Creatinine blood test: Purpose, procedure, and low or high ranges

Creatinine is the waste product of creatine, which the muscles use to make energy. Typically, creatinine travels in the blood to the kidneys where it leaves the body in the urine. High levels in the blood might indicate that the kidneys are not working correctly.

The creatinine blood test helps doctors to diagnose kidney disease. A poorly functioning kidney cannot filter creatinine as well as it usually does, which causes levels in the blood to rise.

What is the purpose of the test?

The body produces creatinine at a steady rate, and measuring the levels only requires a routine blood sample.

Measuring creatinine levels is an excellent way to identify the glomerular filtration rate (GFR), which is an indicator of overall kidney function.

People experience very few signs and symptoms of chronic kidney disease, so monitoring creatinine levels is crucial.

When kidneys are damaged, they have trouble removing creatinine from the blood and levels rise.

Doctors use the result of the creatinine blood test to calculate GFR, which is a more specific measure that can indicate chronic kidney disease.

A GFR of 60 or over is considered normal, a GFR less than 60 may indicate kidney disease. A level of 15 or less is defined medically as kidney failure.

Kidney obstruction

A blockage in the flow of urine, such as an enlarged prostate or kidney stone, could cause kidney obstruction. This blockage can create a backup of urine into the kidney and impair the kidney’s ability to function correctly, which might raise the level of creatinine. The medical term for this condition is hydronephrosis.


Severe dehydration is a risk factor for kidney injury, which will affect creatinine levels.

Increased consumption of protein

What a person eats can have a significant impact on creatinine levels. For example, proteins and cooked meat contain creatinine, so eating more than the recommended amount of meat or other proteins for your activity levels, or adding extra protein to the diet through supplements can cause high creatinine levels.

Intense exercise

Creatine is present in the muscles and helps them produce energy. Rigorous exercise can increase creatinine levels by increasing muscle breakdown.

Certain medications

Antibiotics, such as trimethoprim, and H2 blockers, such as cimetidine, can cause a temporary increase in measured serum creatinine levels.

Causes for low levels

Creatinine levels may be lower than normal for the following reasons:

Low muscle mass

Because the breakdown of muscle produces creatinine, low muscle mass can result in low levels of creatinine.

Older people are more at risk as muscle mass declines with age. Malnutrition can also cause low muscle mass and low creatinine levels.

Chronic conditions, such as myasthenia gravis or muscular dystrophy, may result in low creatinine levels.


Pregnancy causes an increase in blood flow to the kidney leading to increased urine production and faster elimination of creatinine, leading to lower levels.

Extreme weight loss

Weight loss can result in the reduction of muscle mass, leading to low levels of creatinine.


Dietary choices and physical activity play an essential role in regulating blood creatinine levels. It is advisable to keep protein consumption within the recommended range for age and activity level.

Talk to a doctor about the treatment options, especially if the level of creatinine in the blood is high. If it persists at a high level, people may need to see a kidney specialist. Early treatment of rising creatinine levels is essential to prevent more significant kidney disease.

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