White Blood Cell Count
The number of infection-fighting cells in a volume of blood.
Understand your health
You got a lab report full of abbreviations and a note saying "results normal" or "call the office." Here is what each of those tests actually measures, in plain English, and what to ask about it.
Build a questions sheet for your appointment
112 tests explained so far, grouped by the panel they usually arrive in.
Complete Blood Count (CBC)
Counts and measures the cells in your blood. One of the most commonly ordered panels there is.
Hemoglobin
The oxygen-carrying protein inside red blood cells.
Hematocrit
The percentage of your blood volume made up of red blood cells.
Mean Corpuscular Volume
The average size of your red blood cells.
Platelet Count
The cells that let blood clot.
Red Cell Distribution Width
How much your red blood cells vary in size from one another.
Red Blood Cell Count
The number of red blood cells in a set volume of blood - the cells that carry oxygen.
Mean Corpuscular Hemoglobin
The average amount of hemoglobin inside each individual red blood cell.
Mean Corpuscular Hemoglobin Concentration
How densely hemoglobin is packed into red blood cells, on average.
Mean Platelet Volume
The average size of platelets, the small cell fragments that help blood clot.
Reticulocyte Count
Young, newly released red blood cells - a direct gauge of bone marrow output.
Neutrophils
The most common white blood cell and the immune system's first responder to bacteria.
Lymphocytes
The white blood cells behind targeted immunity - T cells, B cells, and natural killer cells.
Monocytes
The immune system's cleanup crew - white cells that clear debris and become tissue macrophages.
Eosinophils
White blood cells central to allergic reactions and defense against parasites.
Basophils
The rarest white blood cell, involved in allergic and inflammatory responses.
Haptoglobin
A protein that binds free hemoglobin - it falls when red blood cells break down early.
Blood Type and Rh Factor
Which ABO group (A, B, AB, or O) and Rh factor (positive or negative) your red cells carry.
Metabolic Panel (BMP / CMP)
Chemistry values covering kidney function, liver enzymes, blood sugar, proteins, and electrolytes.
Glucose (blood sugar)
The amount of sugar in your blood at the moment of the draw.
Creatinine
A muscle waste product the kidneys filter out.
eGFR
A calculated estimate of how well your kidneys are filtering.
ALT
A liver enzyme that rises when liver cells are irritated.
AST
An enzyme found in the liver but also in muscle and heart.
Albumin
The main protein in blood, made by the liver.
Potassium
An electrolyte critical to heart and muscle function.
Sodium
An electrolyte that tracks your body water balance.
BUN (Blood Urea Nitrogen)
A protein waste product cleared by the kidneys, used with creatinine to assess kidney function and hydration.
Calcium
The blood level of calcium, a mineral tightly controlled by the parathyroid glands, vitamin D, and the kidneys.
Chloride
An electrolyte that partners with sodium, used to assess fluid balance and the acid-base status of the blood.
Bicarbonate
The blood's main acid buffer, reported as CO2, used to judge the body's acid-base balance.
Total Protein
The combined amount of albumin and antibody proteins in the blood, reflecting liver, kidney, and immune activity.
Bilirubin
A yellow pigment from the normal recycling of red blood cells, processed by the liver and removed in bile.
Alkaline Phosphatase
An enzyme from the liver, bile ducts, and bone, used to screen for bile flow and bone turnover activity.
GGT (Gamma-Glutamyl Transferase)
A liver and bile duct enzyme, often used to clarify where a raised alkaline phosphatase is coming from.
Lipase
An enzyme made mainly by the pancreas to digest fat, checked when the pancreas may be inflamed.
Amylase
A digestion enzyme from the pancreas and salivary glands, historically used to assess the pancreas.
LDH (Lactate Dehydrogenase)
An enzyme in almost every tissue, released into blood when cells are damaged or break down.
Ammonia
A waste product of protein breakdown that a healthy liver clears almost completely.
Kidney and Urine Tests
How well the kidneys filter, and what shows up in urine that should not.
Uric Acid
A waste product of purine breakdown, linked to gout and kidney stones and cleared by the kidneys.
