CPK-MB typically returns to normal within how many hours after myocardial infarction?

• A. 24 hours
• B. 48 hours
• C. 72 hours
• D. 96 hours

Answer: (B)

CK-MB is a cardiac enzyme that rises after myocardial injury, peaks around 24 hours, and then clears from the blood relatively quickly due to its short half-life. Because of this rapid clearance, levels typically return to baseline within about 48 hours after a myocardial infarction. While some patients may still have detectable CK-MB up to 72 hours, the most consistent and commonly tested timeframe is 48 hours. This rapid normalization contrasts with troponin, which stays elevated longer and extends the diagnostic window.