Creatine kinase is an important enzyme needed for energy production and muscle function. Athletes have more of this enzyme in their blood, but so do obese and overweight people. High levels can tell us if there is muscle, heart, or brain damage. Keep reading to learn more about this enzyme, what it means if your levels are high or low, and how to address irregular values.
What is Creatine Kinase?
Creatine kinase (CK), also known as creatine phosphokinase, is an enzyme that plays a role in energy production. Higher amounts of this enzyme are found in tissues that use a lot of energy, such as the muscles (including the heart) and the brain [1].
Creatine kinase will leak into the blood when these tissues are damaged. That’s why blood levels of this enzyme can tell us whether there has been tissue damage, i.e. a heart attack, stroke, sports injury, or muscle disease [1, 2].
If your creatine kinase levels are high, your doctor may order a creatine kinase isoenzyme tests to determine which type of creatine kinase enzyme is high [1, 2]:
- CK-MM: muscles
- CK-MB: heart
- CK-BB: brain
Normal Range
There is still no universally agreed upon range for creatine kinase. Different laboratories have different normal ranges, reported in U/L (units per liter) or ukat/L (microkatals per liter).
People who have greater muscle mass have higher CK levels. That is why men usually have higher CK values than women.
The low normal limit for both men and women is approximately 20 – 30 U/L (0.34 – 0.51 ukat/L). The upper normal limit for men is anywhere from 200 to 395 U/L (3.4 – 6.8 ukat/L) and for women, it’s up to 207 U/L (3.52 ukat/L) [3, 4, 5].
CK levels are around 70% higher in healthy African Americans, compared to people of European descent! Some studies indicate that healthy black men and women can have significantly higher values than the currently recognized normal range(s) – up to 712 and 323 IU/L, respectively [5, 6, 7].
High Creatine Kinase Levels
Elevated CK points to recent tissue damage. However, it doesn’t point to a cause or the location of the damage.
It is possible to be healthy and have higher CK levels. As mentioned above, people of African descent can have up to 70% higher CK levels than healthy Caucasians [6, 5, 7].
Your doctor will interpret this test, taking into account your medical history and other test results, and will repeat it if necessary.
Furthermore, a “falsely high CK” due to exercise or other strenuous physical activity is very common. In a large community study of over 12,000 people in Norway, people who had elevated CK levels were re-tested after 3 days of rest. CK levels returned back to normal in 70% of the cases [8].
To ascertain that the rise in CK is due solely to exercise or exclude physical activity as a factor, the test should be repeated after a week of rest (i.e. 7 days without exercise).
If elevated CK persists, it is more likely to be due to an underlying health issue. People who have elevated creatine kinase due to an underlying health issue may experience the following symptoms [9]:
- Muscle weakness
- Cramps
- Muscle pain
- Fatigue
- Inability to exercise (due to pain or weakness)
- Dark urine
Causes of High Creatine Kinase Levels
Causes shown below are commonly associated with elevated creatine kinase. Work with your doctor or another health care professional to get an accurate diagnosis.
1) Exercise/Training
Exercise and training are the main cause of increased creatine kinase levels [10, 11, 12].
CK levels transiently increase to over 30 times the upper normal limit within 24 hours of strenuous physical activity and then slowly decline back to normal over the next 7 days. To what degree CK spikes depends on the type and duration of exercise [8, 13, 14, 15].
Studies have shown that even stretching can increase CK [16]!
Also, people who are untrained will experience greater spikes in CK levels due to greater muscle damage [8].
On the other hand, athletes have higher resting CK levels compared to non-athletes. A study of over 700 athletes suggests that normal reference ranges for athletes may be over two times higher than normal ranges: 82 – 1,083 U/L in men and 47 – 513 U/L in women [12].
Fun fact: The highest creatine kinase on record was over a million and was caused solely by a heavy workout [17]!
2) Obesity
Although higher CK levels are found in athletes, conversely, high CK levels are also found in obese and overweight people.
In a study of 1,444 subjects, higher CK levels were linked with higher BMI and waist-to-hip ratio [18].
In another study of over 10,000 adults, overweight and obese men had almost 2 times greater odds of having elevated CK [19].
Similarly, in 4,500 people, CK levels were higher in people with greater body mass [4].
Scientists may have found an explanation for this. They discovered that obese and overweight people have more fast-twitch (type II) muscle fibers and less slow-twitch (type I) muscle fibers. Fast-twitch muscle fibers have higher CK activity [4].
