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Creatinine and eGFR – Kidney function

Creatinine and eGFR show how well the kidneys filter the blood. eGFR is the estimated glomerular filtration rate and is the value that best describes kidney function.

What is Creatinine and eGFR?

Creatinine is a waste product from the muscles that the kidneys filter out. Based on creatinine or cystatin C, age, and gender, eGFR is calculated—a measure of how many millilitres of blood the kidneys clean per minute.

Why is Creatinine and eGFR measured in a health check?

Reduced kidney function does not produce symptoms until late. The test is particularly relevant in cases of high blood pressure, diabetes, cardiovascular disease, and during long-term use of certain medications.

High and low values

High value: High creatinine, and thus low eGFR, indicates reduced kidney function, but can also be due to dehydration or large muscle mass.

Low value: Low creatinine is seen in small muscle mass and is rarely a problem in itself.

Reference ranges differ between laboratories, sexes and ages and are stated in your result. The information here does not replace medical assessment.

How kidney function is measured in a health check

Creatinine is a waste product from muscle energy metabolism that the kidneys filter out. The test is taken in a standard blood draw, and eGFR — an estimate of how much blood the kidneys clean per minute — is calculated from creatinine, age and sex. It's eGFR that's used to describe kidney function, not the creatinine value on its own.

Since creatinine comes from muscle, the value is affected by muscle mass. A well-trained person with a lot of muscle can have higher creatinine without worse kidney function, while a person with little muscle mass can have normal creatinine despite reduced function. A large intake of meat or creatine supplements in the days before the test can also raise the value, as can marked dehydration.

Why kidney function is worth following

Reduced kidney function often causes no symptoms until a large part of the function has already been lost. A health-check blood test with creatinine and eGFR makes it possible to catch a slow decline in time and address the factors driving it.

  • High blood pressure — the most common cause of kidney impairment together with diabetes
  • Diabetes or elevated HbA1c
  • Regular use of NSAIDs (for example ibuprofen)
  • Kidney disease in the family
  • Recurrent urinary tract infections or kidney stones
  • Old age, where eGFR naturally declines slightly

How the result is interpreted

A single, slightly reduced eGFR rarely means disease. Dehydration, a protein-rich meal or hard exercise can explain it, and a repeat test after a few weeks often shows a normal value. Chronic kidney disease is defined by reduced function on repeated measurements over at least three months.

For a more complete picture, creatinine is sometimes supplemented with cystatin C, which isn't affected by muscle mass, and with a urine test to see if albumin is leaking out. In a health check, kidney function is best interpreted together with blood pressure, HbA1c and blood lipids, since the same risk factors drive both cardiovascular disease and kidney impairment.

What you can do yourself

Well-managed blood pressure, stable blood glucose, moderate salt and alcohol consumption, adequate fluid intake and sparing use of over-the-counter anti-inflammatory medication are the most important measures for protecting the kidneys. If you've once had a reduced eGFR, an annual check is reasonable, ideally in the same health check as blood-pressure-related markers.

Frequently asked questions about Creatinine and eGFR

What is the difference between creatinine and eGFR?

Creatinine is the measured substance in the blood, while eGFR is a calculation of the kidneys' filtration capacity based on creatinine or cystatin C along with age and gender. eGFR is easier to interpret.

Why is eGFR measured with both creatinine and cystatin C?

Creatinine is affected by muscle mass and diet; cystatin C is not. In cases of very large or small muscle mass, cystatin C provides a more accurate picture, and the combination is safest.

Do protein supplements affect the test?

High intake of meat or protein supplements and hard training can temporarily raise creatinine. Therefore, avoid both for 24 hours before sampling.

Can creatine supplements affect the test?

Yes. Creatine and a large meat intake can raise creatinine without kidney function actually being worse. It's a good idea to pause the supplement for a few days before the test.

What does eGFR mean?

eGFR is an estimate of how much blood the kidneys filter per minute, calculated from creatinine, age and sex. It's used to grade kidney function.

Does a reduced eGFR always need to be investigated?

A single, slightly reduced value is usually rechecked. Persistent reduction, or reduction together with high blood pressure or diabetes, should be assessed by a doctor.

Health checks that include Creatinine and eGFR

Creatinine and eGFR is included in 11 of Labkollen's health checks. Analysis name in the result: Kreatinin, eGFR (Cystatin C), eGFR (Kreatinin).

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Guides covering Creatinine and eGFR

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Responsible for the content: Mathias Khemiri, Oftamed Sverige AB.

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