Creatine kinase, also known as phosphocreatine kinase or creatine phosphokinase, is an enzyme or type of protein that is found in several tissue types of the human body, including the muscle and the brain. The function of this enzyme is to catalyze the conversion of creatine to phosphocreatine by applying itself in the consumption of adenosine triphosphate, the generation of adenosine diphosphate, and the reverse reaction. Adenosine triphosphate is a vital source of energy in biochemical reactions; in the skeletal muscle, the brain, and the smooth muscle - or all tissues that swiftly use up adenosine triphosphate - phosphocreatine acts as an energy reservoir for the quick regeneration of adenosine triphosphate. This is a very important function, and even though it doesn't sound like much, creatine kinase definitely has its work cut out.

Going back to basics, there are three types of creatine kinase or isoenzymes in the body: CK-BB is mainly produced by the brain and the smooth muscle; CK-MB is primarily produced by the heart muscle; and most of CK-MM is produced by the skeletal muscle.

In normal conditions, there is very little creatine kinase circulating in the blood of the average, healthy human being. Taking the creatine test is a good idea to find out where exactly it is that one stands when it comes to the prevalent level of creatine kinase in one's body. The test specifically measures the blood levels of certain muscle and brain enzyme proteins; the normal results for females range between 10 – 79 units per liter (U/L) and 17 – 148 U/L in males. A lower than normally low level of creatine kinase shows that you have been drinking excessively; alcohol liver disease and rheumatoid arthritis are two of the most common possibilities that exist with respect to lowered levels of creatine kinase.

On the other hand, if the test reveals that the level of creatine kinase circulating in the blood is higher than it should be in normal conditions, then chances are that the human body in question has suffered damage either to the muscle or the brain. In fact, astronomical levels of creatine kinase are indicative of injuries, rhabdodomyolysis, myocardial infarction, myocarditis, myositis, malignant hypethermia, McLeod syndrome, neuroleptic malignant syndrome, and hypothyroidism. If most of this sounds like gibberish to you, just remember that a heart attack, a muscle disease or a stroke may result in abnormally raised creatine kinase levels in the blood. Statin medications used to decrease serum cholesterol levels may also be the culprit.

Experts suggest that anyone who is not sure whether or not they have had a heart attack (which is hard to imagine!) or whether muscles in their bodies have been damaged as a result of any sort of activity, should make it a point to go for a creatine kinase test. This group also includes those with chest pain, muscle pain, and any sort of muscle weakness. Emergency patients (or patients with acute renal failure) are routinely taken through this test, which actually only requires one's blood sample drawn from a vein in the arm (not scary at all!).