Cystatin C
A small protein used to estimate kidney filtering, less swayed by muscle mass than creatinine.
Urinalysis
A broad check of urine for protein, blood, glucose, cells, and signs of infection.
Urine Albumin-to-Creatinine Ratio
Detects small amounts of the protein albumin in urine, an early marker of kidney stress.
Urine Protein
Measures protein leaking into urine, a sign of how well the kidney's filters are holding.
Urine Culture
Grows bacteria from a urine sample to confirm an infection and identify the organism.
Lipid Panel
The cholesterol and triglyceride measurements, usually ordered together.
LDL Cholesterol
The cholesterol fraction most closely tied to artery plaque.
HDL Cholesterol
The cholesterol fraction that moves cholesterol away from arteries.
Triglycerides
The main form of fat circulating in blood.
Total Cholesterol
The combined cholesterol carried in all the blood's lipoprotein particles.
Non-HDL Cholesterol
Total cholesterol minus HDL - the cholesterol in all the artery-relevant particles.
VLDL Cholesterol
Cholesterol in VLDL particles, the triglyceride carriers, usually estimated rather than measured.
Lipoprotein(a)
An inherited, LDL-like particle measured to refine long term heart risk.
Apolipoprotein B
A count of cholesterol carrying particles - one ApoB protein sits on each particle.
Thyroid Tests
Hormones and antibodies used to assess how the thyroid gland is functioning.
TSH
The pituitary signal that tells the thyroid to work harder.
Free T4
The unbound, active form of the main thyroid hormone.
Free T3
The free, active form of T3, the more potent of the two main thyroid hormones.
TPO Antibodies
Antibodies against a thyroid enzyme, used as a marker of autoimmune thyroid conditions.
Thyroglobulin Antibodies
Antibodies against thyroglobulin, the thyroid's storage protein; a marker of autoimmune activity.
Blood Sugar Tests
Measures of glucose and insulin, over a moment and over months.
Hemoglobin A1C
An average of your blood sugar over roughly the past three months.
Fasting Insulin
The pancreas hormone that moves sugar into cells, measured after an overnight fast.
C-Peptide
A by-product of insulin production, used to gauge how much insulin the pancreas makes.
Fructosamine
Sugar-coated blood proteins, reflecting average glucose over the past few weeks.
Oral Glucose Tolerance Test
Timed glucose measurements after a standard sugary drink, showing how the body handles a sugar load.
Heart Markers
Proteins released by heart muscle under strain or injury.
Troponin
A heart muscle protein released into the blood when heart cells are stressed or injured.
BNP and NT-proBNP
Hormones the heart releases when its walls are stretched, used to assess strain on the heart.
Creatine Kinase
An enzyme from muscle, released into the blood when muscle is worked hard or injured.
Homocysteine
An amino acid tied to B-vitamin status, studied as a marker of cardiovascular risk.
Clotting Tests
How quickly blood clots, and the proteins involved in making it happen.
PT and INR
Times one clotting pathway; the INR standardizes it, mainly for monitoring warfarin.
aPTT
Times a second clotting pathway, used to monitor heparin and to screen clotting factors.
D-Dimer
A fragment left over when blood clots dissolve, used mainly to help rule clots out.
Fibrinogen
The clotting protein that forms the mesh of a blood clot; it also rises with inflammation.
Hormone Tests
The chemical messengers: reproductive hormones, cortisol, and PSA.
Cortisol
The body's main stress hormone, made by the adrenal glands on a strong daily rhythm.
Testosterone
The main androgen hormone, measured for questions about energy, fertility, and hormonal balance.
Estradiol
The main form of estrogen, which changes dramatically across the menstrual cycle and with menopause.
FSH (Follicle-Stimulating Hormone)
A pituitary hormone that drives egg and sperm development; used to assess ovarian and testicular function.
LH (Luteinizing Hormone)
A pituitary hormone that triggers ovulation and drives testosterone production.
Prolactin
The milk-production hormone, which also responds readily to stress, sleep, and many common medications.
Progesterone
The hormone of the second half of the menstrual cycle, used mainly to confirm ovulation.
