Creatinine: blood test, normal levels and ways to reduce high levels

How does the body produce creatinine?

The content of the article

Creatine is formed from creatine. Creatine is a nitrogen-containing carboxylic acid synthesized in muscles, kidneys, and pancreas. Sometimes it is additionally taken by athletes as an auxiliary nutritional supplement.

During fatigue, muscles convert creatine into energy, which powers muscle contractions. As a result, creatinine is obtained as the final product of metabolism. Creatinine is then released into the blood and excreted from the body through the urine of the kidney.

Although creatinine does not actively benefit or harm the body, the amount of creatinine in the blood can be measured to assess kidney health. For this reason, doctors often use a creatinine test to screen for chronic kidney disease (CKD) or kidney failure.

Purpose and circulation of creatinine

All chemical compounds circulating in the body can be divided into those that are constantly included in the metabolism in the form of various metabolites that transform into each other, and those substances that belong to the group of waste waste. The latter are subject to mandatory removal from the body. Blood creatinine is considered one of the few representatives of waste substances that exhibit toxic properties to tissues. Since its formation occurs constantly, it must be excreted just as regularly.

The central organs and tissues that regulate its metabolism are the kidneys, liver and muscles. Creatinine metabolism is designed in such a way that primary formation occurs in muscle tissue. It contains creatine phosphate, which breaks down during muscle contractions to produce a powerful flow of energy needed to perform movements and loads. Creatine phosphate is formed in the liver by combining the amino acid creatine with a phosphoric acid residue (phosphorylation process), from where it is sent through the bloodstream to the muscles. After the breakdown of creatine phosphate, creatinine is formed, which is excreted by the kidneys in urine.

Important to remember! The reasons for the increase in creatinine may be due to a violation of any of the stages of its circulation and metabolism!

Why is a creatinine test prescribed?

Creatinine testing is used to evaluate the kidneys' ability to filter blood. Most often it is prescribed for:

• suspected development of renal failure;
• any kidney diseases - pyelonephritis, polycystic disease, urolithiasis, glomerulonephritis;
• severe injuries or burns;
• any injuries, atrophy or muscle tears;
• diseases of the endocrine system;
• diseases of the cardiovascular system;
• acute inflammatory diseases;
• sepsis;
• postoperative period.

Indicator norm

It is logical that the creatinine norm cannot be the same for all people. Its fluctuations depend on gender, age and some other factors given below. Generally accepted standards from which to base when assessing this component of a biochemical blood test are given in the table. Units of measurement are mmol/l.

What is a good creatinine level?

In most cases, the normal range of creatinine found in the blood for people with healthy kidneys is:

Creatinine is a product of the non-enzymatic breakdown of creatine and creatine phosphate, which is formed in muscles. It is excreted from the body by the kidneys.

Synonyms Russian

1-methylglycocyamidine, a product of the conversion of creatine phosphate, creatinine in the blood.

English synonyms

Creatinine, Creat, Serum Creat, Cre, Blood creatinine, Serum creatinine, Urine creatinine.

Research method

Kinetic method (Jaffe method).

Units

μmol/L (micromoles per liter).

What biomaterial can be used for research?

Venous, capillary blood.

How to properly prepare for research?

• Do not eat for 12 hours before the test.
• Avoid physical and emotional stress 30 minutes before the test.
• Do not smoke for 30 minutes before the test.

General information about the study

Creatinine is a residual product produced in muscles when a substance called creatine is broken down. Creatine is part of a cycle that provides the body with energy to contract muscles. After 7 seconds of intense physical activity, creatine phosphate is converted to creatine, which then turns into creatinine, which is filtered in the kidneys and excreted in the urine. Creatine and creatinine are stably produced by our body in constant quantities. Almost all creatinine is excreted by the kidneys, so its concentration in the blood is a good indicator of kidney function. The amount of creatinine produced depends on total body weight and, in particular, muscle mass. Therefore, for example, creatinine levels in men will be significantly higher than in women and children.

A small part of it (15%) is secreted by the tubules, but it is mainly produced due to filtration in the glomeruli. The level of creatinine in the blood does not go beyond the normal range until glomerular filtration rate decreases to critical values, especially in patients with low muscle mass. The creatinine level then rises.

It is precisely because of the large number of components (muscle mass, gender, age) that affect the concentration of creatinine in the blood that this study is not the best screening test for detecting renal failure. At the same time, creatinine is a more sensitive indicator of kidney disease than urea.

What is the research used for?

• To assess renal function.
• To assess the function of major organs and systems (in combination with other studies).
• To evaluate kidney dysfunction and the effectiveness of its treatment if creatinine or urea are outside the normal range and the patient has an underlying chronic disease, such as diabetes, that affects the kidneys.
• If the level of creatinine in the blood and urine is known, the creatinine clearance (Rehberg test) can be calculated - this test shows how effectively the kidneys filter small molecules such as creatinine from the blood.
• To calculate the glomerular filtration rate to confirm kidney damage.

When is the study scheduled?

