In some cases, high creatinine levels can signal chronic kidney disease or another kidney issue.

Here’s how to know if creatinine levels are too high and how high creatinine is typically treated.

• 0.7 to 1.3 milligrams (mg) per deciliter (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. Normal creatinine levels depend on body size, muscle mass, sex, age, and hydration status. “While a creatinine level of 2 mg/dL can translate into a normal kidney function for a highly muscular, tall athlete, the same levels 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 in the blood due to higher levels of creatine breakdown, which is normal and not an indication of poor kidney function, Zuquello says.

“Abnormal creatinine levels typically reflect an issue with kidney function or muscle mass rather than being standalone symptoms,” says Fakhri Kalolwala, MD, a board-certified internal medicine physician and primary care provider at Aqeeq Internal Medicine in Houston.

• Loss of appetite
• Fatigue
• Headache
• Dry, itchy skin
• Nausea
• Unexplained weight loss

• Bloody stools
• Bad breath or a metallic taste in your mouth
• Bruising easily
• Changes in mental status or mood
• Loss of appetite
• Numbness, particularly in the hands or feet
• Fatigue
• Hand tremor
• Heart murmur
• Nausea or vomiting
• Nosebleeds
• Persistent hiccups
• Prolonged bleeding (including nosebleeds)
• High blood pressure (hypertension)
• Seizures
• Shortness of breath
• Pain between the ribs and hips
• Swelling in the legs, ankles, and feet
• Little or no urination
• Excessive urination

Consult your primary care provider (PCP) if you experience any of these symptoms, Dr. Kalolwala says. A PCP can refer you to a specialist if necessary.

But high creatinine levels don’t often come with noticeable symptoms, so it’s important to schedule primary care screenings and preventive visits regularly so your provider can diagnose underlying health conditions before they become severe, says Kalolwala.

These are the main causes of high creatinine levels.

• Kidney disease, acute kidney injury, or kidney failure High creatinine levels are typically indicative of kidney dysfunction caused by one of these health conditions, Zuquello says. When the kidneys don’t function properly, they aren’t able to filter creatinine out of the bloodstream.
• A high-protein diet or creatine supplements Creatine is broken down into creatinine. Therefore, high amounts of creatine-rich foods (protein sources such as meat and fish) or creatine supplements can lead to high levels of blood creatinine, explains Bethany Keith, RDN, a registered dietitian-nutritionist at Renal Care 360° in Atlanta. This isn’t necessarily a problem — there’s no established upper limit (the maximum amount you should consume daily) for protein or creatine in healthy people, and doses of up to 25 grams (g) per day have been used safely in research studies.

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  That said, people with kidney disease or acute kidney injury may have to limit dietary protein and avoid creatine supplements because their kidneys are unable to clear creatinine effectively. Keith suggests talking to your doctor about how much protein to aim for if you have a kidney condition.
• High muscle mass Because creatinine results from creatine breakdown during muscle synthesis, people with more muscle mass will naturally have higher creatinine levels in their blood, Zuquello says.

“Since high creatinine levels are generally associated with kidney dysfunction, all conditions that cause kidney disease can be considered as risk factors,” Zuquello says. These conditions include, per Zuquello:

• High blood pressure (hypertension)
• Heart disease
• Type 2 diabetes
• Lupus
• Prostate disease (such as prostatitis or prostate cancer)
• Overuse of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen

According to standard ranges, high creatinine is diagnosed when blood levels are higher than 1.3 mg/dL for men and 1.1 mg/dL for women. But “normal” creatinine levels vary depending on age, sex, body size, muscle mass, and hydration status, so it’s important to speak with your physician to determine if your blood creatinine levels are too high.

“Until proven otherwise, high creatinine levels suggest the presence of kidney disease,” Zuquello says, explaining that high creatinine levels aren’t treated, per se; instead, the underlying kidney disease is treated in the following ways:

• Avoid further kidney damage by managing or lowering blood pressure, cholesterol, and blood sugar.

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• Stop smoking.

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• Avoid NSAIDs.

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• Follow a low-protein diet to limit the creatine and reduce the production of creatinine.

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• Take medications, such as diuretics, which help your body eliminate excess fluid.

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Keith says no treatment is necessary if high creatinine levels are caused by eating a high-protein diet or taking creatine supplements, and there’s no evidence of kidney disease.