Serum Creatinine Phosphokinase (CPK) – Total Activity

What Is Creatine Phosphokinase (CPK)?

Creatine Phosphokinase (CPK), also called creatine kinase, is an enzyme that plays a key role in energy production in cells. It helps convert adenosine diphosphate (ADP) into adenosine triphosphate (ATP), the body’s main energy currency. CPK exists in three main forms—CPK-MB (heart muscle), MM (skeletal muscle), and BB (brain)—but this test measures the total CPK activity in your blood.

Why Is CPK Tested?

CPK levels can rise when muscle or heart tissue is damaged, such as after a heart attack, muscle injury (e.g., from trauma, exercise, or conditions like myositis), or certain illnesses. Elevated CPK may signal muscle weakness, inflammation, or other health concerns.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The sample is sent to a lab, where CPK activity is measured using an enzymatic method. Results are reported in units per liter (U/L) or milliliters (mU/mL), though exact reference ranges vary by lab.

What Do CPK Results Mean?

Normal CPK levels can vary by age, sex, and health status. Elevated CPK may indicate muscle damage, heart issues, or other conditions. Your doctor will interpret results in relation to your symptoms and medical history.