I am Dr. Mori, Director of Akabane Mori Clinic—a specialized facility dedicated to dialysis prevention in Tokyo.

Today, I will be explaining 'creatinine,' a key indicator of your kidney function.

I have written this guide specifically for those who were told their creatinine levels were high during a health checkup and are concerned about their kidney health.

If you are living in Japan and have just received a health checkup result showing high creatinine, this guide is for you.

Many of my international patients come to me feeling "lost in translation"—not just because of the language, but because of the way kidney health is managed in Japan.

Finding a high creatinine level on your blood test doesn't always mean you are heading toward dialysis, but it is a "red flag" that should never be ignored.

In this guide, I will explain exactly what creatinine is, why your levels might be elevated due to your life in Japan, and how we can work together to protect your kidneys.

Let’s look at the facts and take the right steps to secure your health.

What is Creatinine?

Creatinine is a waste product produced by the breakdown of creatine in your muscles during daily activity.

Under normal conditions, the kidneys filter this waste from the blood and excrete it through urine.

However, if kidney function declines, creatinine levels in the bloodstream begin to rise because the body cannot effectively clear it.

Consequently, measuring the concentration of creatinine in the blood is a vital diagnostic tool used to estimate how well your kidneys are currently functioning.

 

Why is Your Creatinine High? 3 Common Patterns

There are generally three primary reasons why creatinine levels may be elevated:

1. Lifestyle-Related Diseases: Conditions such as hypertension (high blood pressure) and diabetes can damage the kidneys over time.
2. Medical Conditions: This includes immune system disorders, genetic diseases, or urological conditions that obstruct or affect kidney function.
3. Non-Renal Factors: High muscle mass or intense exercise can raise levels even when kidney function is perfectly normal.

To determine the exact cause, doctors perform specialized blood work, urinalysis, and ultrasound imaging.

Identifying the root cause is critical because treatment is tailored specifically to that factor; conversely, if the elevation is due to muscle mass alone, medical intervention is unnecessary and should be avoided. Always prioritize a thorough diagnostic evaluation before beginning any treatment.

 

Symptoms of High Creatinine

In the early stages, slightly elevated creatinine levels typically produce no symptoms at all.

Most people do not feel physical changes until kidney function has significantly declined.

Depending on a patient's age and overall health, noticeable symptoms generally only appear once creatinine reaches levels of 2.0–3.0 mg/dL or higher.

At this stage, kidney function has often deteriorated to the point where dialysis may be required within a few years.

Common symptoms associated with these advanced levels include:

• Edema (Swelling): Particularly in the legs, ankles, or around the eyes.
• Anemia: Leading to pale skin and shortness of breath.
• Fatigue: A persistent feeling of tiredness or general malaise.

Because the early stages are "silent," regular blood tests are essential for early detection before these symptoms manifest.

 

Risks of Ignoring High Creatinine Levels

The kidneys are resilient organs that often show no symptoms until damage becomes severe.

Because of this "silent" nature, abnormalities are typically only detected through routine blood work and urinalysis.

Unfortunately, since there is no physical pain or discomfort in the early stages, many people ignore elevated creatinine levels.

By the time symptoms actually appear, the damage is often advanced—a situation frequently described as "too little, too late."

As a general rule, kidney function that has significantly declined rarely recovers.

Therefore, early detection is the only way to intervene before permanent damage occurs.

 

Comprehensive Tests for Abnormal Creatinine Levels

Since creatinine alone is insufficient to fully assess kidney health, a comprehensive evaluation using blood and urine tests is necessary.

We primarily use eGFR, Cystatin C, Urine Protein, and Kidney Ultrasound to make an accurate diagnosis.

 

1. eGFR (Estimated Glomerular Filtration Rate)

Think of eGFR as the "advanced version" of a creatinine test.

It calculates kidney function by combining your creatinine level with your age and gender.

Threshold: An eGFR of 60 mL/min/1.73m² or less suggests potential kidney disease.

Important Note for International Patients:If you have received health checkup results in Japan, the eGFR value is typically calculated using a formula specific to the Japanese population. Because body composition and muscle mass vary by ethnicity, these values may not be accurate for everyone.

• Asian Patients: The standard Japanese formula is generally appropriate.
• Western (Caucasian) or African-Descent Patients: Due to differences in physique and muscle mass, we recommend using a different calculation tool (such as the CKD-EPI formula) to get a more accurate assessment of your kidney health.