DHEA-S
A stable adrenal androgen used to check whether the adrenal glands are the source of excess hormones.
PSA (Prostate-Specific Antigen)
A protein made by the prostate, used in prostate health checks and cancer screening discussions.
Vitamins, Minerals and Iron
Nutrient levels and the proteins that carry and store them.
Ferritin
The protein that stores iron, used as a proxy for iron reserves.
Vitamin D
The storage form of vitamin D, used to assess vitamin D status.
Vitamin B12
A vitamin needed for nerve function and red blood cell production.
Serum Iron
The amount of iron circulating in the blood at the moment of the draw, which varies through the day.
Total Iron-Binding Capacity
How much iron the blood's carrier protein, transferrin, could hold in total.
Transferrin Saturation
The share of the blood's iron-carrying capacity that is actually filled with iron.
Folate
A B vitamin needed to make red blood cells and DNA, mostly reflecting recent dietary intake.
Magnesium
A mineral needed by nerves, muscles, and the heart; blood shows only a small slice of body stores.
Phosphate
A mineral partnered with calcium in bone, also central to how cells store and use energy.
Inflammation and Immune Markers
Non-specific inflammation tests, and the antibody tests used in autoimmune and allergy workups.
C-Reactive Protein
A general marker that inflammation is present somewhere.
Erythrocyte Sedimentation Rate
An older, slower-moving indicator of inflammation.
ANA (Antinuclear Antibodies)
Antibodies that react against the body's own cell nuclei, used as a screen for autoimmune conditions.
Rheumatoid Factor
An antibody often present in rheumatoid arthritis, though it also appears in many other settings.
Anti-CCP Antibodies
A specific antibody test used mainly when rheumatoid arthritis is being considered.
tTG-IgA
The main blood screening test for celiac disease, an immune reaction triggered by eating gluten.
Total IgE
The overall level of the antibody class involved in allergic reactions.
Celiac Genetic Test (HLA-DQ2 and DQ8)
A gene test showing whether celiac disease is genetically possible - not whether it is present.
Infection Tests
Tests for specific infections, and what positive and negative patterns generally mean.
Hepatitis B Panel
Three markers that together show hepatitis B infection, immunity from vaccination, or past exposure.
Hepatitis C Antibody
Screens for exposure to hepatitis C; a positive result is followed by an RNA test for current infection.
HIV Antigen/Antibody Test
A combined screen for HIV antibodies and the p24 viral protein, the standard first test for HIV.
H. pylori Testing
Checks for H. pylori, a stomach bacterium linked to ulcers, using breath, stool, or blood methods.
Medication Level Tests
Blood levels of medications whose dose is tuned to the individual - measured, never self-interpreted.
Therapeutic Drug Monitoring
Blood tests that check whether a medication's level sits where your prescriber intends.
Lithium Level
The amount of lithium in blood, checked regularly because its safe window is narrow.
Digoxin Level
The amount of the heart medication digoxin in blood, where the timing of the draw matters a lot.
Rapid Office Tests
The swab-and-wait tests done during a visit, and what their results generally mean.
Rapid Strep Test
A throat swab that looks for group A strep bacteria, with a result in minutes.
Rapid Influenza Test
A nose or throat swab that checks for influenza A and B, usually in under 15 minutes.
COVID-19 Tests
Antigen and PCR tests for the COVID-19 virus, trading speed against sensitivity.
Mono Spot Test
A rapid blood test for mononucleosis that detects a distinctive antibody, not the virus itself.
Vital Signs
Not lab tests, but the numbers taken at every visit - and what each one actually measures.
Blood Pressure
The force of blood against artery walls, recorded as a systolic and a diastolic pressure.
Resting Heart Rate
The number of times the heart beats each minute while the body is fully at rest.
Pulse Oximetry
The percentage of hemoglobin in the blood that is carrying oxygen, read by a light sensor on a finger.
Body Temperature
The body's core heat level, which normally varies by time of day and measurement site.
Respiratory Rate
The number of breaths taken per minute at rest, a sensitive but often overlooked vital sign.
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