Understanding your creatinine levels is important for monitoring kidney function. When you go for your yearly check-up, you’ll likely have a routine blood test for creatinine. In some cases, your doctor may order a urine creatinine clearance test.
High blood creatinine levels can indicate that your body has a reduced ability to get rid of waste products — an important kidney function. Even if you feel fine, elevated blood creatinine levels may be a cause of concern.
Learn more about normal, high and low levels, when to worry about your creatine levels, and what to do about them.
[Read: How to Prevent Kidney Stones and Improve Kidney Health: Foods to Eat and Avoid]
What Is Creatinine?
Creatinine is a waste product that results from the natural breakdown of creatine, which is stored in the muscles. Creatine helps your muscles produce energy during heavy lifting or high intensity exercise.
“Creatinine can come from a variety of sources. The body can make it by itself, it can come from the diet or it can come from cell breakdown,” explains Dr. Amy Yau, a nephrologist at the Ohio State University Wexner Medical Center.
Creatinine levels are just one way of assessing how well the kidneys are working.
“We use creatinine to help us estimate kidney function because creatinine is what’s called ‘freely filtered,'” Yau explains. “It’s freely filtered by the kidney, and so we have an idea of what a normal creatinine should be in most people with intact kidney function.”
Kidney function
Your kidneys are a pair of bean-shaped organs with one located on each side of the spine, right beneath your ribcage. Kidneys are part of the urinary tract and have several system-wide functions, including:
— Filtering the blood to remove waste and excess fluid through the urine. After your kidneys filter the blood, they return vital minerals and nutrients to your body.
— Maintaining a balance of water, nutrients and minerals, such as calcium, phosphorus, sodium and potassium.
— Creating hormones that control blood pressure, develop red blood cells and keep bones strong.
“When creatinine is high, it actually means that the kidney is not doing very well,” says Dr. Ziyad Al-Aly, a clinical epidemiologist at Washington University School of Medicine in St. Louis. “It’s not really getting rid of all the toxins in the body. When creatinine is low or normal, that’s when you can think that the kidney is doing its job filtering the blood and working fine.”
Kidney disease involves a gradual loss of kidney function. As the kidneys progressively lose their filtering ability, toxic levels of fluids, minerals and waste build up in the body.
[READ: Health Questions to Ask Your Doctor]
What Causes Kidney Problems
Medical conditions and other risk factors for kidney disease include:
— Diabetes. High blood sugar can damage blood vessels and nephrons in the kidney over time.
— High blood pressure. Uncontrolled hypertension can damage arteries around the kidneys.
— Heart disease. Changes in heart function may reduce the blood supply to the kidneys.
— Smoking. Smoking decreases blood flow to the kidney.
— Inflammatory kidney conditions, such as glomerulonephritis and interstitial nephritis.
— Inherited conditions, like polycystic kidney disease.
— Ongoing urinary tract obstruction from kidney stones or an enlarged prostate. Blockages can increase pressure on the urinary tract.
— Persistent, recurring kidney infection. This is also referred to as pyelonephritis.
— Kidney cancer. Also known as kidney and renal pelvis cancer. Renal cell cancer is the most common type of kidney cancer.
— COVID-19. Long COVID causes multiple effects including blood clots that may affect small vessels in the kidneys.
— Severe dehydration. Extreme dehydration, especially chronic dehydration, results in urine that has a higher concentration of minerals, acids and waste products. Dehydration can also lead to the formation of crystals and clog the kidneys with muscle proteins. All of these things can affect kidney function and contribute to certain kidney diseases.
[Read: Surprising Signs of Gluten Intolerance.]
Signs of Kidney Disease
In the early stages, kidney disease is “silent” with few signs or symptoms, often preventing it from being detected until it’s advanced. If caught early, underlying causes of kidney disease — such as high blood pressure, diabetes, polycystic kidney disease (an inherited, chronic condition that causes fluid-filled cysts to form in the kidney) and inflammation of the glomeruli — can be treated.
Unfortunately, as a result, sometimes people will feel healthy, but in reality, the disease is very advanced. Advanced kidney damage can progress to kidney failure, which means patients may eventually require dialysis or have a kidney transplant.
In other cases, some may develop signs or symptoms that include the following:
— Swelling (edema) in the lower legs or around the eyes.
— Nausea or vomiting.
— Shortness of breath from fluid around the lungs.
— Unexplained weight loss.
— Weakness or fatigue.
— Dry, itchy skin.
— Difficulty concentrating.
