose is the primary sugar in the blood and the main energy source for the body's cells, reflecting how the body processes sugar and uses insulin.
HbA1c (DCCT)
HbA1c (hemoglobin A1c) measures the percentage of hemoglobin with glucose attached, a stable indicator of average blood sugar over the past 2-3 months.
HbA1c (IFCC)
HbA1c (IFCC) is hemoglobin A1c reported in mmol/mol, measuring the percentage of hemoglobin with glucose attached to reflect average blood sugar over 2-3 months.
Lactate (Lactic Acid)
Lactate (lactic acid) is a byproduct of anaerobic metabolism formed when cells lack oxygen, serving as an indicator of tissue oxygenation and metabolic stress.
Phosphate
Phosphate is an essential mineral central to bone formation, energy metabolism, and cellular function, working with calcium to maintain bone health.
Potassium
Potassium is the major intracellular cation, essential for muscle and nerve function, heart rhythm regulation, and cellular fluid balance.
Sodium
Sodium is the major extracellular cation that regulates fluid balance, blood pressure, and nerve function, and helps maintain hydration and blood volume.
Uric Acid
Uric acid is a waste product formed when the body breaks down purines; excess levels can form crystals in joints and tissues.
BUN/Creatinine Ratio
The BUN/creatinine ratio compares blood urea nitrogen to creatinine, helping distinguish the underlying causes of kidney dysfunction.
Estimated Average Glucose
Estimated average glucose (eAG) translates HbA1c into an average blood glucose level over the past 2-3 months, expressed in everyday glucose-meter units.
HOMA-IR
HOMA-IR estimates insulin resistance from fasting glucose and insulin levels, with higher values indicating greater insulin resistance.
CA-125
CA-125 is a protein that can be elevated in certain cancers, particularly ovarian cancer, though it is not cancer-specific and also rises in benign conditions.
PSA (Free)
Free PSA is the unbound fraction of prostate-specific antigen in blood, used alongside total PSA to distinguish benign prostate conditions from cancer.
PSA (Total)
Prostate-specific antigen (PSA) is a protein made by prostate cells; total PSA includes both free and bound forms and is used mainly for cancer screening.
Basophils (Absolute)
Basophils (absolute) is the number of basophils per microliter of blood, the rarest white blood cells, involved in allergic reactions and inflammatory responses.
Basophils %
Basophils % is the proportion of basophils among total white blood cells, the rarest white cell type, which drive allergic reactions and inflammatory responses.
Eosinophils (Absolute)
Eosinophils (absolute) counts the eosinophils per microliter of blood, white cells that combat parasitic infections and mediate allergic responses.
Eosinophils %
Eosinophils % is the share of eosinophils among total white blood cells, cells that fight parasitic infections and drive allergic reactions and asthma.
Hematocrit
Hematocrit measures the percentage of blood volume occupied by red blood cells, reflecting the blood's oxygen-carrying capacity and red blood cell concentration.
Hemoglobin
Hemoglobin is the iron-containing protein in red blood cells that carries oxygen from the lungs to tissues and returns carbon dioxide to the lungs.
Immature Granulocytes
Immature granulocytes are young white blood cells normally confined to bone marrow; in blood they signal rapid production from infection, inflammation, or stress.
Immature Granulocytes %
Immature granulocytes % is the share of developing neutrophils among total white blood cells, rising when demand for infection-fighting cells increases.
Large Immature Cells
Large immature cells (LIC) is the absolute count of large immature cells, including blasts and abnormal lymphocytes, normally absent or rare in healthy blood.
Large Immature Cells %
Large immature cells % is the share of large immature cells, including blasts and abnormal lymphocytes, among white blood cells, normally absent from blood.
Lymphocytes (Absolute)
Lymphocytes (absolute) is the number of lymphocytes per microliter of blood, immune cells including T cells, B cells, and natural killer cells.
Lymphocytes %
Lymphocytes % is the proportion of lymphocytes among total white blood cells, the T cells, B cells, and natural killer cells of the adaptive immune system.
