The creatinine blood test measures the level of creatinine in the blood. The result of this blood test is useful, as it is an important marker of how well the kidneys are working.
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.
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.
A doctor or a healthcare professional will carry out the blood test.
Before the test, they might ask questions related to:
It is best to discuss any medical conditions and any family history of kidney disease at the time of the blood test.
There is no need to avoid food or drink before the blood test.
The blood test involves collecting blood from a vein in the arm or hand. The doctor then sends the sample to a lab for analysis.
The kidneys are responsible for keeping the level of creatinine in the blood within a normal range.
The typical reference range for serum creatinine is 60 to 110 micromoles per liter (mmol/L) (0.7 to 1.2 milligrams per deciliter (mg/dL)) for men and 45 to 90 mmol/L (0.5 to 1.0 mg/dL) for women.
Some of the causes of high creatinine levels are:
Chronic kidney disease
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.
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.
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.
Creatine is present in the muscles and helps them produce energy. Rigorous exercise can increase creatinine levels by increasing muscle breakdown.
Antibiotics, such as trimethoprim, and H2 blockers, such as cimetidine, can cause a temporary increase in measured serum creatinine levels.
Creatinine levels may be lower than normal for the following reasons:
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 gravisor 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.
Weight loss can result in the reduction of muscle mass, leading to low levels of creatinine.