By Colleen Doherty, MD 

Updated on December 17, 2023

 Medically reviewed by Steffini Stalos, DO

Creatinine is a natural waste product that accumulates in the bloodstream after a person uses their muscles. Healthy kidneys (bean-shaped organs) filter creatinine out of the bloodstream, removing it from the body in urine.

Creatinine levels provide beneficial clues about kidney function and can be measured in the blood or urine. A high blood creatinine level and low urine creatinine level is often a sign of kidney injury or disease.

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This article defines a healthy creatinine level in adults and reviews the causes (including non-kidney-ones) of an abnormal creatinine level. Possible symptoms of high creatinine in the bloodstream are also discussed.

Creatinine in the Pediatric Population

Like adults, creatinine levels are a valuable marker of kidney function in the pediatric population. However, the creatinine reference range differs from adults because, in babies and children, creatinine gradually increases with age as they gain more muscle mass (weight).¹

Creatinine: What Levels Are Above Average?

A "normal" or "average" creatinine level is difficult to define precisely because levels are influenced by various factors, namely age, sex, muscle weight, activity, nutritional status, and chronic illnesses.²

For example, since creatinine is proportionate to muscle mass, older adults commonly have lower creatinine levels due to reduced muscle mass.³

Likewise, creatine is present in organs and muscles of animals, so a high consumption of cooked meats increases creatinine levels.

Lastly, the reference range for creatinine values may vary slightly among laboratories. Always speak with a healthcare provider about individual test results.⁴

Average Blood Creatinine

In adults with healthy kidney function, a healthy blood creatinine level for males is between 0.7 to 1.3 milligrams per deciliter (mg/dL), and for females is between 0.5 and 1.1 mg/dL.⁵ The terms for sex or gender from the cited source are used.

High Blood Creatinine

A high blood creatinine level may indicate kidney injury or disease.⁶

To evaluate kidney function, a healthcare provider uses the blood creatinine level to calculate a person's estimated glomerular filtration rate (eGFR).

The eGFR is a formula that approximates the filtering abilities of the kidneys. In addition to a creatinine level, it incorporates a person's age and sex.⁷

In healthy adults, a normal eGFR is usually more than 90. An eGFR between 60 and 89 may indicate early-stage kidney disease, whereas an eGFR below 15 indicates kidney failure.⁸

 Stages of Kidney Disease and Treatment

Average Urine Creatinine

A urine creatinine test measures the level of creatinine in the urine. Similar to blood creatinine levels, factors such as age and muscle mass can affect the results of urine creatinine tests.

Often collected over 24 hours, urine creatinine levels typically range from 500 to 2,000 milligrams per day (mg/day).⁹

Low Urine Creatinine

A low level of creatinine in the urine may indicate kidney injury or disease.

To evaluate kidney function, urine creatinine may also be measured as part of a urine albumin-creatinine ratio. The urine albumin-creatinine ratio compares the albumin level with the creatinine level in a urine sample.

Albumin is a protein that serves multiple bodily functions, including maintaining fluid within blood vessels and transporting various substances.¹⁰

Albumin in the urine is a possible sign of kidney damage, as the filtering units of healthy kidneys do not allow it to leak out from the bloodstream.

A normal uACR is below 30 milligrams/gram (mg/g).¹¹ A uACR level of 30 mg/g or higher suggests an increased risk for kidney disease.

 How Albumin in the Urine Is a Possible Sign of Kidney Disease

Deciphering the Meaning of High Creatinine Levels

High creatinine levels are often due to a kidney-related problem, although in some cases, non-kidney-related causes, like diet or exercise, are the culprits.

Kidney-Related Causes

Most people have two kidneys. They are on either side of the spine, just above the waist and below the rib cage.

The kidneys perform numerous essential functions in the body, such as:⁶

• Removing waste products and extra salt and water from the body

• Maintaining electrolytes (e.g., potassium and magnesium) and minerals (e.g., calcium and phosphorous) balances

• Controlling blood pressure

• Releasing a hormone (erythropoietin) involved in red blood cell production

• Maintaining bone health

Elevated creatinine levels often indicate kidney disease, meaning the kidneys are damaged and cannot perform their necessary functions.

Acute kidney injury (AKI), also known as acute kidney failure, occurs when there is an abrupt and often temporary reduction or loss of kidney function.¹²

The numerous causes of acute kidney failure can be organized into three categories:

• Prerenal: Decreased blood flow to the kidney associated with fluid volume depletion (e.g., from vomiting or diarrhea) or low blood pressure (e.g., from heart failure or sepsis)

• Intrinsic: Damage to the kidneys from bacterial or viral infections, certain medicines (e.g., antibiotics or nonsteroidal anti-inflammatory drugs), or vasculitis (inflammation of blood vessels)

• Postrenal: Blockage of the path the urine flows through to leave the body, causing pressure and kidney damage (e.g., enlarged prostate or kidney stone).

