What is the Creatine Kinase (MB Fraction) test?

The Creatine Kinase MB (CK-MB) test measures the MB isoenzyme of creatine kinase, an enzyme found predominantly in cardiac muscle cells. When heart muscle is damaged, CK-MB is released into the bloodstream.

CK-MB testing has traditionally been used in the assessment of myocardial injury, including suspected heart attacks and other conditions affecting the heart muscle.

Although high-sensitivity troponins are now widely used, CK-MB remains valuable in certain clinical scenarios, such as detecting reinfarction or assessing muscle injury patterns.

This test is commonly requested in cardiology and emergency medicine as part of a broader cardiac evaluation.

Why do I need a CK-MB test?

CK-MB testing helps determine whether symptoms may be related to heart muscle damage rather than skeletal muscle injury.

You may need a CK-MB test if you:

• Have chest pain or pressure
• Experience shortness of breath
• Have suspected myocardial injury
• Are being monitored after a heart attack
• Have abnormal ECG findings
• Have unexplained elevated total CK levels
• Require assessment of cardiac vs skeletal muscle damage

Symptoms that may prompt testing include:

• Chest discomfort
• Radiating arm, jaw, or back pain
• Palpitations
• Dizziness
• Fatigue
• Nausea or sweating

Benefits of the CK-MB test

• Supports assessment of heart muscle injury
  Helps identify cardiac-specific enzyme release.
• Distinguishes cardiac from skeletal muscle damage
  Useful when total CK is elevated.
• Assists in monitoring reinfarction
  CK-MB can rise again after repeat injury.
• Clinically recognised cardiac marker
  Long-established use in cardiology.
• Useful in acute and follow-up testing
  Supports dynamic monitoring.
• Simple blood test
  Requires only a single blood sample.
• Complements other cardiac markers
  Used alongside troponins when indicated.
• Supports clinical decision-making
  Helps guide further cardiac investigations.

Step by step – how the test works

You can access CK-MB testing UK-wide through two options:

1. Clinic appointment
   Attend your nearest UK clinic, where a healthcare professional will take your blood sample.
2. At-home or hotel visit (£60 extra)
   A qualified phlebotomist comes to your home or hotel, so you don’t need to travel.

Your sample is analysed in an accredited UK laboratory, and results are delivered securely.

Your results explained

Low or normal CK-MB levels

Suggest no evidence of recent heart muscle injury.

Typical UK reference range:

• < 5 ng/mL (laboratory dependent)

Mildly elevated CK-MB levels

May indicate minor cardiac injury or non-cardiac causes; clinical correlation is required.

Typical UK interpretation:

• Slightly above reference range

High CK-MB levels

Suggest significant cardiac muscle damage, particularly when associated with symptoms and ECG changes.

Typical UK interpretation:

• Clearly above reference range

Reference ranges vary between laboratories and results must be interpreted clinically.