— Peeing more or less than usual.
It’s important to note, however, that many of these symptoms are non-descript and not specific to kidney dysfunction.
Creatinine Blood Test
Because people rarely experience early physical symptoms of kidney disease, it’s especially important to screen for abnormal creatinine levels, which can indicate poor kidney function.
Typically, when you visit your doctor for an annual wellness visit, they’ll order a routine blood test, called a basic metabolic panel, also referred to as a BMP. If your creatinine blood test result shows elevated levels, your doctor might want more information to determine how well your kidneys are working.
You may leave the office with a homework assignment to collect your urine for the next 24 hours to provide a follow-up sample for further testing. You’ll also be asked to drink at least eight glasses of fluid during that period to provide an adequate sample to measure how effectively and efficiently your kidneys clear creatinine from your body. Hospitalized patients sometimes have a 24-hour urine collection done as part of their inpatient care.
Significantly high creatinine levels or upward trends would trigger a comprehensive diagnostic workup to determine the underlying causes.
However, creatinine levels alone don’t tell the whole story. They’re evaluated in conjunction with various other laboratory results, including estimated glomerular filtration rate and blood urea nitrogen.
Estimated glomerular filtration rate
Getting an accurate, measured glomerular filtration rate, or GFR, is an incredibly challenging process. Therefore, clinicians typically use a formula to check your GFR, which estimates how much blood passes through the glomeruli, tiny units found at the end of the kidneys that filter the blood, each minute.
“There are multiple different types of equations to estimate the GFR, which is what really tells us how well the kidney is filtering,” Yau explains. “That GFR equation is stratified based on your age. What might be a normal creatinine and reflect a normal GFR for a person who is 20 years old may be different, or a not-so-worrisome creatinine, in a person who’s 80 years old may reflect a lower GFR.”
Blood urea nitrogen
Blood urea nitrogen, or BUN, measures the amount of urea nitrogen, a waste product of protein digestion, in the blood. The protein waste is excreted by healthy kidneys. BUN is an indirect marker of kidney function, but it can be affected by other things too, like dehydration, certain medications and a high-protein diet.
Testing for BUN is often part of routine blood work; however, your doctor may also order a blood test to measure BUN levels if they suspect you have kidney disease.
Doctors take the creatinine, GFR and BUN results together to give them an idea of how the kidney is functioning.
Normal Creatinine Levels
Normal creatinine levels generally fall between 0.7 and 1.2 milligrams per deciliter. However, they aren’t exactly the same for everyone.
Certain factors affect an individual patient’s normal creatinine levels. Because creatinine is made by your skeletal muscle cells, your baseline creatinine range is affected by your size and muscle mass. Bodybuilders might have higher creatinine levels, whereas women tend to have slightly lower creatinine levels than men.
Having had amputations also affects baseline creatinine, Yau notes.
Creatinine levels should not change dramatically over time.
High Creatinine Levels
What are high creatinine levels?
While normal creatinine levels typically ranges from 0.7 and 1.2 milligrams per deciliter, no single number indicates that your creatinine levels are too high, so doctors will track your numbers over time to look for a change.
It’s important for patients not to confuse creatinine and GFR trends, Al-Aly notes. GFR works in the opposite way — a good number can go up to 100%, he says. When GFR is high that indicates good kidney function — everything’s fine. Lower GFR suggests decreased kidney function and is an indication of disease.
What causes high creatinine levels?
Factors that can elevate creatinine levels but don’t necessarily indicate kidney problems include:
— Certain conditions, like a muscle injury.
— Taking creatine supplements. Bodybuilders may take creatine supplements to help build muscle.
— High muscle mass.
— Your diet. Consuming a lot of meat can increase creatinine levels without signaling a significant kidney problem.
What are high creatinine symptoms?
High creatinine levels often indicate poor kidney function. Symptoms of high creatinine levels and kidney disfunction may include:
— Fatigue.
— Swelling.
— Changes in frequency, consistency or color of urine.
— Nausea or vomiting.
— Muscle weakness or cramping.
When should I worry about high creatinine levels?
When you have a high level of creatinine, this doesn’t always mean that your kidneys are not working well.
“We have other factors that can increase your creatinine level and it has nothing to do with your kidney function,” says Dr. Suzanne El-Sayegh, chief of nephrology at Staten Island University Hospital in New York.
It’s important to consult with your health care provider. Your provider may take into account:
— Blood or urine test results.
— Magnitude of increase in creatinine levels.
— Rate of increase of your creatinine levels.