Tool: You can calculate your own eGFR using the "Kidney Function Measurement Tool" on the National Kidney Foundation website.

 

2. Cystatin C

Creatinine results can be inaccurate for individuals with high muscle mass, such as athletic young men.

In these cases, we measure Cystatin C.

This blood marker provides a highly accurate reading of kidney function regardless of a person’s muscle volume.

We particularly recommend the Cystatin C test for our international patients. Since physical build and muscle mass can vary significantly across different ethnicities, standard Japanese creatinine-based formulas may not always provide the most precise picture.

Testing Cystatin C allows us to bypass these physical variables and get a clear, "true" reading of your kidney health, regardless of your background or fitness level.

 

3. Urine Protein

While eGFR and Cystatin C are blood markers, Urine Protein is the most critical indicator found in a urinalysis.

Standard health checkups use a scale (Negative, 1+, 2+), but for a formal diagnosis, we must perform a detailed test to measure the exact amount (grams) of protein being excreted.

Creatinine and Cystatin C measure your kidneys' current workload (how they are performing right now), while Urine Protein acts as a future SOS signal, warning of potential damage before it becomes permanent.

4. Kidney Ultrasound (Echo)

To identify the underlying cause of decreased kidney function, we use ultrasound to examine the following physical characteristics:

• Size: Checking if the kidneys have shrunken (suggesting chronic damage) or are abnormally enlarged.
• Surface Texture: Looking for a rough or uneven surface, which can be a sign of scarring or long-term disease.
• Swelling: Ensuring there is no hydronephrosis (swelling caused by a backup of urine) or other obstructions.　etc

This is a safe, painless procedure with no radiation exposure, and we actively perform it at our clinic to ensure a thorough investigation.

 

Treatment and Management of High Creatinine

Once a diagnosis is made, the focus shifts to treatment.

However, it is important to understand that kidney function typically does not recover once it has declined.

Therefore, "lowering" creatinine is rarely the goal; instead, the priority is to prevent levels from rising further.

Effective kidney management relies on three pillars: Diet, Exercise, and Medication.

• Dietary Therapy: The primary focus is managing salt intake and ensuring balanced nutrition suited to your kidney health.
• Exercise Therapy: Engaging in aerobic exercise and strength training is vital. We also recommend Kidney Rehabilitation, a specialized exercise therapy designed specifically for kidney patients.
• Medication: Managing blood pressure and blood sugar is critical. We often use a combination of medications that directly protect the kidneys, such as RAS inhibitors and SGLT-2 inhibitors.

To Those Seeking a Deeper Understanding

If you have been told your creatinine is high, you may feel anxious and have been searching for answers online. As we’ve discussed, high creatinine can be caused by many factors, and sometimes it doesn't even reflect the true state of your kidneys.

The most important advice is this: Do not make drastic dietary changes on your own immediately. In our clinic, we often see patients whose kidney condition actually worsens because they changed their diet without a proper diagnosis. Before you act, you must undergo specialized testing to verify the actual state of your kidneys.

 

Final Thoughts: Don’t Rush, Start with the Right Diagnosis

We understand that being told your "kidney numbers are high" can be a shocking and stressful experience, leading many to search for answers online.

As we have discussed, high creatinine levels can be caused by many factors, and sometimes they don't even reflect a real problem with the kidney itself.

If you have been told your creatinine is high, the most important step is to follow a systematic diagnostic process before jumping into treatment.

The biggest mistake you can make is immediately changing your diet without a professional diagnosis.

In our outpatient clinic, we often see patients whose kidney condition actually worsens because they started a restrictive diet before understanding their true status.

First, undergo specialized testing to verify if there is a genuine issue.

A Note to Our International Community

Currently, our clinic provides consultations for over 10,000 Japanese patients annually.

At this time, we are still developing our full English-language support systems.

However, we have exciting plans for the future:

Specialized Health Checkups: We are considering launching self-pay kidney health screenings specifically designed for international residents in Japan.

Information for Expats: Starting from February 2026, we will be releasing a series of kidney health resources tailored for the international community over the next six months.

Please check back on this site regularly for updates.

We are committed to helping everyone living in Japan protect their kidney health.

Kidney Self-care Academy