Blood Marker Guide
Plain-language explanations of the markers on your lab reports — what each one measures, what values outside the reference range can mean, and what to discuss with your doctor.
Blood count
- Basophils/uLBasophils are the rarest type of white blood cell.
- Eosinophils/uLEosinophils are white blood cells that help fight parasites and take part in allergic reactions and asthma.
- Haptoglobinmg/dLHaptoglobin is a protein made by the liver that binds free hemoglobin released when red blood cells break down.
- Hematocrit%Hematocrit is the percentage of your blood volume made up of red blood cells.
- Hemoglobing/dLHemoglobin is the protein in red blood cells that carries oxygen from your lungs to the rest of your body.
- Lymphocytes/uLLymphocytes are white blood cells central to the immune system, including the cells that fight viruses and make antibodies.
- MCHpgMCH (mean corpuscular hemoglobin) is the average amount of hemoglobin inside a single red blood cell.
- MCHCg/dLMCHC (mean corpuscular hemoglobin concentration) is the average concentration of hemoglobin within your red blood cells.
- MCVfLMCV (mean corpuscular volume) is the average size of your red blood cells.
- Monocytes/uLMonocytes are white blood cells that clear dead cells and microbes and help coordinate the immune response.
- MPVfLMPV (mean platelet volume) is the average size of your platelets, the cell fragments that help blood clot.
- Neutrophils/uLNeutrophils are the most common white blood cells and your body's first responders against bacterial infections.
- Platelets/uLPlatelets are tiny cell fragments that clump together to form clots and stop bleeding when a blood vessel is injured.
- RDW%RDW (red cell distribution width) measures how much your red blood cells vary in size.
- Red Blood Cells/uLThe red blood cell (RBC) count is the number of red cells in your blood.
- Reticulocytes%Reticulocytes are young, newly made red blood cells.
- White Blood Cells/uLThe white blood cell (WBC) count is the total number of immune cells in your blood that defend against infection.
Lipid panel
- Apolipoprotein A1mg/dLApolipoprotein A1 (ApoA1) is the main protein in HDL ("good") cholesterol particles.
- Apolipoprotein Bmg/dLApolipoprotein B (ApoB) is the main protein on LDL and other artery-clogging ("atherogenic") particles.
- Arachidonic Acid%Arachidonic acid (AA) is an omega-6 fatty acid, reported as a percentage of the fatty acids in your blood.
- Arachidonic Acid/EPA RatioratioThis ratio compares arachidonic acid (an omega-6) to EPA (an omega-3).
- DHA%DHA (docosahexaenoic acid) is a long-chain omega-3 fatty acid, reported as a percentage of your blood fatty acids.
- DPA%DPA (docosapentaenoic acid) is an omega-3 fatty acid that sits between EPA and DHA in the body's pathway, reported as a percentage of blood fatty acids.
- EPA%EPA (eicosapentaenoic acid) is a long-chain omega-3 fatty acid, reported as a percentage of blood fatty acids.
- HDL Cholesterolmg/dLHDL cholesterol is often called "good" cholesterol.
- LDL Cholesterolmg/dLLDL cholesterol is often called "bad" cholesterol.
- Linoleic Acid%Linoleic acid is the most common omega-6 fatty acid in the diet, reported as a percentage of blood fatty acids.
- Lipoprotein(a)mg/dLLipoprotein(a), or Lp(a), is an LDL-like particle with an extra protein attached.
- Non-HDL Cholesterolmg/dLNon-HDL cholesterol is your total cholesterol minus HDL.
- Omega-6/Omega-3 RatioratioThis ratio compares total omega-6 to total omega-3 fatty acids in your blood, summarising the overall balance of the two families.
- OmegaCheck%OmegaCheck measures the total of the main omega-3 fatty acids (EPA, DPA and DHA) in your blood, reported as a percentage of all fatty acids.
- Total Cholesterolmg/dLTotal cholesterol is the sum of all cholesterol in your blood, including HDL, LDL and a portion of triglyceride-rich particles.
- Triglyceridesmg/dLTriglycerides are the most common type of fat in the body, carried in the blood and used for energy.
- VLDL Cholesterolmg/dLVLDL (very-low-density lipoprotein) cholesterol is carried by particles that transport triglycerides.
Metabolic
- AmylaseU/LAmylase is an enzyme, made mainly by the pancreas and salivary glands, that helps digest carbohydrates.
- C-Peptideng/mLC-peptide is released in equal amounts to insulin when your pancreas makes it, so it shows how much insulin your body is producing.
- Calciummg/dLCalcium in the blood is a mineral essential for bones, nerves, muscles and clotting.
- ChloridemEq/LChloride is an electrolyte that works with sodium and other minerals to keep your body's fluids and acid-base balance in check.
- Creatine KinaseU/LCreatine kinase (CK) is an enzyme found mainly in muscle.
- Glucosemg/dLGlucose is the sugar your body uses for energy.
- Hemoglobin A1c%Hemoglobin A1c reflects your average blood sugar over the past two to three months by measuring sugar attached to hemoglobin.