3) Underlying Health Issues
Creatine kinase will increase with muscle, heart, or brain damage – these can be caused by an underlying disease or disorder, including:
- Muscle injuries, physical trauma, and burns [20, 21, 22, 23, 24]
- Genetic muscle disorder, such as muscular dystrophy (i.e Duchenne muscular dystrophy) [25, 26]
- Infections by viruses, bacteria, fungi, or parasites, causing muscle wasting [27, 28, 29, 30]
- Fever, accompanied by shivering [31]
- Hypothermia, a dangerous drop in body temperature [32]
- Hormonal disorders, such as hypothyroidism, Addison’s disease, acromegaly (a disorder where the pituitary gland produces too much growth hormones), and Conn’s syndrome/hyperaldosteronism (a condition where too much aldosterone is produced in the adrenal glands) [33, 34, 35, 36, 37, 38, 39]
- Metabolic disturbances such as hyponatremia (low sodium), hypokalemia (low potassium), or hypophosphatemia (low phosphate) [8, 40, 41, 42, 43]
- Diabetes; when it causes muscle dysfunction (myopathy) [44]
- Some cases of autoimmune diseases when there is muscle involvement, such as lupus, rheumatoid arthritis, and celiac disease [45, 46, 47]
- Heart attacks [1, 48, 49]
- Head/brain injury [50, 51, 52]
- Seizures [53, 54]
- Some cancers [55, 56]
4) Medical Interventions
Interventions that damage tissues, such as injections into the muscles or any type of surgery, will increase CK levels [8, 57, 58].
5) Drugs and Toxins
Cocaine increases CK levels [59, 60, 61].
Some pharmaceutical drugs also have the potential to increase CK:
- Statins, the cholesterol-lowering drugs. In fact, muscle symptoms are the most frequent side effect of statin therapy [62, 63, 64]
- Fibrates, another group of drugs that decrease cholesterol [8, 65]
- Beta-blockers and angiotensin II receptor blockers used to decrease blood pressure [66, 8, 67]
- Glucocorticoids used to decrease inflammation [68]
- Antipsychotics [69]
- Antibiotics, antiretrovirals, and antimalarials [70, 71, 72, 8, 73]
- Isotretinoin, an acne medication [74]
- Colchicine, used to prevent gout [75]
- Chemotherapy drugs [76]
Finally, toxins like snake venom or carbon monoxide can increase CK levels [77, 78].
Health Effects of High Creatine Kinase Level
1) May Be Linked to Lower Inflammation
A study with over 12,000 people found that higher CK was linked to lower hs-CRP, which is a measure of chronic inflammation [79].
The same association was found in another study of 454 overweight and obese people [80].
2) May Prevent Blood Clotting
High plasma CK, even in the normal range, may decrease the ability of our blood to clot properly. This is especially the case after exercise when CK levels spike [81].
Decreasing Creatine Kinase
Elevated creatine kinase can be a sign of serious tissue damage or an underlying disease or disorder. The most important thing is to work with your doctor to find out what’s causing your elevated creatine kinase and to treat any underlying condition!
Refrain from strenuous exercise before testing. It causes muscle damage and increases CK levels [10, 11, 12].
Discuss the lifestyle changes listed below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!
1) Improve Muscle Recovery
If your CK gets high because your muscles get damaged after exercise, there are some steps you can take to improve muscle recovery.
Studies suggest that after strenuous exercise, an increase in creatine kinase (muscle damage) can be attenuated by consuming enough carbs, protein, and antioxidants [82].
A small study with 14 men showed that sports massage 2 hours after exercise decrease CK levels [83].
A meta-analysis of 14 studies concluded that light therapy (low-level laser therapy and/or light-emitting diode therapy) had beneficial effects on decreasing CK levels after exercise [84].
2) Lose Weight If Overweight
Lose some weight if you are overweight. People with higher BMI and weight have increased creatine kinase levels [4, 18].
Low Creatine Kinase Levels
Causes of Low Creatine Kinase Levels
1) Low Muscle Mass
The most common cause of low creatine kinase levels is muscle wasting (muscle atrophy) due to physical inactivity, illnesses, or old age [85].
2) Inflammation in Autoimmune Disease
Creatine kinase levels can be significantly reduced in autoimmune diseases, such as lupus and rheumatoid arthritis [86, 87, 88, 89]. The more inflammation there is, the lower creatine kinase levels can get.
3) Pregnancy
Total creatine kinase levels are reduced in the second trimester of pregnancy. However, they increase in late pregnancy [90].
Health Effects of Low Creatine Kinase Levels
1) Are Linked to Fainting
Studies suggest that the more creatine kinase a person has within the normal range, the better their heart and muscles can function. In a study of 442 people, people with low creatine kinase levels were 73% more likely to faint [91].
2) Increase Risk of Death
Because creatine kinase is a measure of muscle mass, it is not surprising that a link was found between low creatine kinase levels and higher mortality. Critically ill people who are weaker (with less muscle mass) have a higher risk of dying [92].
In two studies with over 1.8k patients each, critically ill and chronic kidney disease patients with low creatine kinase levels had higher mortality rates [93, 94].
Increasing Creatine Kinase
The most important thing is to work with your doctor to find out what’s causing your low creatine kinase and to treat any underlying condition!
Discuss the lifestyle changes listed below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!
1) Exercise
Exercise and physical activity, in general, build muscle and thereby increase creatine kinase levels. Most athletes have high CK levels [11, 85].
2) Protein-Sufficient Diet and Muscle-Building Supplements
Make sure your diet has enough protein to sustain your health and your level of physical activity.
A study suggests that creatine supplementation may help build muscle and increase creatine kinase activity in athletes [95].
Remember, always speak to your doctor before taking any supplements, because they may interfere with your health condition or your treatment/medications!
