What Is Creatinine?

Creatinine is the end product of muscle metabolism, removed from the blood by the kidneys. The normal blood creatinine level is 0.5–0.9 mg/dL for women and 0.7–1.2 mg/dL for men. Elevated creatinine points to impaired kidney function and warrants a consultation with a doctor.

As a rule, changes in creatinine levels are not accompanied by specific sensations — at least not until the value reaches a critical threshold. Creatinine itself is not toxic; it is simply an "indicator."

A high value means that the kidneys can no longer filter other toxins either. Any possible symptoms are caused precisely by the build-up of these other substances.

Creatinine is monitored through a biochemical blood test, and, when necessary, a urine test and eGFR assessment are also used.

This test should be performed at least once a year, especially if you have high blood pressure or diabetes. In that case, waiting for symptoms is not justified.

 

What Is Creatinine?

 

Creatinine is a chemical substance produced in the muscles during the use of energy. It is a kind of "waste" product of the body's metabolism and is excreted in the urine. A certain amount of creatinine is present in everyone's blood, but an excessive level may be a sign of a kidney problem.

Below is a closer look at what this substance actually is.

 

A product of muscle energy metabolism

 

Our muscles contain a substance called creatine, which is needed to produce energy quickly — especially during physical exertion. When creatine breaks down and releases energy, the end product, creatinine, is formed.

It is worth noting that this process is constant and stable. The production of creatinine depends directly on a person's muscle mass. Muscle volume does not change sharply from day to day, so the supply of this substance into the blood is also constant and predictable. This is precisely what makes the indicator a reliable benchmark for assessing kidney function.

 

Filtration and excretion

 

Creatinine is no longer useful to the body, so it needs to be "filtered" out of the blood and removed. This function is performed by the kidneys.

• Creatinine reaches the kidney through the bloodstream;
• Healthy kidneys filter it almost completely;
• Ultimately, it is excreted from the body together with urine.

Creatinine is one of the main laboratory markers for assessing kidney function and is often used to calculate eGFR, since eGFR, albuminuria/ACR (the albumin-to-creatinine ratio in urine), and the urine test together are more meaningful.

Stability: Creatinine is a relatively stable indicator for a given individual, although it can be affected by muscle mass, hydration, diet, physical activity, and some medications.

A single route of excretion: Creatinine leaves the body almost exclusively through the kidneys. If the kidneys do not work well, it accumulates in the blood.

Proportionality: Even a small rise in blood creatinine often signals that the kidneys' filtration capacity has decreased. This is otherwise known as the glomerular filtration rate — eGFR.

If the creatinine level in the blood is elevated, it means that the kidneys are not fully performing their function.

 

Creatinine Norm — in Blood and Urine

 

The normal creatinine level in human blood depends on several important factors: sex, age, and muscle mass. Notably, men have a slightly higher value than women, simply because they have, on average, more muscle mass. The normal blood creatinine level is 0.5–0.9 mg/dL (44–80 µmol/L) for women and 0.7–1.2 mg/dL (62–106 µmol/L) for men. In children, the norm is even lower.

[Image: blood creatinine vs urine creatinine comparison]

There are two different tests: blood creatinine and urine creatinine. The amount of creatinine in urine collected over 24 hours shows how much the body excretes.

eGFR is calculated based on the blood creatinine level and other data.

The most important nuance is that blood creatinine rises noticeably only when kidney function is already reduced by about half. This is exactly why a normal creatinine level does not yet mean everything is fine. For this reason, a doctor always considers both indicators — creatinine and eGFR — together.

Urea and creatinine — patients are often curious about the difference between these two indicators.

On a test form, creatinine is often accompanied by urea (BUN). Both are kidney function markers, but they have different origins. Urea is formed in the liver during the processing of protein and is much more strongly affected by diet — eating a lot of meat, or, conversely, very little protein. In this respect, creatinine is more stable and a more specific indicator of kidney function.

Urea and creatinine — doctors are often guided by the ratio of these two indicators.

 

What Does High Creatinine Mean?

 

Elevated blood creatinine often indicates that the body's "filtration system" is working with disruptions. Keep in mind, though, that a high value does not always mean kidney disease.

Now let's look at the main causes.