Mean Corpuscular Hemoglobin
Mean Corpuscular Hemoglobin (MCH) is the average amount of hemoglobin in each red blood cell, used to classify different types of anemia.
Mean Corpuscular Hemoglobin Concentration
Mean Corpuscular Hemoglobin Concentration (MCHC) is the average hemoglobin concentration in red blood cells, useful for diagnosing specific anemia types.
Mean Corpuscular Volume
Mean Corpuscular Volume (MCV) is the average size of red blood cells, used to classify anemia as microcytic, normocytic, or macrocytic.
Mean Platelet Volume
Mean Platelet Volume (MPV) is the average size of platelets in blood, providing insight into platelet production and turnover.
Monocytes (Absolute)
Monocytes (absolute) is the number of monocytes per microliter of blood, large white blood cells that engulf bacteria, dead cells, and debris.
Monocytes %
Monocytes % is the proportion of monocytes among total white blood cells, large immune cells that migrate into tissues and mature into macrophages.
Neutrophils (Absolute)
Neutrophils (absolute) is the number of neutrophils per microliter of blood, the most abundant white cells defending against bacterial and fungal infections.
Neutrophils %
Neutrophils % is the proportion of neutrophils among all white blood cells, the most abundant white cells and primary defense against bacterial infection.
Nucleated RBC %
Nucleated RBC % is the proportion of immature, nucleus-retaining red blood cells in a sample, whose presence typically signals bone marrow stress.
Nucleated Red Blood Cells
Nucleated red blood cells (NRBC) is the count of immature, nucleus-containing red cells, whose presence in blood signals stress on the blood-forming system.
Platelet Count
Platelet count measures the number of platelets per microliter of blood, the cell fragments that clump to form clots and prevent excessive bleeding.
Platelet Distribution Width
Platelet distribution width (PDW) measures the variation in platelet size within a blood sample, reflecting the heterogeneity of circulating platelets.
Platelet Distribution Width (CV)
Platelet distribution width (PDW-CV) is the coefficient of variation in platelet size, quantifying how much individual platelets vary from the average.
Plateletcrit
Plateletcrit (PCT) measures the percentage of blood volume occupied by platelets, reflecting the total platelet mass in circulation.
Red Blood Cell Count
Red blood cell count (RBC) measures the number of red blood cells per microliter of blood, the cells that carry oxygen from the lungs to body tissues.
Red Cell Distribution Width
Red cell distribution width (RDW) measures the variation in red blood cell size within a blood sample, useful for differentiating types of anemia.
White Blood Cell Count
White blood cell count (WBC) measures the total white blood cells per microliter of blood, the immune cells that defend against infection.
Creatine Kinase
Creatine kinase (CK) is an enzyme found in skeletal muscle, heart, and brain that leaks into the blood when muscle cells are damaged, marking muscle injury.
Lactate Dehydrogenase
Lactate dehydrogenase (LDH) is an enzyme found in nearly all tissues that aids energy production and is released into the blood when tissue is damaged.
Lead (Blood)
Blood lead measures recent exposure to lead, a toxic heavy metal with no biological function that accumulates in bones, teeth, and soft tissues.
Mercury (Blood)
Mercury (blood) measures exposure to mercury, a toxic heavy metal occurring in elemental, inorganic, and organic (methylmercury) forms.
Anti-Müllerian Hormone
Anti-Müllerian hormone (AMH) is a protein hormone made by developing egg follicles and the most reliable marker of ovarian reserve.
Bioavailable Testosterone
Bioavailable testosterone is the portion that is free or loosely albumin-bound and available to tissues, calculated from total testosterone, SHBG, and albumin.
Cortisol
Cortisol is the primary stress hormone made by the adrenal glands, regulating blood pressure, blood sugar, and inflammation and following a daily circadian rhythm.
DHEA Sulfate
DHEA sulfate (DHEA-S) is an adrenal hormone precursor and reservoir for making testosterone and estrogen, reflecting adrenal gland function.
