What It Means When Your Creatine Kinase Is Low

Creatine kinase (CK) is an enzyme in the body, found primarily in the muscles, heart, and brain. According to the Cleveland Clinic, CK plays an important role in the production of energy in the muscles and is often measured in a blood test to assess muscular diseases, function, and inflammation. There are three different forms of CK found in the body: CK-BB, CK-MB, and CK-MM. CK-BB is primarily found in the brain, CK-MB in the heart muscle, and CK-MM in the skeletal muscle, per the Cleveland Clinic.

CK is typically measured in units of enzyme activity per liter of serum, or U/L. Some people may have low or high creatine kinase levels — the normal range in the blood can vary depending on the laboratory and the method used to measure it. In general, the normal range for CK is typically considered to be between 55 and 170 U/L for men and between 30 and 145 U/L for women (via Testing.com). It's always best to consult a healthcare professional to interpret your CK levels, as what's considered normal might vary depending on factors such as age, gender, and overall health, explains Testing.com.

Low CK levels can occur for a variety of reasons and can indicate different health conditions. According to a 1998 article published in the journal Clinical Chemistry, one possible cause is low muscle mass or cachectic states. Cachectic syndrome, also known as cachexia, is associated with muscle loss with other accompanying symptoms such as inflammation, anorexia, and insulin resistance, per a 2011 article published in the Journal of Cachexia, Sarcopenia, and Muscle.

Some genetic conditions, such as myopathies, can also cause low CK levels, according to a 2009 study published in the journal Muscle & Nerve. Myopathies are a group of inherited muscle disorders that can attack the muscles causing weakness and pain, per the Cleveland Clinic.

Interestingly, another 2009 study published in the journal Clinical Autonomic Research found that low CK levels correlated with a higher incidence of fainting. 

Lastly, in a 1996 study published in the Journal of Rheumatology, low CK levels were reported in patients with inflammatory rheumatic diseases like lupus and rheumatoid arthritis. The study concluded that inflammation itself played a huge role in the reduction of CK levels.

If your blood test results indicate low CK levels, your doctor might order additional blood tests or a muscle biopsy. They might also look into other factors, such as symptoms and medical history, to determine the cause of low CK levels and make a diagnosis.

Treatment for low creatine kinase (CK) levels might also depend on the underlying cause of the low levels. If low CK levels are caused by myopathy, your doctor will determine the next steps. According to the Cleveland Clinic, physical therapy and occupational therapy are normally used to help improve muscle strength and function. Medications, such as corticosteroids, may be used to reduce inflammation and pain.

If low CK levels are caused by cachexia, there is no current treatment method, explains Healthline. According to the source, therapy is the current mode of managing the condition and includes exercise, diet changes, and appetite stimulants.