Creatinine is a waste product that’s made by your muscles. Your kidneys work to filter creatinine as well as other waste products out of your blood. After being filtered, these waste products are then expelled from your body in urine.

Measuring creatinine levels can provide important insights into how your kidneys may be functioning. Your doctor can measure creatinine levels in both your blood and in your urine.

Creatinine levels that are above or below normal ranges may indicate the presence of a health condition. Let’s take a closer look at high creatinine, the symptoms that go along with it, and when to see a doctor.

Creatinine levels can be determined using a blood test or a urine test.

Blood creatinine test

You may also see this test referred to as a serum creatinine test. During this test, blood is collected from a vein in your arm and is then sent to a lab for further analysis.

According to Mayo Clinic, the normal range of creatinine (for an adult) in the blood is typically:

  • U.S. units: 0.84 to 1.21 milligrams per deciliter (mg/dL)
  • European units: 74.3 to 107 micromoles per liter (umol/L)

Creatinine levels above the normal range values may be considered high. Your doctor may want to confirm these values by using a urine test or by repeating the blood test.

Urine creatinine test

Your doctor may collect a random (single) urine sample for this test, but they’ll more likely request a 24-hour sample. A 24-hour urine sample involves collecting your urine over a period of 24 hours.

According to Mayo Clinic Laboratories, the normal urine creatinine ranges in a 24-hour urine sample are:

  • U.S. units: 955 to 2,936 milligrams per 24 hours (mg/day) for men; 601 to 1,689 mg/24 hours for women
  • European units: 8.4 to 25.9 millimoles per 24 hours (mmol/day) for men; 5.3 to 14.9 mmol/day for women

Urine creatinine levels above these ranges are considered high, and additional testing or repeat testing may be required.

The amount of creatinine in the urine can also be used in conjunction with serum creatinine results to calculate your creatinine clearance, which measures how well your kidneys are filtering your blood.

A Note on reference ranges and Results

Creatinine levels may vary due to factors like by age, sex, race, hydration, or body mass. Additionally, standard reference ranges can vary from lab to lab.

It’s important that you don’t try to interpret your results on your own. Your doctor will work with you to evaluate and interpret your results and what they may mean.

So what does it mean if you have high creatinine levels?

Generally speaking, high levels of creatinine can indicate that your kidneys aren’t working well.

There are many possible causes of high creatinine, some of which may be a one-time occurrence. Examples can include things such as dehydration or intake of large amounts of protein or the supplement creatine. All of these can be temporarily hard on your kidneys.

However, other causes of high creatinine may point to a health condition. Many of these conditions can cause damage or disease that impacts kidney function. They can include:

The symptoms of high creatinine can depend on the condition that’s causing it.

Drug toxicity (drug-induced nephrotoxicity)

Some medications can cause damage to the kidneys and impair their ability to function. Examples of such drugs are:

Symptoms that go along with high creatinine and can develop rapidly may include:

  • fluid retention, particularly in your lower body
  • passing low amounts of urine
  • feeling weak or fatigued
  • confusion
  • nausea
  • shortness of breath
  • irregular heart rate
  • chest pain

Kidney infection (pyelonephritis)

A kidney infection is a type of urinary tract infection (UTI). It can happen when bacteria or viruses infect other parts of your urinary tract before moving up into the kidneys.

If left untreated, kidney infections can cause damage to your kidneys and even kidney failure. Some kidney infection symptoms to look out for include:

  • fever
  • pain localized to your back, side, or groin
  • urination that’s frequent or painful
  • urine that appears dark, cloudy, or bloody
  • bad-smelling urine
  • chills
  • nausea or vomiting

Glomerulonephritis

Glomerulonephritis occurs when the parts of your kidneys that filter your blood become inflamed. Some potential causes include infections or autoimmune diseases like lupus and Goodpasture syndrome.

Glomerulonephritis can lead to kidney scarring and damage as well as kidney failure. Symptoms of the condition include:

  • high blood pressure
  • blood in the urine, which may make it appear pink or brown
  • urine that appears foamy due to high levels of protein
  • fluid retention in the face, hands, and feet

Diabetes

Diabetes is a condition in which your blood sugar is too high. Elevated blood sugar levels can lead to a variety of health problems, one of which is kidney disease.

There are two types of diabetes — type 1 and type 2. Symptoms of type 1 diabetes can develop quickly while symptoms of type 2 often develop gradually. General symptoms of diabetes include:

  • feeling very thirsty
  • frequent urination
  • increased appetite
  • feeling fatigued
  • blurry vision
  • sensations of numbness or tingling in the hands and feet
  • slow wound healing

High blood pressure

High blood pressure happens when the force of the blood pushing on the walls of your arteries is too high. This can damage or weaken the blood vessels around the kidneys, impacting kidney function and causing high creatinine.

Since high blood pressure often has no symptoms, many people don’t know they have it. It’s often detected during a routine health screening.

Heart disease

Conditions affecting the heart and blood vessels, such as atherosclerosis and congestive heart failure, can also impact kidney function. These conditions can affect blood flow through the kidneys, leading to damage or loss of function.

Symptoms of atherosclerosis don’t usually occur until an artery is severely narrowed or completely blocked. They can also depend on the type of artery affected. Some general symptoms include:

  • chest pain (angina)
  • shortness of breath
  • abnormal heart beat (arrhythmia)
  • feeling tired or weak
  • stroke-like symptoms, such as paralysis or trouble speaking

Symptoms of congestive heart failure can include:

  • difficulty breathing or shortness of breath
  • feeling tired or fatigued
  • swelling in the abdomen, legs, or feet

Urinary tract blockage

Your urinary tract can become blocked due to a variety of things, such as kidney stones, an enlarged prostate, or tumors. When this happens, urine may accumulate in the kidneys, leading to a condition called hydronephrosis.

Symptoms of a urinary tract blockage can develop quickly or slowly over time depending on the cause. Some signs to look out for in addition to a high creatinine level include:

  • pain in your back or side
  • frequent or painful urination
  • blood in your urine
  • passing small amounts of urine or having a weak urine stream
  • feeling tired or fatigued

Kidney failure

Kidney failure refers to a decrease in kidney function and one of the most common causes of high creatinine. It can be either acute or chronic. The symptoms of acute kidney failure can come on quickly while those of chronic kidney failure develop over time.

Some symptoms of kidney failure to watch for include:

  • fluid retention, particularly in your lower body
  • passing low amounts of urine
  • feeling weak or fatigued
  • headache
  • confusion
  • nausea
  • trouble sleeping
  • muscle cramping
  • feeling itchy
  • shortness of breath
  • chest pain

You should always call your doctor if you’re experiencing new, unexplained, or recurring symptoms, particularly if they’re consistent with conditions such as kidney disease, diabetes, or heart disease.

Your doctor will work with you to evaluate your symptoms and determine the treatment that’s right for you.

It’s important to remember that chest pain and acute kidney failure should always be taken seriously. You should be sure to seek immediate medical attention if you’re experiencing either one.

There are many potential causes of high creatinine levels. Additionally, the symptoms of high creatinine can vary depending on the cause.

In many cases, medications can help resolve high creatinine levels by treating the condition that’s causing the increase. Some examples include antibiotics for a kidney infection or medications that help control high blood pressure.

In cases of kidney failure, dialysis may be required in addition to medications to help filter toxins and waste products from your blood. In severe cases or end-stage cases, a kidney transplant may be required.