— Severity of symptoms that are accompanying your levels.
— Any underlying conditions.
Can I improve creatinine levels on my own?
Ways to help lower your creatinine levels include:
— Maintain a balanced diet.
— Hydrate.
— Avoid creatine supplements.
— Avoid nonsteroidal anti-inflammatory drugs, or NSAIDs.
— Quit smoking.
If you’re concerned about your creatinine levels, it’s important to consult with a health care provider.
What are the treatments for high creatinine?
Treatment for high creatinine levels depends on the underlying cause and should always be individualized. Your health care provider may recommend to:
— Manage underlying health conditions, like diabetes or hypertension.
— Adjust medications if they could be affecting your kidney function.
— Make lifestyle modifications, like adding more physical activity or following a well-balanced diet.
In more severe cases, if creatinine levels are signaling advanced kidney disease, dialysis or kidney transplantation may be considered.
Any interventions or treatments should be done under the guidance of a health care professional.
Low Creatinine Levels
What are low creatinine levels?
Normal creatinine levels generally fall between 0.7 and 1.2 milligrams per deciliter. If an individual’s creatinine levels consistently fall below the lower limit of the range, it may be considered low. However, it’s important to consider low creatinine levels in the context of the individual’s overall health and medical history.
What causes low creatinine levels?
Creatinine levels might be lower in these cases:
— Pregnancy. Plasma is the largest part of your blood. If your plasma volume is increased because you’re pregnant, then your creatinine level will be falsely low.
— Vegetarianism. Sometimes vegetarians don’t have a lot of creatinine because they do not consume meat or aren’t consuming much protein.
— Muscle loss. A very thin, frail person, such as a nursing home resident who has lost a lot of muscle mass, can have extremely low creatinine levels, such as 0.2 or 0.3 milligrams per deciliter, Al-Aly says. “It’s not an indication that the kidney is doing a great job,” he points out. “It’s an indication that they don’t even have any muscle left over to even make creatinine for us to measure.”
Taking certain medications also may interfere with your levels of creatinine, such as H2 blockers taken for acid reflux (Pepcid) or some antibiotics like Bactrim, which is used to treat a variety of bacterial infections.
What are low creatinine symptoms?
Low creatinine levels do not typically cause symptoms. However, if the cause is attributed to reduced muscle function, you may experience the following symptoms:
— Fatigue.
— Muscle weakness.
— Decrease in physical strength.
— Impaired mobility or coordination.
When should I worry about low creatinine levels?
In general, below-normal creatinine levels are benign and not cause for concern. However, very low levels can be a sign of malnourishment or significant muscle mass loss.
How do I raise creatinine levels on my own?
If your creatinine levels are low enough that they are cause for concern, it’s crucial to work with a health care provider. A qualified health care provider will likely perform a thorough evaluation, taking into account your overall health and medical history, to determine if further investigation or intervention is needed.
What is the treatment for low creatinine?
Treatment for low creatinine levels primarily targets the underlying cause. For example, if levels are dangerously low due to malnourishment, treatment may involve eating a well-balanced diet with adequate amounts of protein to support muscle health.
What to Do About Abnormal Creatinine Levels
El-Sayegh emphasizes that people should not feel alarmed when they see a creatinine level that’s a little elevated or a GFR that’s a little low.
“With aging, we lose some of our kidney function, so that’s a normal process of aging,” she says.
There’s a lot you can do to improve or maintain your kidney function, such as:
— Quit smoking.
— Lose weight.
— Avoid unnecessary over-the-counter medications.
— Keep you blood pressure in check.
— Manage your blood sugar levels and pay attention to the early signs of diabetes.
— Visit your doctor regularly so they can screen you for an early diagnosis of kidney disease.
“We don’t want to wait until it’s really irreversible,” El-Sayegh says.
Once the underlying cause of decreased kidney function is determined, your health care team can develop a treatment plan to improve kidney function — such as starting medication to lower blood pressure or manage diabetes. You will likely need to see a nephrologist for disease-specific treatment if chronic kidney disease itself is the problem.
Keep in mind that creatinine levels alone aren’t enough to pinpoint a specific health condition.
“Creatinine is an imperfect marker of kidney function,” Yau says. “We use it because it’s easy, but it’s only one piece we use to look at kidney function, in general. It’s a helpful marker, it’s easy to check but it’s not the end-all and be-all.”
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Understanding Your Creatinine Levels originally appeared on usnews.com
Update 04/12/24: This story was previously published at an earlier date and has been updated with new information.