Estradiol
Estradiol is the most potent and abundant form of estrogen, regulating the menstrual cycle, supporting bone health, and maintaining reproductive tissue.
Follicle Stimulating Hormone
Follicle-stimulating hormone (FSH) is a pituitary hormone that drives reproductive function, stimulating egg development in women and sperm production in men.
Free Androgen Index
Free androgen index (FAI) is the ratio of total testosterone to SHBG, expressed as a percentage to estimate biologically active testosterone.
Free Testosterone
Free testosterone is the small fraction (1-3%) of testosterone circulating unbound to proteins, the most biologically active form available to cells.
Insulin-Like Growth Factor 1
Insulin-like growth factor 1 (IGF-1) is a liver-made hormone produced in response to growth hormone and a stable, reliable indicator of growth hormone activity.
Luteinizing Hormone
Luteinizing hormone (LH) is a pituitary hormone central to reproduction, triggering ovulation in women and stimulating testosterone production in men.
Progesterone
Progesterone is a steroid hormone made by the corpus luteum and placenta that prepares the uterine lining for implantation and regulates the menstrual cycle.
Prolactin
Prolactin is a pituitary hormone that primarily stimulates breast milk production after childbirth and also influences reproduction and metabolism.
Sex Hormone Binding Globulin
Sex hormone binding globulin (SHBG) is a liver-made protein that binds and transports sex hormones, regulating how much remains free and active.
Total Testosterone
Total testosterone measures both free and bound testosterone, the primary male sex hormone affecting muscle mass, bone density, and libido.
C-Reactive Protein
C-reactive protein (CRP) is a liver-made protein that rises rapidly with inflammation anywhere in the body, serving as a sensitive marker of inflammatory activity.
Erythrocyte Sedimentation Rate
Erythrocyte sedimentation rate (ESR) measures how quickly red blood cells settle in a tube over one hour, serving as a nonspecific marker of inflammation.
Fibrinogen
Fibrinogen is a liver-made protein that converts to fibrin to form blood clots and acts as an acute-phase reactant that rises with inflammation.
Immunoglobulin E
Immunoglobulin E (IgE) is an antibody class central to allergic reactions and parasitic infections, triggering hypersensitivity when it meets specific allergens.
Ferritin
Ferritin is a blood protein that reflects stored iron and the most reliable single marker for assessing iron status, deficiency, or overload.
Iron (Serum)
Serum iron measures the iron bound to transferrin in the blood at testing; essential for oxygen transport, it fluctuates through the day and with meals.
Iron Saturation
Iron saturation, or transferrin saturation, is the percentage of transferrin that is actually carrying iron, calculated from serum iron and TIBC.
Total Iron Binding Capacity
Total iron binding capacity (TIBC) measures the maximum iron that transferrin and other proteins in blood can bind, primarily reflecting transferrin levels.
Transferrin
Transferrin is the primary iron transport protein in blood, carrying iron from absorption and storage sites to tissues such as the bone marrow.
Apolipoprotein B
Apolipoprotein B (ApoB) is the main protein on LDL particles and, with one per particle, gives a direct count of potentially harmful particles in blood.
HDL Cholesterol
HDL (high-density lipoprotein) is the 'good' cholesterol that carries cholesterol from tissues back to the liver; higher levels mean lower cardiovascular risk.
LDL Cholesterol
LDL (low-density lipoprotein) is the 'bad' cholesterol that carries cholesterol from the liver to tissues and can deposit it in artery walls, forming plaque.
LDL Particle Number
LDL particle number (LDL-P) is the total count of LDL particles in the blood, regardless of size or cholesterol content, distinct from standard LDL cholesterol.
LDL/HDL Ratio
LDL/HDL ratio compares 'bad' LDL cholesterol to 'good' HDL cholesterol, reflecting the balance between cholesterol deposited in arteries and removed for disposal.
Lipoprotein(a)
Lipoprotein(a), or Lp(a), is an LDL-like lipoprotein particle carrying apolipoprotein(a), with blood levels almost entirely determined by genetics.