- HOMA-IRratioHOMA-IR is a calculated index of insulin resistance, worked out from your fasting glucose and fasting insulin together.
- Homocysteineumol/LHomocysteine is an amino acid in the blood.
- InsulinmU/LInsulin is the hormone that moves sugar from your blood into cells for energy.
- Ionized Calciummmol/LIonized calcium is the active, free portion of calcium in your blood — the part the body actually uses, not bound to proteins.
- LDHU/LLDH (lactate dehydrogenase) is an enzyme found in almost every tissue.
- LipaseU/LLipase is an enzyme made mainly by the pancreas that helps digest fats.
- Magnesiummg/dLMagnesium is a mineral involved in hundreds of body processes, including muscle and nerve function, energy and a steady heartbeat.
- Methylmalonic Acidnmol/LMethylmalonic acid (MMA) is a substance that builds up when vitamin B12 is in short supply, making it a sensitive marker of B12 status.
- NT-proBNPpg/mLNT-proBNP is a fragment released by the heart when its walls are stretched or under strain.
- Phosphorusmg/dLPhosphorus is a mineral that works closely with calcium to build bones and teeth and to power energy use in cells.
- PotassiummEq/LPotassium is an electrolyte essential for nerve signals, muscle function and a steady heartbeat.
- SodiummEq/LSodium is an electrolyte that controls the balance of water in and around your cells, and supports nerve and muscle function.
- Troponin Ing/LTroponin I is a protein released into the blood when heart muscle is injured.
- Uric Acidmg/dLUric acid is a waste product formed when the body breaks down purines, substances found in some foods and in your own cells.
Kidney
- Creatininemg/dLCreatinine is a waste product from normal muscle activity that the kidneys filter out of the blood.
- eGFRmL/min/1.73m2eGFR (estimated glomerular filtration rate) estimates how much blood your kidneys filter each minute, calculated from creatinine, age and sex.
- Ureamg/dLUrea (also reported as BUN) is a waste product from the breakdown of protein, filtered out by the kidneys.
Liver
- Albuming/dLAlbumin is the most abundant protein in your blood, made by the liver.
- Alkaline PhosphataseU/LAlkaline phosphatase (ALP) is an enzyme found mainly in the liver and bones.
- ALTU/LALT (alanine aminotransferase) is an enzyme found mostly in the liver.
- ASTU/LAST (aspartate aminotransferase) is an enzyme found in the liver and also in muscle and other tissues.
- Direct Bilirubinmg/dLDirect (conjugated) bilirubin is the form the liver has already processed, ready to be removed in bile.
- GGTU/LGGT (gamma-glutamyl transferase) is an enzyme found in the liver and bile ducts.
- Indirect Bilirubinmg/dLIndirect (unconjugated) bilirubin is the form before the liver has processed it.
- Total Bilirubinmg/dLTotal bilirubin is the yellow pigment made when red blood cells break down.
- Total Proteing/dLTotal protein measures all the protein in your blood, mainly albumin and globulins together.
Thyroid
- Anti-ThyroglobulinIU/mLAnti-thyroglobulin antibodies are immune proteins that target thyroglobulin, a protein the thyroid uses to make its hormones.
- Anti-TPOIU/mLAnti-TPO antibodies target thyroid peroxidase, an enzyme the thyroid uses to make hormones.
- Anti-TRABUI/LTRAb (TSH-receptor antibodies) are antibodies that act on the thyroid's TSH receptor.
- Free T3pg/mLFree T3 is the active, unbound form of triiodothyronine, the more potent thyroid hormone that drives metabolism.
- Free T4ng/dLFree T4 is the unbound, available form of thyroxine, the main hormone the thyroid releases.
- Reverse T3ng/dLReverse T3 is an inactive form of thyroid hormone the body makes when converting T4.
- Thyroglobulinng/mLThyroglobulin is a protein made only by the thyroid.
- Total T3ng/dLTotal T3 measures all of the triiodothyronine in your blood, both the active free portion and the part bound to proteins.
- Total T4mcg/dLTotal T4 measures all the thyroxine in your blood, including the part bound to proteins and the small free, active fraction.
- TSHmUI/LTSH (thyroid-stimulating hormone) is made by the pituitary gland to tell the thyroid how much hormone to produce.
Hormones
- Cortisolmcg/dLCortisol is a hormone from the adrenal glands that helps manage stress, blood sugar, blood pressure and metabolism.
- DHEA-Smcg/dLDHEA-S is a hormone made by the adrenal glands.
- Estradiolpg/mLEstradiol is the main form of estrogen, a key sex hormone.
- Free Testosteronepmol/LFree testosterone is the small portion of testosterone not bound to proteins — the part readily available to your tissues.
- FSHUI/LFSH (follicle-stimulating hormone) is made by the pituitary gland to control the ovaries and testicles and support reproduction.
- IGF-1ng/mLIGF-1 (insulin-like growth factor 1) is made mainly by the liver in response to growth hormone.