• At certain intervals in case of already known kidney disease or a disease that can cause deterioration of kidney function (together with a test for urea and microalbuminuria).
• When diagnosing skeletal muscle diseases.
• Before and after the hemodialysis procedure.
• For symptoms of kidney dysfunction: weakness, fatigue, decreased attention, poor appetite, sleep problems,
• swelling of the face, wrists, ankles, ascites,
• foamy, red or coffee-colored urine
• decreased diuresis,
• problems with urination: burning, intermittency, change in frequency (predominance of nocturnal diuresis),
• pain in the lumbar region (especially on the sides of the spine), under the ribs,
• high pressure.

What do the results mean?

Reference values ​​(creatinine norm):

Creatinine

GFR (glomerular filtration rate): 60 and above.

Causes of increased creatinine levels

• Acute and chronic renal failure (amyloidosis, kidney damage due to diabetes, etc.).
• Failure of the cardiovascular system (myocardial infarction, cardiogenic shock, myocardial dystrophy, etc.).
• Massive destruction of muscle tissue (crash syndrome) and release of creatinine from cells.
• Burns (massive necrosis of cells with the release of their contents into the intercellular substance).
• Acromegaly.
• Gigantism.
• Hyperthyroidism.
• Dehydration (blood thickening and relative hypercreatininemia).
• Excessive physical activity.
• Excessive consumption of meat products.
• Radiation sickness.
• Obstruction of the urinary tract.
• Taking nephrotoxic drugs (mercury compounds, sulfonamides, thiazides, aminoglycoside antibiotics, cephalosporins and tetracycline, barbiturates, salicylates, androgens, cimetidine, trimethoprim-sulfamethoxazole).
• Damage to the blood vessels of the glomerular apparatus of the kidneys (glomerulonephritis), which may be a consequence of an infectious or autoimmune disease.
• Bacterial kidney infection (pyelonephritis).
• Necrosis of the tubular epithelium (acute tubular necrosis), caused, for example, by drugs or toxins.
• Prostate disease, nephrolithiasis or other factors causing obstruction of the urinary system.
• Reduced blood flow to the kidneys due to shock, dehydration, acute heart failure, atherosclerosis, or complications of diabetes.

Reasons for decreased creatinine levels

• Starvation.
• Overhydration (blood dilution – relative hypocreatininemia).
• Amyotrophy.

What can influence the result?

• Factors distorting the result Pregnancy (especially the first and second trimesters).

Creatinine is higher than normal - reasons

Physiological reasons:

• strength sports – powerlifting, bodybuilding, wrestling;
• large amount of muscle mass;
• predominance of meat dishes in the diet;
• the use of certain medications, for example, tetracycline antibiotics, non-steroidal anti-inflammatory drugs.

Pathological reasons:

• acute and chronic kidney diseases;
• diseases of the cardiovascular system;
• hyperthyroidism – excessive production of the hormone thyroxine by the thyroid gland; radiation sickness;
• oncological diseases;
• muscle injuries;
• septic shock;
• extensive burns;
• endocrine diseases.

Hypercreatinemia as a sign of disease

An increase in creatinine is called hypercreatininemia. It can act as the main diagnostic criterion or an additional sign of many different diseases. Based on the degree of increase compared to the norm, one can roughly determine the causes of this condition. In this regard, it is advisable to highlight.

Slight and moderate hypercreatininemia (exceeding the norm by several tens of units)

• Any kidney pathology complicated by degrees 1 and 2 of organ failure;
• Liver damage of a toxic, inflammatory or cirrhotic nature;
• Massive tissue necrosis with gangrene of the limbs and internal organs;
• Traumatic damage to muscle tissue, bones and extensive skin burns;
• Hyperfunction of the thyroid gland (thyrotoxicosis);
• Diabetic nephropathy due to diabetes mellitus;
• Hyperfunction of the adrenal glands (hyprecorticism);
• Myasthenia;
• Toxic effects on the body caused by exposure to harmful substances or against the background of various serious diseases (infections, purulent-septic conditions, severe injuries, intestinal obstruction, peritonitis, etc.)
• Side effects of medications that have a nephrotoxic effect;
• Autoimmune pathology with massive damage to connective tissue (rheumatoid arthritis, lupus erythematosus, vasculitis);
• Dehydration of the body caused by insufficient fluid intake or excessive fluid loss;
• Decompensated heart failure with severe stagnation in the systemic circulation;
• Toxicosis complicating the course of pregnancy.

Severe hypercreatininemia (exceeding the norm by 100 mmol/l or more)

• Kidney diseases accompanied by stage 3-4 renal failure;
• Massive muscle destruction in muscular dystrophy;
• A common inflammatory process in the muscles (generalized myositis);
• Syndrome of positional or prolonged compression of large muscle masses. This group of causes also includes reperfusion syndrome, which forms after the resumption of blood circulation in the extremities, the vessels of which were blocked by blood clots;
• Leptospirosis and other severe infections.

Important to remember! Blood creatinine is one of the most important diagnostic criteria for assessing the functional abilities of the kidneys. Therefore, in practice, we most often encounter precisely this reason for its increase!