Non-HDL Cholesterol
Non-HDL cholesterol is total cholesterol minus HDL, capturing all atherogenic cholesterol-carrying particles including LDL and VLDL.
Total Cholesterol
Total cholesterol measures all cholesterol in the blood, including LDL, HDL, and VLDL, serving as an initial screening tool for cardiovascular risk.
Total Cholesterol/HDL Ratio
The total cholesterol/HDL ratio compares total cholesterol to protective HDL cholesterol as a simple measure of cardiovascular risk.
Triglyceride/HDL Ratio
The Triglyceride/HDL (TG/HDL) ratio divides triglyceride by HDL cholesterol, serving as a surrogate marker for insulin resistance and metabolic health.
Triglycerides
Triglycerides are the most common type of fat in the blood, formed when the body converts excess calories into fat for storage and energy.
VLDL Cholesterol
VLDL (very low-density lipoprotein) cholesterol is the cholesterol within VLDL particles, which carry triglycerides from the liver to body tissues.
Albumin
Albumin is the most abundant protein in blood plasma, made by the liver, reflecting both liver synthetic function and overall nutritional status.
Albumin/Globulin Ratio
The albumin/globulin (A/G) ratio compares albumin to globulin proteins in blood, reflecting the balance between liver synthetic function and immune activity.
Alkaline Phosphatase
Alkaline phosphatase (ALP) is an enzyme concentrated in the liver, bones, and bile ducts, released when these tissues are damaged or during bone growth.
ALT (Alanine Aminotransferase)
ALT (alanine aminotransferase) is an enzyme found mainly in liver cells and one of the most specific blood markers of liver injury when those cells are damaged.
AST (Aspartate Aminotransferase)
AST (aspartate aminotransferase) is an enzyme found in the liver, heart, and muscle, released into blood when those tissues are damaged to mark tissue injury.
Direct Bilirubin
Direct (conjugated) bilirubin is the water-soluble form processed by the liver, measuring the liver-conjugated portion of total bilirubin.
Gamma-Glutamyl Transferase
Gamma-glutamyl transferase (GGT) is a liver and bile duct enzyme and one of the most sensitive markers for detecting liver and bile duct disorders.
Globulin
Globulin is a group of blood proteins including antibodies, transport proteins, and enzymes, serving roles in immunity and substance transport.
Total Bilirubin
Total bilirubin measures bilirubin, a yellow pigment from red blood cell breakdown, serving as a marker of liver function and red blood cell turnover.
Total Protein
Total protein measures all proteins in blood serum, primarily albumin and globulins, reflecting liver function, immune activity, and nutritional status.
Arachidonic Acid
Arachidonic acid (AA) is an omega-6 fatty acid measured as a percentage of total blood fatty acids and a precursor to inflammatory compounds called eicosanoids.
Omega-3 Total
Omega-3 total measures the combined percentage of EPA and DHA fatty acids in blood, essential fats the body cannot produce on its own.
Omega-6 Total
Omega-6 total measures the percentage of omega-6 fatty acids in blood, including linoleic and arachidonic acid, essential but pro-inflammatory fats.
Omega-6:Omega-3 Ratio
The omega-6:omega-3 ratio compares pro-inflammatory omega-6 to anti-inflammatory omega-3 fatty acids in blood, a measure of inflammatory balance.
Amylase
Amylase is a digestive enzyme made mainly by the pancreas and salivary glands that breaks down starches, used to detect pancreatic or salivary gland problems.
Lipase
Lipase is a digestive enzyme produced mainly by the pancreas that breaks down dietary fats, and a reliable marker of pancreatic disorders and inflammation.
Free T3
Free T3 (triiodothyronine) is the active, unbound form of thyroid hormone T3, the fraction immediately available to enter cells and regulate metabolism.
Free T4
Free T4 measures the unbound, metabolically active portion of thyroxine, unaffected by protein binding and reflecting thyroid hormone available to tissues.
