Creatinine – Your Kidney’s Report Card


What Is Creatinine?

Creatinine is a waste product created by your muscles during the breakdown of a compound called creatine, which helps supply energy to muscle tissue. Because the amount of creatinine in the blood tends to remain stable and is filtered out by the kidneys, it serves as a key indicator of how well your kidneys are functioning.

When kidney filtration slows down, creatinine begins to accumulate in the blood. For this reason, measuring creatinine levels is one of the most common ways to evaluate kidney health.

What Do Normal Creatinine Levels Look Like?

Creatinine levels vary slightly depending on age, sex, muscle mass, and hydration status. Generally, men have higher creatinine levels due to greater muscle mass. For most healthy adults, the typical range is approximately:

  • 0.74 to 1.35 mg/dL for men
  • 0.59 to 1.04 mg/dL for women

Levels outside these ranges can indicate changes in kidney function or other underlying issues.

What Causes High Creatinine Levels?

High creatinine levels may suggest that the kidneys are not filtering waste properly.

Common causes of elevated creatinine include:

  • Kidney disease or kidney damage, which slows filtration
  • Dehydration, which concentrates the blood
  • Excessive muscle breakdown, such as after trauma or heavy exercise
  • High-protein diet or use of creatine supplements
  • Certain medications, including NSAIDs, ACE inhibitors, chemotherapy agents, and imaging contrast dyes
  • Blockages in the urinary tract, such as kidney stones or an enlarged prostate

A temporary rise in creatinine can also occur due to vigorous exercise or acute illness.

What Causes Low Creatinine Levels?

Low creatinine levels are less common and may be related to:

  • Muscle wasting, which reduces creatinine production
  • Malnutrition, especially protein deficiency
  • Severe liver disease, which may reduce creatine synthesis
  • Overhydration, which can dilute creatinine concentration
  • Pregnancy, due to increased blood volume and filtration

In some cases, low creatinine may simply reflect low muscle mass, especially in elderly individuals or those with chronic illness.

How Is Creatinine Tested?

Creatinine is typically measured using a simple blood test. However, to get a clearer picture of kidney health, providers often use additional tests, including:

  • Estimated Glomerular Filtration Rate (eGFR), which uses your creatinine level along with age, sex, and race to estimate kidney function
  • Creatinine clearance test, which compares blood and 24-hour urine creatinine levels to measure how well the kidneys are clearing waste
  • Blood urea nitrogen (BUN) and urinalysis, which help assess other markers of kidney and metabolic health

Together, these tests help determine whether the kidneys are filtering waste efficiently and whether further evaluation is needed.

How to Support Healthy Kidney Function

Protecting your kidneys can help maintain stable creatinine levels and reduce the risk of chronic kidney disease. Here are key steps you can take:

  • Stay well-hydrated, especially in hot weather or when exercising
  • Control blood pressure and blood sugar, as hypertension and diabetes are major causes of kidney damage
  • Avoid excessive use of NSAIDs like ibuprofen and naproxen
  • Limit alcohol and processed foods, which can stress the kidneys
  • Eat a balanced diet, rich in plant-based foods, moderate in protein, and low in salt and additives
  • Monitor medications, especially if you take prescriptions known to affect the kidneys
  • Get routine lab work, especially if you have diabetes, hypertension, or a family history of kidney disease

When to Be Concerned

You should talk to your healthcare provider if you notice:

  • Swelling in your legs, ankles, or face
  • Fatigue or difficulty concentrating
  • Persistent nausea or a metallic taste in your mouth
  • Changes in urination—either too much, too little, or foamy urine
  • Lower back pain near the kidneys
  • Unexplained high blood pressure

These symptoms may indicate worsening kidney function and require immediate evaluation.

Final Thoughts

Creatinine is more than just a number on a lab report—it’s a vital sign of how well your kidneys are working. By understanding what affects your creatinine levels and taking proactive steps to support kidney health, you can reduce your risk of chronic kidney disease and improve your overall wellness.

If you’ve had elevated or low creatinine levels on recent labs, speak with your healthcare provider about additional testing, dietary changes, and medications that may be contributing to the result.

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