High creatinine levels may indicate one of several underlying health conditions requiring medical treatment. Following treatment of the underlying cause, creatinine levels should return to normal.

Creatinine is a waste product of the muscles. In a healthy body, the kidneys filter creatinine from the blood and excrete it through the urine. High levels of creatinine can indicate kidney issues.

In this article, we explore what creatinine is and what can cause high levels. We also look at symptoms of high creatinine, when to worry about creatinine levels, and the treatment options.

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Creatinine is a byproduct of normal muscle function. It is a metabolite of creatine phosphate, which the muscles use as an energy source.

The greater someone’s muscle mass, the higher their creatinine levels. For this reason, males tend to have higher creatinine levels than females.

The primary way in which the body removes creatinine from the blood is by filtration through the kidneys and then excretion in the urine.

The creatinine levels that experts consider to be normal may vary among different hospitals and laboratories.

According to the British Medical Journal, the usual reference range for serum creatinine is 60–110 micromoles per liter (mcmol/l), or 0.7–1.2 milligrams per deciliter (mg/dl), for males and 45–90 mcmol/l (0.5–1.0 mg/dl) for females.

If creatinine is above these levels, doctors may consider it high.

However, their decision will depend on someone’s muscle mass and certain other factors, such as age, sex, and hydration levels.

Doctors take a blood sample to test creatinine levels. They then use a formula to estimate creatinine clearance.

In some cases, they may also request that the individual collects all of their urine over 24 hours and brings it to the laboratory.

The doctor can then compare the urinary creatinine level with that of the blood. These results show how much creatinine the kidneys are filtering out of the body and how well they are functioning.

High creatinine levels usually indicate that the kidneys are not working as they should. Possible causes of this dysfunction include:

Outside of kidney function, several other factors can temporarily raise creatinine levels above normal. These include dehydration and consuming large amounts of protein — either through food sources or nutritional supplements.

High intensity exercise can also increase certain blood biomarkers, including creatinine.

A person undergoing a creatinine test should let the doctor know if they are taking any medications, fasting, or adhering to a protein-rich diet.

Certain medicines can cause a temporary increase in serum creatinine levels or damage the kidneys.

Some health conditions can also damage these organs, leading to increased creatinine levels. These conditions include:

People with high creatinine levels may experience different symptoms, depending on the cause.

Drug toxicity

Antibiotics, cardiovascular drugs, diuretics, and some other medications can cause kidney damage and affect how well the kidneys function.

The symptoms include:

  • fluid retention
  • feeling weak or fatigued
  • confusion
  • nausea
  • shortness of breath
  • irregular heart rate
  • chest pain

Kidney infection (pyelonephritis)

An untreated kidney infection can damage the kidneys, and, in extreme cases, it can even cause kidney failure.

People may experience the following symptoms:

  • fever or chills
  • pain in the back, side, or groin
  • cloudy, dark, bloody, or foul-smelling urine
  • frequent, painful urination
  • nausea and vomiting

Glomerulonephritis

Lupus, Goodpasture’s syndrome, and infections can cause glomerulonephritis, which can lead to kidney damage and failure.

Possible symptoms include:

  • high blood pressure
  • blood or protein in the urine
  • bubbly or foamy urine due to high levels of protein
  • swelling of the ankles and face

Diabetes

In people with diabetes, blood sugar levels can become too high, leading to health problems, including kidney disease.

The symptoms of type 1 diabetes may develop suddenly, but the symptoms of type 2 diabetes tend to present more gradually.

In both types of diabetes, symptoms may include:

  • increased thirst and appetite
  • frequent urination
  • fatigue
  • blurry vision
  • slow-healing wounds
  • numb or tingling hands and feet

High blood pressure

High blood pressure measurements show that the force of blood against the walls of the arteries is too high.

High blood pressure can damage blood vessels surrounding the kidneys, affecting kidney function and, in turn, causing high creatinine.

Many people with high blood pressure experience no symptoms, and doctors may only detect the issue during a regular health screening.

Heart disease

Atherosclerosis, congestive heart failure, and other conditions that affect the heart can also affect kidney function.

The symptoms of heart disease depend on the specific type of this condition, but they may include:

  • chest pain (angina)
  • shortness of breath
  • nausea
  • fatigue and weakness
  • irregular heartbeat
  • swelling in the legs or feet

Urinary tract blockage

If the urinary tract becomes blocked by kidney stones, tumors, or an enlarged prostate, urine can accumulate in the kidneys, leading to hydronephrosis.

Symptoms can include:

  • pain in the back or side
  • nausea and vomiting
  • painful urination
  • blood in the urine
  • fever

Kidney failure

Kidney failure means that the kidneys have stopped working. It can be either acute, with symptoms that come on quickly, or chronic, with symptoms developing over time.

People should watch for these symptoms which could indicate acute kidney failure:

  • swelling in the feet and ankles
  • too much or too little urine
  • breathing difficulties
  • nausea and vomiting
  • irregular heartbeat
  • confusion
  • weakness

The following symptoms may be present if kidney failure is chronic:

  • difficulty sleeping
  • itching
  • lack of appetite
  • muscle cramps

Anyone experiencing any new and unexplained symptoms should consult a medical professional. It is particularly important to seek advice if the symptoms indicate kidney disease, diabetes, or heart problems.

Seeking prompt medical advice and treatment can prevent a health issue from becoming more severe.

The treatment for high creatinine levels depends on the underlying cause.

When a kidney infection is responsible for high creatinine levels, treatment with an antibiotic should return them to normal.

Likewise, if the increased creatinine levels are due to high blood pressure, taking medication to treat this should also lower creatinine levels.

Depending on the cause, doctors may also recommend making changes to everyday habits, such as reducing protein intake and increasing dietary fiber. Such adjustments may help someone manage their creatinine levels.

The outlook for people with high creatinine levels varies depending on the cause.

For those experiencing a temporary increase in creatinine levels, any symptoms should usually resolve quickly following suitable treatment of the underlying condition.

Individuals who can successfully control their diabetes or high blood pressure should also notice a positive effect on their kidney health and creatinine levels.

If someone has kidney failure, they may need medications and dialysis treatments to filter toxins and waste products from the blood. A doctor may also recommend a kidney transplant.

If the kidneys are not functioning as they should, creatinine levels can increase in the blood.

Several factors can cause high creatinine levels. These factors range from diet and medications to underlying health conditions.

Levels should return to normal following treatment of the underlying issue.

Anyone experiencing any symptoms associated with high creatinine should seek medical advice.

Prompt treatment can reduce any potential kidney damage and increase the likelihood of a complete recovery.