Your doctor may order a creatinine test to assess the health of your kidneys. A high creatinine level could be a sign of an issue such as chronic kidney disease (CKD).
Creatinine is a waste product that’s produced by your muscles during normal metabolism. It comes from the breakdown of a molecule called creatine, which helps supply energy to muscles. Creatine can be found in animal foods and can also be made in the body by the liver, kidneys and pancreas.
When the kidneys are functioning properly, they filter creatinine from your blood and into your urine to be excreted. But if the kidneys aren’t working well, creatinine can build up in the blood, says Radames Zuquello, MD, a nephrologist at South Carolina Nephrology and Hypertension Center in Walterboro, resulting in a high creatinine level.
Your creatinine level is measured with a blood test. A creatinine test is included on a basic metabolic panel and part of the routine blood work that is usually done at your regular physical and during hospital admission.
Healthy creatinine levels typically fall within these ranges:
0.7 to 1.3 mg/dL for men
0.6 to 1.1 mg/dL for women
By these standards, creatinine levels above 1.3 mg/dL for men and 1.1 mg/dL for women are considered high.
But Dr. Zuquello says it’s not that simple, since these standard ranges don’t necessarily apply to everyone. What's normal for a creatinine level depends on body size, muscle mass, sex, age, and hydration status. “While a creatinine level of 2 mg/dL can translate into normal kidney function for a highly muscular, tall athlete, the same level can also signify severe kidney disease in an elderly, frail, bedbound person with low muscle mass,” he says.
Similarly, someone who eats lots of meat or fish (both sources of creatine) or takes creatine supplements regularly may have slightly elevated levels of creatinine due to increased creatine breakdown, which is normal and not an indication of poor kidney function, Zuquello says.
Because the results of a creatinine test are not always easy to interpret, clinicians may refer to other kidney function tests, such as your cystatin C level. Combining your kidney test results with your age and sex provides your doctor with your estimated glomerular filtration rate (eGFR), a more comprehensive measure of kidney function. For most adults, an eGFR below 90 indicates some measure of chronic kidney disease.
High creatinine levels don’t necessarily cause noticeable symptoms, says Fakhri Kalolwala, MD, a primary care provider at Aqeeq Internal Medicine in Houston: “Abnormal creatinine levels typically reflect an issue with kidney function or muscle mass, rather than being stand-alone symptoms.”
Because chronic kidney disease is usually asymptomatic in its early stages, clinicians order creatinine tests during primary care screenings and preventive visits so your provider can diagnose CKD or other underlying conditions before they become severe, says Dr. Kalolwala.
Earlier symptoms of chronic kidney disease may include the following:
Loss of appetite
Fatigue
Headache
Dry, itchy skin
Nausea
Unexplained weight loss
At more advanced stages, as CKD progresses toward kidney failure, symptoms become more severe:
Consult your primary care provider if you experience any of these symptoms, Kalolwala says. Your doctor can refer you to a specialist if necessary.
“Until proven otherwise, high creatinine levels suggest the presence of kidney disease,” Zuquello says. Chronic kidney disease can develop in anyone and at any age, but it most often develops slowly, as a consequence of years of suboptimal metabolic health.
“Since high creatinine levels are generally associated with kidney dysfunction, all conditions that cause kidney disease can be considered as risk factors,” Zuquello says. Major risk factors for CKD include the following:
Like other noncommunicable diseases, CKD is more likely to affect people of lower socioeconomic status. People who lack access to healthy food options, quality healthcare, or safe outdoor spaces for exercise may be at a higher risk of developing CKD, as are people who are exposed to pollution, stress, discrimination, and even social isolation.
CKD can also be triggered by a number of other conditions affecting the kidneys:
Some causes of high creatinine levels are not a sign of poor kidney function and do not require treatment:
High-Protein Diet Creatine is broken down into creatinine. Therefore, high amounts of creatine-rich foods (protein sources such as meat and fish) can lead to high levels of blood creatinine, says Bethany Keith, RDN, a registered dietitian-nutritionist at Renal Care 360 in Atlanta.
Creatine Supplements Consuming creatine supplements, a popular choice for athletes and bodybuilders, can similarly raise blood creatinine levels, according to Keith.
High Muscle Mass Because creatinine results from creatine breakdown during muscle metabolism, people with more muscle mass will naturally have higher creatinine levels in their blood, Zuquello says.
High creatinine levels aren’t a direct treatment target; instead, the underlying kidney disease must be addressed. Doing so typically requires a comprehensive approach, including new medications and healthy habits:
Make lifestyle changes, particularly eating a healthier diet and increasing physical activity, to help lower blood pressure, cholesterol, and blood sugar, all of which reduce stress on the kidneys.
Stop smoking.
Avoid nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin), naproxen (Aleve, Naprosyn), celecoxib (Celebrex), indomethacin (Indocin), ketorolac (Toradol), and meloxicam (Mobic).
Limit your protein and salt intake, and possibly your intake of other minerals such as potassium and phosphorus, if told to do so by your clinician.
Use prescription drugs as recommended by your doctor. Examples may include diuretics, which help your body eliminate excess fluid, or antihypertensive agents to bring your blood pressure down.
If your kidney disease has an independent underlying cause, such lupus or an infection, it will also be critical to treat that condition.
Early intervention is critical. After kidney disease has progressed to its most severe level, the only treatments are dialysis or a kidney transplant.
Keith says that no treatment is necessary if high creatinine levels are caused by high muscle mass or by eating a high-protein diet or taking creatine supplements, though your doctor may first want to confirm that there’s no evidence that you have kidney disease.
Creatinine levels are measured with a blood test and used to gauge kidney function.
A high creatinine level may indicate that your kidneys aren’t working as well as they should, a possible sign of chronic kidney disease.
Some people — including very muscular individuals, those who eat a large amount of protein, and those who take creatine supplements — may have high creatinine levels that are not a sign of poor kidney function and do not require treatment.
Creatinine test results can be difficult to interpret. If a blood test shows that your creatinine level is high, it’s best to follow up with your doctor.