• Impaired kidney function is the most common cause. When the kidneys' filtration capacity declines, creatinine accumulates in the blood;
• Dehydration: when fluid is lacking, the blood becomes concentrated, which artificially raises the value;
• Intense physical exertion: heavy exercise accelerates the burning of muscle energy, which in turn leads to more creatinine being released;
• Muscle tissue damage: a rise in creatinine indicates that a large amount of metabolic products has entered the bloodstream at once;
• Medications: some antibiotics or non-steroidal anti-inflammatory drugs affect the excretion of creatinine by the kidneys;
• Chronic diseases: diabetes and hypertension are the main risk factors for kidney damage, which, over time, is reflected in rising creatinine levels.

Clearly, high creatinine does not point only to kidney problems and may have other causes.

 

When Should You See a Doctor?

 

A consultation with a nephrologist is essential if high creatinine is accompanied by swelling, changes in urination patterns, fatigue, or fluctuating blood pressure.

 

What does low creatinine mean?

It is worth noting that in clinical practice, a low value is rarer than a high one. As a rule, it points to physiological changes taking place in the body. These include:

• Reduced muscle mass — low creatinine is often recorded in elderly people or in cases of muscle atrophy;
• Pregnancy — during pregnancy, renal blood flow and filtration rate increase, which causes a physiological decline in creatinine levels;
• Liver diseases -  since creatine is synthesized in the liver, severe damage to it (for example, cirrhosis) may become a cause of low creatinine;
• Insufficient nutrition — a sharp protein deficiency in the diet reduces metabolism.

 

How to Lower Creatinine Levels?

 

First of all, it is important to remember that creatinine is not a disease. It is only an indicator. Accordingly, lowering its level requires managing the underlying cause.

Consider the following key factors:

• Regulating water balance — adequate hydration is important, although the amount of fluid depends on the individual's condition;
• Adjusting the diet — in some kidney diseases, a doctor may recommend an individual adjustment of protein intake;
• Optimizing physical activity — when creatinine is high, it is recommended to temporarily reduce intense, strenuous exercise;
• Controlling the underlying disease — stabilizing blood sugar and arterial blood pressure is the main way to prevent further kidney damage;
• Medication therapy — any drug should be taken only as prescribed by a doctor. This is important so that kidney function does not worsen.

Remember that self-treatment and attempts to "lower" the value on your own are unacceptable. For an accurate diagnosis and treatment plan, be sure to consult a specialist.

 

Creatinine Test at Todua Clinic — How to Prepare?

 

If your doctor has prescribed a creatinine test, you should prepare for the procedure.

• Depending on the recommendation of the laboratory or your doctor, the test may be performed on an empty stomach, especially if other biochemical markers are also planned;
• Drinking water is allowed, but coffee, tea and other beverages are not;
• It is recommended not to eat large amounts of meat one to two days before the test, since protein-rich food raises creatinine levels;
• It is also advisable to reduce intense physical activity one day before the test.

Doctors often simultaneously check urea (BUN), electrolytes — potassium, sodium, chloride — and, when necessary, GFR values. This combination helps them see the full picture.

Todua Clinic's central laboratory performs biochemical, hematological and immunological tests, including urine creatinine and the albumin-to-creatinine ratio. Patients are served seamlessly at all three branches of the clinic.

Take a creatinine test at Todua Clinic. Call us at 032 2 57 57 57.

 

Frequently Asked Questions

 

Why does blood creatinine rise?

The most common cause of elevated blood creatinine is impaired kidney function — the kidneys can no longer filter creatinine effectively. Other causes include dehydration, intense exercise, muscle damage, certain medications, as well as diabetes and hypertension. If creatinine is elevated, a consultation with a nephrologist is recommended.

 

What is the normal creatinine level in blood?

The creatinine norm in women is 0.5–0.9 mg/dL (44–80 µmol/L), and in men, 0.7–1.2 mg/dL (62–106 µmol/L). In children, the norm varies by age. If the value deviates from the norm, see a doctor.

 

How can creatinine be lowered?

To reduce creatinine levels, it is important to adjust fluid intake and protein consumption — which may be either increased or decreased, according to a nephrologist's recommendation — as well as to reduce intense physical activity. However, the most important thing is to identify and treat the underlying cause. Self-treatment is not recommended.