Creatinine
Creatinine is a term that often crops up in medicine, especially when it comes to the kidneys. But what exactly is creatinine, why is it so important and how is it measured in laboratory medicine in Germany?
What is creatinine?
Creatinine is a molecular waste product that is produced naturally in the body. It is formed when the muscles work. More precisely, it is formed from creatine, a substance that supplies the muscles with energy. Creatine is used up during exercise or sport, and creatinine remains as a “by-product”. This substance no longer has a function in the body and is transported to the kidneys via the blood. The kidneys filter the creatinine from the blood and then excrete it in the urine. This makes creatinine a perfect indicator of how well the kidneys are working.
Why is creatinine important?
In Germany, as elsewhere, doctors use the creatinine level to check kidney function. If the kidneys are healthy, they keep the creatinine level in the blood low because they excrete the substance efficiently. However, if the kidneys are damaged – for example due to chronic kidney disease, diabetes or high blood pressure – the creatinine can no longer be filtered properly. It accumulates in the blood and the level rises. A high creatinine value is therefore a warning signal that something is wrong with the kidneys. At the same time, a very low value can indicate low muscle mass, for example in older people or in the case of malnutrition.
How is the creatinine value determined?
In Germany, the creatinine value is usually measured as part of a blood test. This is done in laboratory medicine, a field that deals with the analysis of blood, urine and other body fluids. To determine this, a doctor takes a small amount of blood from the patient, usually from a vein in the arm. This blood is then sent to the laboratory.
There are various methods for measuring creatinine levels in the laboratory. The most common is the so-called “Jaffé method“. This involves triggering a chemical reaction: creatinine in the blood reacts with a special substance and changes its color. A device then measures how much the color has changed and the creatinine value is calculated from this. A more modern and precise method is enzymatic determination, in which enzymes are used to recognize the creatinine. This method is often used in Germany because it is less disturbed by other substances in the blood.
The value is usually given in milligrams per deciliter (mg/dl) or micromoles per liter (µmol/l). In Germany, the normal values for adults are usually between 0.7 and 1.2 mg/dl for men and 0.5 to 1.0 mg/dl for women. Children and older people may have different values because muscle mass and kidney function change with age.
What happens to the results?
Once the creatinine value has been determined, the doctor will look at the result. He will often also calculate the so-called “glomerular filtration rate” (GFR). The GFR shows even more precisely how well the kidneys are filtering and uses the creatinine value, age, gender and sometimes the height of the patient. In Germany, this is a standard procedure for the early detection of kidney disease.
If the value is too high, the doctor may order further tests, such as an ultrasound examination of the kidneys or a urine sample. Lifestyle is also often discussed: Drinking plenty of fluids, a balanced diet and regular exercise can support the kidneys. If the values are very high or the kidneys are weak, treatment may be necessary, for example with medication or, in the worst case, dialysis.
Conclusion
Creatinine is a small substance with great significance. In Germany, laboratory medicine helps to determine creatinine levels quickly and accurately in order to keep an eye on kidney health. A normal value shows that everything is in order, while an abnormal value can be an important indication for doctors to take a closer look. Measuring creatinine thus helps to detect diseases early and protect health – simply but effectively.
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