Low creatinine: causes of decrease and manifestations

Reduced creatinine is rarely detected in studies. It is typical for people with problematic metabolism, in particular with protein metabolism. The reasons for the decreased performance are:

• Anemia.
• Atrophy of muscle tissue in bedridden patients.
• A diet without protein products.
• Leukemia.
• Liver diseases.
• Malignant tumors.

Patients feel muscle weakness and frequent dizziness. Their performance and memory decrease.

What negatively affects the results of the study?

Unreliable results are obtained if blood sampling was performed incorrectly (blood was taken too quickly with a thin needle). Distortion of the analysis results occurs when:

• The patient has predominantly muscle mass. The results will be inflated, but there will be no problems with the kidneys.

• On the eve of diagnosis, medications were taken (Cefazolin, ascorbic acid).

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The analysis is carried out taking into account the individual characteristics of the patient’s body.

Methods for detecting creatinine

There are 3 ways to determine creatinine levels, each of which is different in its information content.

1. Biochemistry of blood. Increased results suggest that the kidneys are affected by a pathological process. Reduced data favor muscle dystrophy.
2. Clearance of the substance. The method is based on the speed at which blood passes through the kidneys. The following ratio is recorded: enzymes in urine to blood volume. It is believed that the analysis most reliably reflects the patient’s health picture. The material for the study is daily urine.
3. The ratio of 2 substances to each other: nitrogen to creatinine. This proportion helps determine the degree of dehydration.

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What is creatinine?

The substance arises as a result of the breakdown of energy in various organs. Its location is in the muscles. Then it enters the bloodstream, through which it enters the kidneys. Excretion occurs in the urine.

Creatinine is a source of creatine (about 2 g per day). The latter belongs to nitrogen-containing structures and is necessary for the production of ATP energy. In normal amounts, creatine is not harmful: it provides muscles with energy and accelerates their recovery. In other cases, the substance leads to kidney dysfunction and weakens bone tissue.

Several factors influence creatinine levels:

• Floor.
• Race.
• Age.
• Diet.
• Weight category.
• Absence or presence of inflammatory processes.

With rare exceptions, muscle mass changes quickly, and therefore the creatinine content is a more or less stable value.

3.How to measure creatinine clearance?

Glomerular filtration rate reflects the functioning of the kidneys. If the kidneys begin to function poorly, then creatinine clearance also decreases.

There are two main ways that doctors use creatinine to measure kidney function:

• Daily urine analysis, in which all the urine in one day is collected in a special container;
• Glomerular filtration rate can be measured using a one-time blood test, the results of which are inserted into a special formula for calculation.

Blood tests are used much more often because... it is more convenient.

Options for reducing creatinine

If the concentration of the substance has increased slightly, and this was caused by minor changes in the body, then the situation can be corrected with the help of:

1. Nutrition corrections. Add lean meat (turkey, rabbit) to the menu, eating it three times a week. To normalize digestion, porridge (oatmeal, millet) is suitable.
2. Proper drinking regime. You need to take at least 2 liters of plain water per day.
3. Decreased physical activity.

If the cause of deviation from the norm in creatinine is kidney disease, then specialists should take care of the therapy.

How to lower creatinine

Creatinine can be effectively reduced only by eliminating the cause of its increase and correcting lifestyle. To do this you need:

1. It is imperative to conduct a thorough diagnosis to determine the condition of internal organs and muscle tissue;
2. For long-term and persistent hypercreatininemia, hospitalization in medical institutions of a certain profile is indicated, where treatment will be prescribed depending on the disease and cause;
3. Selection of proper nutrition. Protein foods of animal origin and fats, salt, marinades, smoked foods, seasonings, whole milk and alcohol are almost completely excluded. The diet is enriched with vegetable oils, vegetables and fruits;
4. Correction of the amount of fluid consumed. If creatinine is high due to renal pathology, water intake is minimized. In all other cases, high-quality water consumed in the right quantity will help reduce this indicator;
5. Correct motor mode. Adjusted depending on the general condition of the person;
6. Traditional medicine: various mixtures of medicinal herbs and plants, rice water;
7. Taking medications that affect protein metabolism (lespefan, ketosteril, lespinefril);
8. Methods of extracorporeal detoxification and hemodialysis (artificial kidney). An extreme measure required if creatinine is elevated to critical levels.

Creatinine is a reliable indicator of the functional abilities of internal organs. Its assessment and correction should be carried out exclusively by specialists.

Creatinine decreased

Conditions in which a decrease in plasma creatinine levels is recorded are extremely rare. Their appearance indicates a disruption of metabolic processes, accompanied by profound disorders of protein metabolism in the body in general, or isolated in muscle tissue. If hypercreatinemia mainly depends on the functional capacity of the kidneys, then in the case of hypocreatinemia (decrease in creatinine level), their condition does not play a role. Consequently, the main mechanism should be such a depletion of energy reserves in the body that protein resources, which are most abundant in the muscles, are used to repay them. A decrease in creatine phosphate reserves naturally leads to a decrease in the concentration of its metabolites in the blood, which is creatinine.