What is the Difference Between Urine Creatinine and Serum Creatinine

Creatinine is a non-protein nitrogenous compound produced by the breakdown of creatine in muscle that usually supplies energy to the muscles. Creatinine is found in serum, plasma, and urine. It is excreted by glomerular filtration by kidneys at a constant rate and in the same concentration as in plasma.

The key difference between urine creatinine and serum creatinine is their source. Urine creatinine is the creatinine that is filtered out by the kidneys into the urine, while serum creatinine is the creatinine in the blood that comes from the muscles.

CONTENTS

1. Overview and Key Difference
2. What is Urine Creatinine 
3. What is Serum Creatinine
4. Similarities – Urine Creatinine and Serum Creatinine
5. Urine Creatinine vs Serum Creatinine in Tabular Form
6. Summary – Urine Creatinine vs Serum Creatinine
7. FAQ – Urine Creatinine and Serum Creatinine

What is Urine Creatinine?

Creatinine is a waste product that is filtered out by glomerular filtration by kidneys at a constant rate. A creatinine urine test measures the amount of creatinine in the urine. It is usually performed to see how well the kidneys are working.

Creatinine is removed by the human body entirely by the kidneys. If the kidneys’ function is not normal, the creatinine level in the urine changes. Low urine creatinine indicates liver or muscle problems, while high urine creatinine indicates kidney disease. This test is used to evaluate how well the kidneys are working as part of the creatinine clearance test and to provide information on other chemicals in the urine, like albumin or other proteins. Urine creatinine levels can range from 500 to 2000 mg/day (in 24-hour urine collection). Furthermore, there are no risks with this test.

What is Serum Creatinine?

Serum creatinine is a waste product in the blood that comes from the muscles by the breaking down of creatine. Kidneys filter creatinine out of the blood through the urine. The serum creatinine level can be measured based on a blood test.  Therefore, the serum creatinine test measures the amount of creatinine in the blood.

The serum creatinine level goes up when the kidneys are not working well. Therefore, this test tells how well the kidneys work well and helps diagnose kidney diseases. In general, a normal level of creatinine in serum is 0.7 – 1.3 mg/dL for males and 0.6 – 1.1 mg/dL for females. The risks that are associated with this test include slight bruising at the site of blood drawn for the test.

Similarities Between Urine Creatinine and Serum Creatinine

1. Urine creatinine and serum creatinine are creatinine that are present in two different body fluids in the body.
2. Both are very important for detecting kidney functioning.
3. Both can be part of the creatinine clearance test.
4. They can be measured by respective tests in mg/dL.
5. Higher levels in both mean kidneys are not working properly.

Difference Between Urine Creatinine and Serum Creatinine

Definition

1. Serum creatinine is a waste product in the blood that comes from the muscles when creatine is broken down.
2. Urine creatinine is the creatinine that kidneys filter out of the blood through the urine.

Measured by

1. Serum creatinine is measured by a blood test.
2. Urine creatinine is measured by a urine test.

Normal Level

1. Urine creatinine levels can range from 500 to 2000 mg/day (in 24-hour urine collection).
2. Serum creatinine level is 0.7 – 1.3 mg/dL for males and 0.6 – 1.1 mg/dL for females.

Function

1. Serum creatinine tests are used to evaluate how well the kidneys are working, as part of the creatinine clearance test and to provide information on other chemicals in the urine like albumin or other proteins.
2. Urine creatinine is used to test how well the kidneys are working and helps diagnose kidney diseases.

Risks of Test

1. There are no risks with the serum creatinine test.
2. There might be slight bruising at the site where blood was drawn for a urine creatinine test.

The following table summarizes the difference between urine creatinine and serum creatinine.

Summary – Urine Creatinine vs Serum Creatinine

Creatinine is a waste product produced from the creatine of the muscles and can be present in serum, plasma and urine. Urine creatinine and serum creatinine are creatinine present in two different body fluids in the body. Serum creatinine is a waste product in the blood that comes from the muscles by the breaking down of creatine while urine creatinine is the creatinine that kidneys filter out of the blood through the urine. This is the basic difference between urine creatinine and serum creatinine.

FAQ: Urine Creatinine and Serum Creatinine

1. What is the serum creatinine normal range?

• The normal range for serum creatinine is 0.74 to 1.35 mg/dL for adult males (65.4 to 119.3 micromoles/L) and 0.59 to 1.04 mg/dL (52.2 to 91.9 micromoles/L) for adult females.

2. What serum level of creatinine is concerning?

• High serum creatinine levels can indicate a range of underlying health conditions including kidney infection and kidney failure. Doctors typically consider high creatinine levels to be above 1.2 milligrams per deciliter (mg/dL) for males and 1.0 mg/dL for females.

3. What is normal urine creatinine?

• Normal urine creatinine values generally range from 955 to 2,936 milligrams (mg) per 24 hours for males and 601 to 1689 mg per 24 hours for females. Creatinine values that fall outside the normal range may be an indication of kidney disease, such as kidney infection.

4. What does low urine creatinine mean?

• Low creatinine levels could indicate a problem with muscles or the liver.  It also may be due to something less serious, such as reduced muscle mass in older adults, drinking too much water or pregnancy.

5. What does a high urine creatinine mean?

• A higher urine creatinine may be a sign of kidney disease. It can be a complication of diabetes called diabetic nephropathy or diabetic kidney disease.

Reference:

1. Cindy, Seiwert. “Urinary System.” Human Biology, Goodwin University.
2.“Creatinine.” National Kidney Foundation.

Image Courtesy:

1. “Urine samples of varying colour and clarity” By Lehmann R. From bedside to bench-practical considerations to avoid pre-analytical pitfalls and assess sample quality for high-resolution metabolomics and lipidomics analyses of body fluids. Anal Bioanal Chem. 2021 Sep;413(22):5567-5585. doi: 10.1007/s00216-021-03450-0. Epub 2021 Jun 22. PMID: 34159398; PMCID: PMC8410705. (CC BY 4.0) via Commons Wikimedia
2. “Hands of Person Holding a Glass Test Tube with Blood” (CC0) via Pexels

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