What your kidney function reveals about your health and performance
Creatinine is a metabolic waste product produced during the energy metabolism of your muscles. More precisely, it is formed by the breakdown of creatine – the substance that serves as a rapid energy storage medium in muscle cells. Creatinine enters the bloodstream and is transported to the kidneys, where it is almost completely excreted.
The creatinine level in blood or urine is therefore an established laboratory parameter for assessing kidney function and thus an important marker for metabolic health, performance and also safety in nutritional supplements and training.
What does the creatinine level measure?
An elevated creatinine level can indicate impaired kidney function. Conversely, a very low level can also mean that there is little muscle mass, which can occur with chronic lack of exercise, malnutrition, or testosterone deficiency.
Typical normal values (serum):
- Men: 0.8 – 1.3 mg/dL
- Values may vary slightly depending on the laboratory.
- In athletic men with a lot of muscle mass – and especially when taking creatinine supplements – creatinine levels may be slightly elevated without any kidney disease being present.
To reliably assess kidney function, the creatinine level is usually calculated together with the glomerular filtration rate (GFR) , a value that indicates how well the kidney filters the blood.
Why is creatinine important for men?
An abnormal creatinine level can provide early indications of metabolic problems, dehydration, or even incipient kidney disease.
Relevant influencing factors:
- Muscles : More muscle mass = more creatinine production
- Creatine supplementation : Increases creatinine levels – without pathological significance.
- A high-protein diet can slightly raise creatinine levels.
- Dehydration : Blood concentration increases
- Medications or illnesses : Can affect kidney function
Especially in men who exercise, use many supplements or go on diets, creatinine should be checked regularly – ideally together with urea, GFR, cystatin C and electrolytes.
What symptoms should be observed in cases of elevated creatinine levels?
Slightly elevated levels without other abnormalities are often harmless – especially in athletes. It only becomes critical with a persistent elevation in combination with other symptoms , such as:
- Fatigue, decline in performance
- Fluid retention (edema)
- dark urine or reduced urine output
- Pressure sensation in the lower back
- elevated blood pressure
- Itching, skin changes (in cases of kidney failure)
Further investigation is definitely needed here - for example, through a complete kidney function test .
When and how should creatinine be measured?
Measurement is recommended at:
- Taking medications that put a strain on the kidneys
- elevated blood pressure
- known kidney disease in the family
- Symptoms such as back pain, chronic fatigue, water retention
A simple blood test for creatinine and GFR is sufficient - ideally coupled with a determination of cystatin C, as a kidney-specific laboratory value.
Conclusion
Creatinine is a significant marker for your kidney and metabolic health . Especially athletic men who experiment with diet and supplements should keep an eye on this value, not out of panic, but for early guidance.
A slightly elevated value on a single occasion is often harmless. However, if you experience symptoms, it's worth having your kidney function specifically checked.