Thyroglobulin Antibodies
Thyroglobulin antibodies (TG-Ab) are autoantibodies against thyroglobulin, a thyroid protein, indicating an autoimmune response against thyroid tissue.
Thyroid Peroxidase Antibodies
Thyroid peroxidase antibodies (TPO-Ab) target thyroid peroxidase, an enzyme needed for hormone production, signaling an immune attack on the thyroid gland.
Thyroid Stimulating Hormone
Thyroid stimulating hormone (TSH) is made by the pituitary gland and regulates thyroid hormone production, rising when thyroid hormones are low.
Total T3
Total T3 (triiodothyronine) measures all T3 thyroid hormone in the blood, including both protein-bound and free, active forms.
Total T4
Total T4 (thyroxine) measures free and protein-bound T4, the primary thyroid hormone, which tissues convert to the more active T3.
Albumin/Creatinine Ratio (Urine)
The albumin/creatinine ratio (ACR) is a urine test measuring albumin relative to creatinine, used to screen for kidney damage while accounting for urine concentration.
Microalbumin (Urine)
Microalbumin (urine) measures small amounts of the protein albumin in urine, where even tiny levels can signal early kidney damage.
Urine Bilirubin
Urine bilirubin detects conjugated (water-soluble) bilirubin in urine, which spills over when liver function is impaired or bile flow is blocked.
Urine Blood (Occult)
The urine occult blood test detects red blood cells or hemoglobin not visible to the eye, indicating bleeding somewhere in the urinary tract.
Urine Glucose
Urine glucose measures sugar in urine; healthy kidneys reabsorb it, so its presence often signals blood sugar control problems.
Urine Ketones
Urine ketones are byproducts of fat metabolism that appear when the body breaks down fat for energy instead of glucose, spilling into urine.
Urine Leukocyte Esterase
Leukocyte esterase is an enzyme from white blood cells; the urine test detects it as a sign of infection or inflammation in the urinary tract.
Urine Nitrite
Urine nitrite detects bacteria that convert urinary nitrates into nitrites, serving as a specific indicator of bacterial urinary tract infections.
Urine pH
Urine pH measures how acidic or alkaline urine is on a 0-14 scale, reflecting the kidneys' ability to maintain acid-base balance.
Urine Protein
Urine protein measures total protein in urine; since healthy kidneys retain protein in the blood, its presence often indicates kidney damage.
Urine Specific Gravity
Urine specific gravity measures how concentrated urine is compared with pure water, reflecting kidney concentrating ability and hydration status.
Urine Urobilinogen
Urine urobilinogen is a bilirubin breakdown product made by intestinal bacteria, normally present in small amounts in urine.
Calcium
Calcium is the body's most abundant mineral, essential for bones and teeth, muscle contraction, nerve transmission, and blood clotting.
Calcium (Corrected)
Corrected calcium adjusts total calcium for albumin level to better reflect biologically active calcium, since about half of blood calcium is bound to albumin.
Folate
Folate (vitamin B9) is an essential B vitamin needed for DNA synthesis, red blood cell formation, and fetal development, obtained only from diet.
Homocysteine
Homocysteine is an amino acid produced when methionine is broken down during protein metabolism; high levels are linked to cardiovascular disease and stroke risk.
Magnesium
Magnesium is an essential mineral involved in over 300 enzymatic reactions, supporting muscle and nerve function, bone health, and energy production.
Selenium
Selenium is an essential trace mineral with antioxidant properties, a component of selenoproteins that supports thyroid hormone metabolism and immune function.
Vitamin B12
Vitamin B12 (cobalamin) is an essential nutrient for red blood cell formation, neurological function, and DNA synthesis that the body cannot produce.
Vitamin D (25-Hydroxy)
Vitamin D (25-hydroxy) is the primary storage form of vitamin D and the best indicator of vitamin D status, reflecting sun exposure and dietary intake.
Zinc
Zinc is an essential trace mineral involved in over 300 enzyme reactions, supporting immune function, wound healing, protein synthesis, and growth.