This test is most often used to judge high, rather than low creatinine levels in the body and is likely to be used alongside other tests to look at overall kidney health. Levels of creatinine are often linked with muscle mass or the amount of muscle in the body, which can decrease with age or illness.
Low levels may indicate that muscles are less strong or are deteriorating, for example with a disease such as muscular dystrophy MD. Older adults often lose some muscle mass with age, and this is not usually a serious medical concern. Creatine is made in the liver, and an unhealthy liver that is not working properly will not be able to make the normal amount of creatine.
For chronic liver disease, there can be a 50 percent reduction in the production of creatine. This means that there will be lower levels of creatinine in the blood, which can be checked with a simple blood test called a serum creatinine test.
Although creatine is made naturally in the body, a small amount comes from food, so low levels of creatinine could relate to diet. Creatine is mostly found in meat, so those who follow a vegetarian or low-protein diet are likely to have lower levels than people who eat meat. A prolonged period of not eating, or having an illness that prevents someone from eating, could be another cause of low levels of creatinine. Pregnancy is often a cause of low creatinine levels, which should return to normal after a woman has given birth.
In the majority of cases, symptoms are unlikely to point clearly to low creatinine levels and could indicate other health problems. A medical professional will test creatinine levels as part of a diagnosis if other symptoms are present, and a test is needed.
Usually, low creatinine means that there is too little creatine being produced in the body. This state will relate to the liver, muscles, or diet.
High levels of creatinine usually mean that there is too much creatine in the body, or that creatinine is not being filtered and removed from the body properly. Creatinine levels often rise during intense exercise, as more creatine is burned for energy, or because someone may eat a high-protein diet.
High levels could also indicate a problem with the kidneys, as these organs get rid of waste products from the body to keep the blood clean.
Low creatinine levels may indicate various different conditions, so a doctor will use test results alongside other checks to work out what the underlying issue could be. For a creatinine urine test, you may need to collect urine over 24 hours in containers provided by the clinic.
For either test, you may need to avoid eating meat for a certain period before the test. If you take a creatine supplement, you'll likely need to stop use. For a serum creatinine test, a member of your health care team takes a blood sample by inserting a needle into a vein in your arm. Results from creatinine in blood or urine are measured and interpreted in many ways, including the following:.
Creatinine usually enters your bloodstream and is filtered from the bloodstream at a generally constant rate. The amount of creatinine in your blood should be relatively stable. An increased level of creatinine may be a sign of poor kidney function. The typical range for serum creatinine is:. The measure of serum creatinine may also be used to estimate how quickly the kidneys filter blood glomerular filtration rate.
Because of variability in serum creatinine from one person to another, the GFR may provide a more accurate reading on kidney function. The formula for calculating GFR takes into account the serum creatinine count and other factors, such as age and sex.
Fat and protein breakdown -- primarily from muscle tissue -- provides needed energy with low calorie intake or absorption. Prolonged starvation or illness that reduces nutrient absorption can lead to significant loss of muscle mass and a low creatinine level.
Diet can also impact creatinine level. A vegetarian diet is one common cause of a low creatinine. Animal protein from meat and fish contributes to the blood creatinine level, but plant-based foods do not. Since vegetarians do not eat animal proteins, their creatinine levels tend to be lower than those of nonvegetarians.
Pregnant women also tend to have a reduced blood creatinine level. This occurs, in part, because the kidneys more efficiently clear creatinine and other waste products from the blood during pregnancy. Advanced liver disease is another possible cause of low creatinine. Creatinine is an indicator of kidney function.
In this article, we discuss how it is produced, disposed of, as well as why it is an important indicator of kidney disease or reduced kidney function.
Creatinine is a waste product created from the normal wear and tear of muscles [ 1 ]. It is produced from creatine , a protein needed to generate the energy for muscle contractions [ 2 ]. The consumption of cooked meat can also introduce it to the body. Creatinine production essentially reflects lean body mass, and because this mass changes little from day to day, the production rate is also fairly constant.
Women, children, and older people tend to have lower levels of creatinine compared to adult men because they have less muscle mass [ 1 ]. Creatinine is removed from the body by the kidneys, which filter almost all of it from the blood into the urine. That is why blood levels are usually a good indicator of how well your kidneys are working [ 3 , 1 ]. Creatinine levels can be tested in isolation, or as a part of your basic metabolic panel BMP or your comprehensive metabolic panel CMP.
Kidneys are the organs that filter the blood and remove toxic substances and excess water. This filtering cleans the blood and maintains a constant stable environment in the body homeostasis [ 4 ]. Creatinine, like other waste molecules, enters the kidneys and gets filtered in specialized compartments glomeruli. After filtering, it is discarded in the urine [ 4 ]. Kidney function can be estimated by measuring the creatinine clearance inconvenient or by looking at creatinine levels in the blood easier and more affordable [ 5 ].
The most direct method for measuring creatinine clearance is the collection of urine samples for a time period of 24 hours and a blood sample. Alternatively, a formula that uses the blood levels of creatinine, age, weight, and gender can also be used to calculate clearance [ 5 ].
Despite the method of calculation used, the value of creatinine clearance shows how much gets removed from the blood by the kidneys and this provides an estimate of kidney function [ 5 ]. Although creatinine clearance provides one of the most direct and cost-free methods to estimate kidney function, its measurement has several disadvantages [ 6 , 7 ]:.
However, although high creatinine levels in the blood are often associated with reduced kidney function, other factors can also increase or decrease creatinine levels.
For a couple of decades now, eGFR or estimated glomerular filtration rate, is routinely calculated based on creatinine levels.
Creatinine levels increase with muscle mass. Other factors, such as age, sex, ethnicity, diet, etc. Levels may vary slightly between labs, due to differences in equipment, techniques, and chemicals used. Your doctor will interpret your results in conjunction with your medical history and other test results, such as glomerular filtration rate eGFR , blood urea nitrogen BUN , phosphate, calcium , sodium, potassium, and glucose.
As the kidneys become impaired for any reason, they start having troubles filtering out waste products and toxins.
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