Blood Test Glossary

The protein in red blood cells that carries oxygen from your lungs to the rest of your body. It is the most important indicator of anemia.

Immune cells that defend the body against infection and disease. An elevated count usually signals infection or inflammation.

Tiny cells that clump together to form blood clots and stop bleeding. Critical for wound healing.

The percentage of blood volume made up of red blood cells. Closely related to hemoglobin.

Average size of red blood cells. Helps classify the type of anemia when hemoglobin is low.

The most common type of white blood cell, the first responders to bacterial infections.

White blood cells that include T-cells and B-cells — the core of adaptive immunity.

Sum of all cholesterol in the blood. High levels increase the risk of heart disease and stroke.

Often called "bad" cholesterol. LDL deposits cholesterol in artery walls, leading to plaque and cardiovascular disease.

"Good" cholesterol that transports excess cholesterol back to the liver for removal. Higher levels are protective.

Blood fats derived from dietary fat and excess calories. Elevated levels are linked to heart disease and pancreatitis.

The pituitary gland hormone that controls thyroid function. The most sensitive test for thyroid disorders.

The active, unbound form of the main thyroid hormone. Confirms thyroid dysfunction when TSH is abnormal.

The most biologically active thyroid hormone. Helps evaluate hyperthyroidism and thyroid conversion disorders.

Blood sugar level measured after an 8+ hour fast. The primary screen for diabetes and prediabetes.

Reflects average blood sugar over the past 2–3 months. The gold standard for diabetes monitoring.

Regulates fluid balance and nerve/muscle function. Critically controlled by the kidneys.

Essential for heart rhythm and muscle contraction. Even small deviations can be dangerous.

Waste product from muscle metabolism. Elevated levels indicate impaired kidney filtration.

Calculated estimate of how well kidneys filter blood per minute. The best overall kidney function test.

Liver enzyme most specific to liver damage. The primary marker for hepatitis, fatty liver, and drug-induced liver injury.

Liver enzyme also found in heart and muscle. An AST:ALT ratio > 2 suggests alcoholic liver disease.

Enzyme from liver, bile ducts, and bone. Elevated in bile duct obstruction and bone disorders.

Yellow pigment from red blood cell breakdown. High levels cause jaundice (yellow skin/eyes).

Major protein made by the liver. Reflects liver's synthetic capacity and nutritional status.

The storage form of vitamin D. Produced in skin from sunlight and obtained from food. Critical for bone health, immunity, and mood.

Essential for nerve function, DNA synthesis, and red blood cell formation. Only found naturally in animal products.

Iron storage protein. The most sensitive marker of iron deficiency before anemia develops.

B-vitamin essential for DNA synthesis and cell division. Critical during pregnancy to prevent neural tube defects.

Mineral involved in 300+ enzymatic reactions. Important for heart rhythm, muscle, nerve, and glucose metabolism.

Baseline insulin level. High fasting insulin is an early sign of insulin resistance, often before blood sugar rises.

Produced equally with insulin by the pancreas. Distinguishes Type 1 from Type 2 diabetes and evaluates insulin production.

Marker of systemic inflammation. The high-sensitivity test predicts cardiovascular risk independent of cholesterol.

Amino acid that damages blood vessel walls at high levels. Elevated by low B6, B12, and folate.

Proteins released from damaged heart muscle. The most sensitive and specific markers of heart attack.

Released by stressed heart ventricles. Key marker for diagnosing and monitoring heart failure severity.