- Leptinng/mLLeptin is a hormone released by fat cells that signals the brain about your energy stores and helps regulate appetite.
- LHUI/LLH (luteinizing hormone) is made by the pituitary gland.
- Progesteroneng/mLProgesterone is a hormone central to the menstrual cycle and pregnancy.
- Prolactinmcg/LProlactin is a pituitary hormone best known for enabling breast-milk production.
- PSA % Free%Free PSA percentage is the share of your PSA that circulates unbound.
- PSA Freeng/mLFree PSA is the portion of prostate-specific antigen circulating unbound to proteins.
- PSA Totalng/mLPSA (prostate-specific antigen) is a protein made by the prostate.
- PTHpg/mLParathyroid hormone (PTH) is made by four small glands in the neck and is the main regulator of calcium in your blood.
- SHBGnmol/LSHBG (sex hormone-binding globulin) is a protein that binds sex hormones, especially testosterone, controlling how much is freely available.
- Testosteroneng/dLTestosterone is the main male sex hormone, also present in smaller amounts in women.
Vitamins & minerals
- Coppermcg/dLCopper is a trace mineral your body needs in small amounts for energy production, iron handling, nerves and connective tissue.
- Folic Acidng/mLFolate (folic acid) is a B vitamin essential for making DNA, dividing cells and forming healthy red blood cells.
- Ironmcg/dLSerum iron measures the amount of iron circulating in your blood, bound to a transport protein.
- Leadmcg/dLBlood lead measures exposure to lead, a toxic metal with no useful role in the body.
- Magnesium RBCmg/dLRBC magnesium measures magnesium inside red blood cells, which some clinicians use as a fuller picture of magnesium stores than the standard blood test.
- Omega-3 Index%The Omega-3 Index is the percentage of EPA and DHA (omega-3 fats) in your red blood cell membranes, reflecting long-term omega-3 status.
- Seleniummcg/LSelenium is a trace mineral that acts as an antioxidant and supports thyroid and immune function.
- TIBCmcg/dLTIBC (total iron-binding capacity) measures how much iron your blood could carry — essentially the number of available "seats" on the iron-transport protein.
- Transferrin Saturation%Transferrin saturation is the percentage of your iron-transport protein that is actually carrying iron — how "full" your iron taxis are.
- Vitamin Amcg/dLVitamin A is a fat-soluble vitamin important for vision, immune function, skin and cell growth.
- Vitamin B12ng/LVitamin B12 is essential for nerve function, DNA and forming healthy red blood cells.
- Vitamin B6ng/mLVitamin B6 is a B vitamin involved in metabolism, nerve function, and the making of hemoglobin and neurotransmitters.
- Vitamin Dng/mLVitamin D helps your body absorb calcium and supports bones, muscles and the immune system.
- Vitamin Emg/LVitamin E is a fat-soluble antioxidant that helps protect cells from damage and supports immune function.
- Zincmcg/dLZinc is a trace mineral the body needs for immune function, wound healing, taste, smell and many enzymes.
Inflammation
- CRPmg/dLC-reactive protein (CRP) is made by the liver and rises quickly when there is inflammation anywhere in the body.
- ESRmm/hESR (erythrocyte sedimentation rate) measures how fast red blood cells settle in a tube — a simple, indirect sign of inflammation.
- Ferritinmcg/LFerritin is the protein that stores iron in your body.
- High-Sensitivity CRPmg/dLHigh-sensitivity CRP measures very low levels of C-reactive protein, fine enough to gauge the low-grade inflammation linked to heart risk.
- Rheumatoid FactorIU/mLRheumatoid factor (RF) is an antibody that can be present in rheumatoid arthritis and some other autoimmune conditions.
Coagulation
- aPTTsaPTT (activated partial thromboplastin time) measures how long part of your blood-clotting process takes to form a clot.
- D-Dimerng/mLD-dimer is a small fragment left behind when a blood clot breaks down.
- Fibrinogenmg/dLFibrinogen is a protein made by the liver that is essential for blood to clot.
- INRratioINR (international normalized ratio) is a standardized version of the prothrombin time, so clotting results compare across labs.
- Prothrombin TimesProthrombin time (PT) measures how long your blood takes to clot through one of its main pathways.
Other laboratory
Vital signs
- Blood Pressure - DiastolicmmHgDiastolic blood pressure is the lower number — the pressure in your arteries between heartbeats, while the heart rests and refills.
- Blood Pressure - SystolicmmHgSystolic blood pressure is the higher number — the pressure in your arteries when your heart beats and pushes blood out.
- Body Temperature°CBody temperature reflects the balance of heat your body produces and loses.
- Heart RatebpmHeart rate is the number of times your heart beats per minute.
- Heart Rate VariabilitymsHeart rate variability (HRV) is the natural variation in time between heartbeats.
- Oxygen Saturation%Oxygen saturation (SpO2) is the percentage of your red blood cells carrying oxygen, usually measured with a fingertip sensor.
- Resting Heart RatebpmResting heart rate is how many times your heart beats per minute when you are calm and at rest.
- WeightkgWeight is your body mass.