Creatine Kinase

What it is

Creatine kinase (CK), also known as creatine phosphokinase (CPK), is an enzyme found mainly in your muscles, but also in your brain and heart. Enzymes are proteins that help speed up chemical reactions in your body. CK plays a vital role in energy production within muscle cells. When muscle cells are damaged or stressed, CK is released into the bloodstream. A blood test can measure the amount of CK in your body.

In the UK, a typical reference range for CK in adults is between 40 and 320 U/l (units per litre). However, it's important to remember that this range can vary slightly between different laboratories.

Why it matters

The level of CK in your blood can give your doctor clues about the health of your muscles. If your muscle cells are healthy and intact, you'll have a lower level of CK circulating in your blood. When muscles are injured, inflamed, or overworked, they release more CK into the bloodstream, leading to higher levels.

Therefore, a raised CK level can indicate that there's been some damage to your muscle tissue. This damage could be due to a variety of reasons, ranging from strenuous exercise to underlying medical conditions. Conversely, very low levels of CK are generally not a cause for concern and are often not specifically investigated.

What can cause it to be high or low

Several factors can lead to an increase in your CK levels.

Common causes of high CK:

• Strenuous exercise: Intense physical activity, especially activities that involve a lot of muscle exertion like weightlifting, running, or cycling, can cause temporary muscle damage and therefore a rise in CK. This is often referred to as exercise-induced rhabdomyolysis.
• Muscle injury: Direct trauma to muscles, such as from a fall, accident, or even a deep intramuscular injection, can elevate CK levels.
• Muscle inflammation (myositis): Conditions like polymyositis or dermatomyositis cause inflammation of the muscles, leading to their breakdown and release of CK.
• Muscle diseases (muscular dystrophies): Inherited conditions that cause progressive muscle weakness and degeneration, such as Duchenne muscular dystrophy, are often associated with significantly elevated CK levels.
• Heart attack: Damage to heart muscle cells during a heart attack can also release CK into the bloodstream. Specific types of CK (CK-MB) are particularly indicative of heart muscle damage, though other markers are now more commonly used for diagnosing heart attacks.
• Certain medications: Some medications, particularly statins used to lower cholesterol, can rarely cause muscle inflammation and damage, leading to increased CK.
• Alcohol abuse: Chronic heavy alcohol consumption can be toxic to muscle tissue.
• Other medical conditions: Conditions like hypothyroidism (underactive thyroid), seizures, and certain infections can sometimes be associated with higher CK levels.

Low CK levels are generally not considered clinically significant and usually don't require further investigation.

Lifestyle factors that may help

For individuals experiencing elevated CK levels, particularly those related to muscle strain or overexertion, certain lifestyle adjustments might be helpful to discuss with a healthcare professional.

• Gradual increase in exercise intensity: If you're starting a new exercise routine or increasing the intensity of your current one, doing so gradually can help your muscles adapt and minimise damage.
• Adequate rest and recovery: Allowing your muscles sufficient time to recover between strenuous workouts is important. This includes getting enough sleep.
• Hydration: Staying well-hydrated, especially during and after exercise, is crucial for overall muscle function and recovery.
• Balanced diet: Ensuring your diet provides the necessary nutrients for muscle health can support muscle repair and function.

Questions to discuss with your GP

If your CK levels are found to be high, or if you are experiencing symptoms that concern you, it's a good idea to have a conversation with your GP. Here are some questions you might consider asking:

• What might be causing my CK level to be high?
• Are my CK levels significantly high, and what does this mean for my health?
• Could my current medications or any recent changes in my health be affecting my CK levels?
• Are there any specific lifestyle changes you would recommend for me based on my CK results?
• Do I need any further tests to investigate the cause of my elevated CK levels?
• What is the normal range for CK, and how do my results compare?