Creatinine Test: Purpose, Preparation, Normal Range and Results

Creatinine is a waste material that is produced during the normal wear and tear of the muscles of the body. Your muscles have a high-energy molecule, called creatine phosphate. Creatinine is the by-product of creatine phosphate, which is produced at a constant rate and cleared from the blood by the kidneys. Each one of us has creatinine in the blood. If the creatinine clearance is decreased, it results in increased blood (or serum) creatinine. A rise in serum creatinine is an indicator of kidney impairment and creatinine serum test would help you find that out.

What is Creatinine Serum Test?

The creatinine serum test is a blood test that measures the level of creatinine in your blood. It's part of a group of tests that are used to find out how well your kidneys are functioning (renal function tests). This blood test is usually done when your doctor thinks that your body isn't getting rid of the waste properly.

Indications of a Creatinine Serum Test

The creatinine serum test is important because it can give doctors various indications, such as:

- To measure the level of creatinine in the blood.

- To determine how well the kidneys are functioning.

- To diagnose kidney disease.

- To monitor kidney function during and after treatment for kidney disease.

- Check whether your kidneys are facing the side effects of the drugs you take.

When do you need a creatinine serum test?

Your healthcare specialist might prescribe you this test if you have symptoms of kidney disease, including-

• Anorexia (an eating disorder characterized by low weight and food restrictions)
• Frequently painful urination
• Foamy or bloody urine

What is The Normal Level of Creatinine?

The normal range of creatinine varies with age, race, gender, and body size.
In general,

• The normal range of creatinine for adult men: 0.74 to 1.35 mg/dL
• The normal range of creatinine for adult women: 0.59 to 1.04 mg/dL

In general, while muscular young or middle-aged adults may have more creatinine in their blood than the general population, elderly people may have lower creatinine. For people who are dealing with malnutrition, severe weight loss, and chronic conditions, creatinine levels might be lower than other people of the same age group, owing to a reduction in muscle mass over time.

When Do You Need a Creatinine Serum Test?

You may need to get your creatinine levels tested if you have symptoms of kidney disease, are at risk of getting kidney problems, or want to check your kidney health.

The following symptoms can be suggestive of health issues related to the kidneys: 

-Fatigue, not attributed to any other cause
-Puffiness around the eyes
-Swelling in your feet and/or ankles
-Frequent and painful urination
-Foamy or bloody urine

Your risk of getting kidney disease is higher if you have:

-A family history of kidney disease
-Type 1 or type 2 diabetes
-High blood pressure

Is knowing Creatinine Values Tell my Doctor if my Kidneys are Working Properly?

Your doctor needs to look at how much creatinine is in your blood along with some other important parameters as well. The reason is creatinine levels in your blood can be affected by your age, race, gender, and body size. The best way to know if your kidneys are functioning well is to look at your glomerular filtration rate (GFR) and creatinine. GFR is a measure of how much blood passes through the tiny filters of the kidneys (glomeruli) each minute. If the kidneys are damaged, they shall pass lesser blood to get filtered. Please note that creatinine is considered a late marker of acute kidney injury because kidney function is decreased by almost 50% before a rise in serum creatinine is observed.

What Do Raised Creatinine Levels Indicate?

Any health condition that impairs the function of your kidneys is likely to cause a spike in creatinine serum levels. It is equally important to identify whether the condition and process leading to kidney dysfunction are recent or chronic. While recent elevations may be more easily reversed and treated, chronic conditions might be difficult to deal with and demand special care.

The most common causes of chronic kidney disease include

-High blood pressure
-Diabetes.

Other causes of elevated blood creatinine levels are:

• Consumption of a large amount of meat in the diet
• Certain drugs (for example, cimetidine)
• Kidney infections, abnormal muscle breakdown (rhabdomyolysis), and urinary tract obstruction.

How Do You Prepare for a Creatinine Serum Test?

There are a few things you can do to prepare for a creatinine serum test. First, it is important to fast for at least 8 hours before the test. Second, avoid strenuous exercise for 24 hours before the test. Third, avoid taking any medications that could interfere with the test results. Finally, be sure to drink plenty of fluids to keep your body hydrated.

How is Creatinine Serum Test Performed?

