Creatine Kinase

What is Creatine Kinase?

Creatine kinase is an enzyme found in many of the body’s tissues including the heart, brain, and skeletal muscle. It is a biomarker for muscle damage with high levels indicating a recent muscle injury.

Creatine kinase also plays a critical role in energy transport, allowing energy to be stored and then released when the body’s energy requirements increase^[1].

There are three types of creatine kinase enzymes, also called isoenzymes, found in specific tissues. They are:

1. CK-MB - heart muscle

2. CK-BB - brain tissue

3. CK-MM - skeletal muscle

Because creatine kinase is found in all muscles, if damage occurs, it will be released into the bloodstream and may indicate injury to any of these organs.

What are Normal Creatine Kinase Levels?

The NHS states that the normal creatine kinase levels are as follows:

Males	40 – 320 IU/L
Females	25 – 200 IU/L

Data collected from 2000 Forth customers shows that the average creatine kinase level is 216.7 IU/L for both sexes. This can be split into male and female groups:

Male	292.7 IU/L
Female	127 IU/L

Managing Your Creatine Kinase Levels

Creatine kinase is important for transferring phosphate from adenosine triphosphate (ATP), the main energy currency in your cells, into creatine. This chemical reaction is critical for energy storage.

So, fluctuations in creatine kinase can indicate physiological changes in the muscles, like injury or low mass.

What causes high levels?

Creatine kinase levels rise in the blood after significant muscle damage. The most common cause is strenuous exercise.

Intense exercise injures muscle tissue, resulting in the release of key muscle biomarkers, including creatine kinase, into the blood. The increase in creatine kinase is considered a natural phenomenon following exercise, with one study showing that levels rose in everyone regardless of their exercise history^[2].

Creatine kinase levels can rise by 30 times their normal value after intense exercise and can take a few days to return to normal. Although creatine kinase levels may rise after exercise, continuing to exercise can increase the risk of injury, with creatine kinase being a good indicator of overtraining.

Other causes of elevated creatine kinase include:

• Muscle injury

  recent surgery, seizures, burns, long periods of immobility

• Electrolyte imbalances

  hyponatraemia (low sodium), hypokalaemia (low potassium), hypophosphatemia (low phosphate)

• Certain medications

  statins, gout medications, beta-blockers

• Endocrine disorders

  hyperthyroidism, hypothyroidism, Cushing’s syndrome

• Muscular disorders

  rhabdomyolysis, motor neurone disease, muscular dystrophy

• Other causes

  pregnancy, Coeliac disease, heart attack, infections^[3]

Symptoms of high creatine kinase levels

The symptoms of high creatine kinase levels may be associated with the underlying cause.

One cause of high creatine kinase levels is rhabdomyolysis, a rapid breakdown of muscle fibres due to a muscle injury^[4]. The symptoms of rhabdomyolysis include:

• severe muscle aches, cramps, or pain

• dark tea or cola-coloured pee

• feeling weak or tired^[4]

If high creatine kinase levels are caused by overtraining, or exercising without adequate periods of rest, you may experience:

• Training symptoms

  muscle soreness after exercise, inability to complete your usual workouts, recovery delays, reduction in performance, heavy legs even at low-intensity

• Lifestyle-related symptoms

  fatigue, poor sleep, mood changes, depression, low energy

• Health-related symptoms

  irregular periods, weight loss, loss of appetite, diarrhoea, frequent illness or infection^[5]

What causes low levels?

Low creatine kinase levels are often associated with muscle wasting because of physical inactivity, frailty, old age, or illness.

Reduced levels are more common in older individuals because people tend to lose muscle mass as they get older.

Other potential causes for low creatine kinase levels include:

• autoimmune disorders such as lupus

• Myalgic encephalomyelitis (ME)

• pregnancy - during the 2nd trimester

• liver problems

The symptoms of low creatine kinase levels will depend on the underlying cause. If age-related muscle loss is the cause, you may experience symptoms of sarcopenia like:

• stamina loss

• slow walking

• difficulty carrying out daily tasks

• balance issues

• frequent falls

• reduction in muscle size^[7]

How to manage your creatine kinase levels

You can do several things to help keep your creatine kinase levels balanced and within a healthy range.

If your creatine kinase levels are elevated because of exercise-induced muscle damage, there are things you can do to aid your recovery:

• Rest

  Factor in sufficient rest periods into your training regime. If you are already experiencing the effects of overtraining, you may need to cut down or temporarily stop your training to help your muscles recover.

• Diet

  Review your dietary pattern to see if you have been getting enough calories, protein, vitamins and minerals to meet your energy demands. When you have finished a training session, eat foods rich in protein, carbohydrates, and healthy fats, like bananas, oatmeal, spinach, chicken, and edamame to help your muscles repair and limit damage.

• Massage therapy

  Massage is a recovery tool used by athletes to aid recovery and improve performance. Research has shown that massage can reduce stress, depression, anxiety and a reduction in pain and delayed onset muscle soreness because of lowered creatine kinase levels^[8].

It may also help to review medications because some like statins can cause muscle inflammation. If you experience muscle pain or weakness when you have started a new medication, you should inform your doctor.

Low creatine kinase levels caused by sarcopenia or immobility can often be corrected with lifestyle changes. They include:

• Exercise

  If appropriate, resistance-based strength training can improve strength and reverse muscle mass loss.

• Diet

  Following a high-quality diet can help to preserve muscle health. It’s important to incorporate protein to help build muscle mass.

Monitoring Creatine Kinase Levels

Clinically, a creatine kinase test may be requested when severe muscle trauma has occurred, such as burns, crush injuries or electrocution, as these increase the risk of developing rhabdomyolysis. Creatine kinase may also be measured after very intense exercise, immobility, a seizure, or when certain medications have been prescribed particularly statins.

Monitoring your creatine kinase levels from the comfort of your home couldn’t be easier. Creatine kinase is one of the biomarkers measured in the following Forth tests:

• Baseline
• Advanced
• Ultimate

If your creatine kinase level is slightly raised and you do not have any symptoms, it’s unlikely to be anything to worry about, especially if you are otherwise fit and healthy. You may choose to repeat your test in a few weeks to see if the levels have returned to normal. It’s also advisable to avoid strenuous exercise before collecting your sample.

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.