Have you ever picked up a blood test report, looked at the letters and numbers on it, and wondered, "What does this mean?"? Most of the time, we listen to what the doctor says, but some of the words on this report are unfamiliar to us. One such word that many people are familiar with, but don't really know, is "Creatine." This little word contains a big story about the health of our body's most important organ, the kidneys. So today, let's talk about it.
Simply put, what is creatinine?
Imagine, when our muscles work properly, that is, when we walk, run, or lift weights, a waste product is produced in that process. That naturally occurring waste product is what we call creatinine. This is not something our body needs. So, the body's most advanced filtering system, our two kidneys, filter and separate these waste products from the blood and excrete them in the urine.
So when a doctor measures the level of creatinine in your blood, he is looking at how well your kidneys are doing their job of filtering. We usually call this test the serum creatinine test.
What are normal creatinine levels?
Because creatinine is produced by muscles, this value can vary depending on a person's muscle mass and body size. In general, men have slightly higher creatinine levels than women because they have more muscle mass.
| Person | Normal Creatinine Range (mg/dL) |
|---|---|
| For women | 0.6 - 1.1 mg/dL |
| For men | 0.7 - 1.3 mg/dL |
The important thing is that these numbers can vary slightly from lab to lab, so only your doctor can give you an accurate assessment of the values in your report.
Relationship between creatinine and kidney function (GFR)
The entire blood volume in our body passes through the kidneys hundreds of times a day. The measurement of this speed at which the kidneys clean the blood is called the Glomerular Filtration Rate , or GFR . Simply put, this is a measure of the efficiency of the kidneys.
Your doctor can't measure your GFR directly. That's where the creatinine test comes in. Your GFR is calculated by substituting factors like your blood creatinine level, age, and gender into a special formula. We call this eGFR (estimated GFR) .
Simply put: An increase in blood creatinine levels may indicate a decrease in the kidneys' filtration capacity (GFR). A GFR value of less than 60 may be a sign of kidney disease.
Why is this creatinine test done?
Doctors mainly order this test to check how well your kidneys are working. Sometimes, they order this test if you have symptoms related to kidney disease.
- Nausea and vomiting
- Appetite
- Frequent fatigue and weakness
- Insomnia problems
- Change in frequency or amount of urination
- Swelling of the legs and ankles
Even if you don't have these symptoms, your doctor will often recommend this test to monitor your kidneys if you have conditions like diabetes, hypertension, heart disease, or liver disease . It is also done to see if certain medications are affecting your kidneys.
How to do the test?
There are two main ways to check creatinine levels:
1. Blood test (eGFR Blood Test): This is the most commonly used method. A blood sample is taken from your arm as usual, the creatinine level in it is measured, and the eGFR value is calculated. You may be asked to fast for a few hours for this.
2. Creatinine Clearance Test: This method is not used much anymore. In this, all the urine excreted over a 24-hour period needs to be collected in a special container. The amount of creatinine in that urine sample is measured to get an idea of the functioning of the kidneys.
What do the results say?
A low GFR indicates impaired kidney function. This condition can be sudden (acute) or long-term (chronic).
Doctors classify the severity of chronic kidney disease into several stages based on the GFR value.
| Stage | GFR value | Meaning |
|---|---|---|
| I | 90 or above | Normal kidney function |
| II | 60-89 | Mildly decreased activity |
| IIIa | 45-59 | Mild chronic kidney disease |
| IIIb | 30-44 | Moderate chronic kidney disease |
| IV | 15-29 | Acute chronic kidney disease |
| V | Under 15 | Kidney failure (often requiring dialysis) |
Other reasons for abnormal creatinine levels
The important thing is that an elevated creatinine level does not always mean kidney disease. Sometimes this value can change for other reasons.
- Intense exercise: When you exercise excessively, your muscles produce more creatinine.
- A diet high in red meat: Since red meat contains creatinine, eating too much of it can temporarily increase blood levels.
- Certain medications: Some antibiotics and other medications can cause changes in creatinine levels.
- Excessive muscle mass: A bodybuilding person may have higher creatinine levels than the average person.
- Dehydration: Even if there is not enough water in the body, creatinine levels can become concentrated and show a high value.
- Heart failure and bladder problems.
What to do if GFR is low?
If your doctor determines that your GFR is low, he or she will determine the cause and recommend a treatment that is right for you.
The two main causes of chronic kidney disease are high blood pressure and diabetes. If you have these conditions, the first step is to control them well with a good diet, exercise, and prescribed medications.
If the cause is not clear, or if the condition is severe, your doctor will refer you to a nephrologist .
Regularly checking your GFR can help you see how your kidney function is changing over time. Your doctor can then adjust your medication prescriptions accordingly.
It is very important not to use any over-the-counter painkillers, herbs, or other supplements without first talking to your doctor. Some of these can harm your kidneys.
Kidney function naturally declines as we age, so it's best to take care of this as soon as possible and preserve any kidney function you have.
Take-Home Message
- Creatinine is a waste product produced when our muscles work. It is filtered and removed by the kidneys.
- Measuring your blood creatinine levels (especially your eGFR) is one of the most important tests to assess the health of your kidneys.
- Although an increase in blood creatinine levels or a decrease in GFR is often a sign of kidney disease, this is not always the case. Other factors can also play a role.
- Good control of diabetes and high blood pressure is essential to protect the kidneys.
- Always discuss your test results and any medications you are taking (including over-the-counter painkillers) with your doctor.
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