A Creatinine Serum Test is a blood test that measures the levels of creatinine in your blood. If your kidneys are not working properly, the levels of creatinine in your blood will increase.

The test is usually ordered when your doctor suspects that you may have kidney disease. It can also be ordered to check how well your kidneys are working after a kidney transplant.

• Blood test: a small sample of blood will be taken from a vein in your arm. The sample will then be sent to a laboratory for analysis.
• Urine test: You have to collect your urine sample and submit it to the laboratory for analysis.

Result of a Creatinine Serum Test

The result of a creatinine serum test is used to determine the following-

Serum Creatinine Level

The amount of creatinine in your bloodstream and the creatinine filtration rate in your body should be stable, if not constant. Serum creatinine level is the amount of creatinine present in your blood and is measured in milligrams per deciliter (mg/dL).

The average serum creatinine level ranges between 0.74 - 1.35 mg/dL (65.4 - 119.3 micromoles/L) in adult men, while it should lie between 0.59 - 1.04 mg/dL (52.2 - 91.9 micromoles/L) in healthy adult women. 

An increased serum creatinine level is indicative of poor kidney health.

Glomerular Filteration Rate (GFR)

The creatinine serum test result determines your glomerular filtration rate (GRF). The glomerular filtration rate is the volume of plasma filtered by the glomeruli per second. GFR is used to check whether the kidneys are functioning correctly.

Since blood creatinine levels vary from person to person, the GFR can give a more accurate indication of renal function. It is calculated based on several factors, including serum creatinine count, age, gender, etc. A GFR below 60 points toward renal disorders.

Creatinine Clearance

The removal of creatinine from the bloodstream by the kidneys, which is later excreted as urine, is measured as creatinine clearance. 

The creatinine measurement in 24-hour urine and blood samples is typically used to calculate creatinine clearance. Therefore, it's essential to collect these samples at the proper time.

Creatinine clearance is measured as milliliters of creatinine per minute per body surface area (mL/min/BSA). Men's typical creatinine clearance range from 19 - 75 lies between 77 - 160 mL/min/BSA.

Creatinine clearance in women varies from one age group to others follows-

• 18 - 29 years: 78 - 161 mL/min/BSA

• 30 - 39 years: 72 - 154 mL/min/BSA
• 40 - 49 years: 67 - 146 mL/min/BSA
• 50 - 59 years: 62 - 139 mL/min/BSA
• 60 - 72 years: 56 - 131 mL/min/BSA

Low creatinine clearance indicates poor kidney function and renal disorders.

Albumin/Creatinine Ratio

The albumin/creatinine ratio is yet another way to evaluate the urine creatinine count.

Albumin is a protein in the blood, essential to prevent it from leaking through the veins and arteries. There should be little or no albumin in the urine, as healthy kidneys often do not filter it out of the blood. 

The albumin/creatinine ratio quantifies a urine sample's albumin to creatinine ratio. It is measured as the ratio of albumin in milligrams (mg) to creatinine in grams (g). The results are typically less than 17 mg/g in healthy adult men, while they should fall below 25 mg/g in healthy adult women.

A higher albumin/creatinine ratio indicates diabetic nephropathy, also known as diabetic kidney disease.

What Should I Do After Getting My Creatinine Serum Test Results?

It is important to tell your doctor about any medicines you are currently taking, both prescription and over-the-counter. Some drugs, like cimetidine, chemotherapy drugs, cephalosporin antibiotics, may increase your creatinine levels and impact your test results. Your doctor may take this into consideration when interpreting your lab test results.

Get Geared up for a Better Kidney Health

Your kidneys are vital organs that help remove toxic body wastes and optimize your health. Along with getting your serum creatinine and kidney function checked from time to time, keep yourself hydrated and include fresh, leafy vegetables in your diet. Being physically active also helps your kidneys stay healthy and well-functioning. 

Conclusion

The creatinine serum test is a test that is used to detect kidney dysfunction. The kidneys are responsible for filtering blood and ridding the body of waste products, so if they are not working properly, it can lead to a buildup of creatinine in the blood. This test is often ordered as part of a workup for someone who is experiencing kidney failure. This test can also be used to determine the cause of high creatinine levels that are a result of dehydration.