 Causes of Acute Renal Failure and Their Treatments

Chronic kidney disease (CKD), also called chronic renal disease, is characterized by a gradual loss of kidney function.  

Left untreated, the kidneys may nearly stop working altogether. At this point—called end-stage renal disease (ESRD)—dialysis or a kidney transplant is required to live.

The most common causes of CKD are diabetes and hypertension (high blood pressure).¹³

While not a complete list, examples of other CKD causes include:

• IgA glomerulonephritis is associated with inflammation of the kidney's filtering units.

• Polycystic kidney disease (PKD) is an inherited condition in which fluid-filled sacs (cysts) form within the kidneys.

• Lupus nephritis is kidney inflammation caused by the autoimmune disease lupus.

Non-Kidney-Related Causes

A high creatinine is not always a sign of a kidney problem because, as mentioned above, several factors can impact creatinine levels.

Scenarios linked to a non-kidney-related "high creatinine" level (both in the blood and urine) include:

• Eating large amounts of cooked meats, as creatine (a substance found in muscle cells) in meat is converted to creatinine from the heat of cooking¹⁴

• Excessive intake of creatine supplements¹⁵

• Recent high-intensity exercise, which increases muscle breakdown¹⁶

Moreover, certain medications, such as Tagamet (cimetidine) or Primsol (trimethoprim), can increase blood (not urine) creatinine levels by retaining creatinine in the bloodstream.¹⁷ The good news is that while these medicines may increase blood creatinine, they do not cause harm to the kidneys.

How Do You Know If Your Creatinine Levels Are High?

Since high creatinine levels do not generally cause symptoms, most people find out they have a high creatinine level after obtaining a routine blood test called a basic metabolic panel (BMP).

The BMP measures blood glucose (sugar), calcium, sodium, potassium, carbon dioxide, chloride, blood urea nitrogen (BUN) and creatinine.

Symptoms Associated With High Blood Creatinine Levels

Many people with high blood creatinine levels have no symptoms.¹²

If the elevated creatinine levels are due to kidney disease, symptoms often develop when kidney function deteriorates enough to allow fluid and waste products to build up within the body.  

For acute kidney failure, this may be hours to days, depending on the underlying cause.

Common symptoms of kidney disease include:¹⁸

• Urinating less or not at all

• Swelling (edema) of the feet and ankles

• Blood in the urine (hematuria)

• Protein in the urine causing it to appear foamy (proteinuria)

• Trouble breathing (dyspnea)

• Unusual tiredness

• Loss of appetite

• Nausea and vomiting

• Difficulty thinking

• Itchiness (pruritus)

• Seizures (severe cases of acute kidney failure or advanced chronic disease)

With CKD, long-term complications develop as the kidneys become more and more damaged.

Some of these complications include high blood pressure, anemia (low red blood cell count), bone weakness, and an increased risk of heart disease and stroke.¹⁹

 Complications of Chronic Kidney Disease

What Happens Next: Lowering High Creatinine Levels

Lowering high creatinine levels entails first addressing the underlying cause.

This may mean seeing a nephrologist (a doctor specializing in kidney health) if kidney disease is suspected.

The treatment of kidney disease has several goals. Key ones include:¹⁹

• Treating reversible causes of kidney failure (e.g., fluids for vomiting or relieving an obstruction in the urinary tract system).

• Slowing the progression of chronic kidney disease (e.g., controlling high blood pressure and diabetes, if applicable).

• Managing complications of chronic kidney disease (e.g., lowering salt in diet and taking a diuretic for excess fluid).

• Avoiding or adjusting the dose of medications that can harm the kidneys even more (e.g., nonsteroidal anti-inflammatory drugs).

Likewise, if elevated creatinine levels are from lifestyle factors, such as eating a high-protein diet, modifying your behaviors (under the guidance of a healthcare provider) might be reasonable.

Lastly, staying hydrated, avoiding smoking, and maintaining an average body weight are healthy strategies for optimizing kidney health and creatinine levels.

Summary

Creatinine is produced during regular muscle use. It is a marker of kidney function because the kidneys remove it from the body through urine. A high blood creatinine level often indicates an acute or chronic kidney problem.

Numerous factors, including age, sex, body size, diet, and activity, influence creatinine levels. As such, a high creatinine level is sometimes due to non-kidney-related causes like eating large amounts of cooked meats or vigorous exercise that leads to muscle breakdown.

High creatinine levels can be detected on a routine blood test (a basic metabolic panel) and often do not cause symptoms unless a person has acute kidney failure or is in the later stages of chronic kidney disease. 

Lowering elevated blood creatinine levels involves treating the underlying cause—for example, managing kidney disease. It's essential to discuss next steps with a healthcare provider if you have a high creatinine level.