Creatinine Test

What is Creatinine?

Creatinine is one of the body’s waste products. It is produced mostly during the normal breakdown of muscle tissue and less so when protein in food is digested. Creatinine is released into the bloodstream. It is filtered from the blood by your kidneys and removed from the body in urine.

Creatinine is not the same as creatine. Creatinine is produced from creatine as the muscles use energy to provide movement. It is a waste product that builds up in the blood if the kidneys are not working properly.

Can I buy a Creatinine test online?

Yes. The Online Clinic offers the creatinine test, which includes the eGFR calculation.

What is a Creatinine test?

The creatinine test measures the concentration of creatinine in the blood. The test assesses kidney function, i.e., how well the kidneys are filtering waste products from the blood.

The creatinine test is done on its own but frequently it is part of a routine blood test or a panel test such as the Basic Metabolic Panel and Comprehensive Metabolic Panel. The creatinine concentration measures how much creatinine is currently in the blood, with low levels better than high. However, on its own, blood creatinine level is not a good way to assess a person’s kidney function. This is because the amount of creatinine produced is influenced by factors such as muscle mass, diet, age, and hydration. Creatinine blood levels are therefore often used in calculations, including those calculating the estimated glomerular filtration rate (eGFR) and creatinine clearance (CrCl).

The creatinine test done by The Online Clinic includes the calculation of eGFR, which is a more accurate measurement of kidney function than the creatinine level in blood or urine. The eGFR calculates the volume of blood the kidneys filter waste products (such as creatinine) per minute, with high rates better than low. eGFR can indicate the seriousness of a kidney disease, and can be calculated using serum creatinine level, age, and sex.

CrCl calculates the rate at which the kidneys clear (filter) the blood of creatinine, with high rates better than low. However, eGFR is considered a more accurate calculation than CrCl because CrCl results can be false in anyone who has a muscle mass that is very different from the average for that person’s age, sex and sometimes ethnicity. For example, creatinine clearance shows high blood creatinine levels in individuals who have a large muscle mass (e.g., from weight-lifting) and low creatinine levels in those who have lost muscle (e.g., due to age or illness).

How long do results take for the Creatinine test?

Results are back within 1 day of the sample arriving at our laboratory. A doctor will interpret your results for you as part of the service.

Why is a Creatinine test important?

A creatinine test is used:

• To assess kidney health and check that the kidneys are working well, which can prevent future complications of kidney disease.
• As part of the routine care of people who seem healthy or of people at high risk of chronic kidney disease (CKD) such as those with diabetes and hypertension.
• In the diagnosis of kidney disease.
• To monitor kidney function and predict disease progression in people with CKD and other kidney problems.
• To monitor the effectiveness of medications for kidney conditions, allowing assessment of whether the medication or its dosage needs changing to prevent over- or under-treatment.

Who should have their Creatinine level tested?

The creatine test can be used to investigate individuals:

• Who have abnormal creatine levels at a routine check-up or have previously had abnormal creatine levels.
• Who regularly take medicines known to affect the kidneys.
• At high risk of CKD, including those with diabetes, hypertension, or heart disease; have a family history of kidney disease, obesity, an unhealthy diet, or poor sleep habits; or who smoke, overuse painkillers, or are of older age.
• With signs and symptoms of kidney disease, including tiredness, changes in frequency of urination/amount and colour of urine, swelling in the ankles, feet and/or hands, breathlessness, muscle cramps, loss of appetite, weight loss, and nausea/vomiting.
• Who have kidney disease, a kidney transplant, or only one kidney.

How to test for Creatinine?

The creatinine test measures the level of creatinine in a small sample of blood. Either a healthcare professional collects the blood sample from a vein in your arm at a clinic or you collect the blood sample from a little finger at home using the contents of a fully-equipped pack provided by The Online Clinic. Collection is easy, with blood drops collected in a collection tube up to the top line marked on the tube. The collection tube is placed in a packing wallet and posted to the laboratory for analysis. The test results are sent to a doctor at The Online Clinic who will explain whether you are at risk of kidney problems or the status of any kidney problems that you may have.

What are normal Creatinine test results?

After one month of age, blood serum creatinine increases with age. For the average healthy person 20 to 65–70 years of age, serum creatinine level remains stable with a normal reference range of 0.60–0.2 mg/dL for men and 0.5–1.0 mg/dL for women. Above the age of 65–70 years, serum creatinine starts to slowly increase with a normal reference range of approximately 0.7–1.3 mg/dL for men and 0.6–1.1 mg/dL for women. Reference range values may vary depending on the methods used by the analysing laboratory to measure creatinine in serum and to calculate eGFR.

Kidney problems are generally reflected in a rise in creatinine levels. However, blood creatinine levels can be within the normal reference range in the early stages of CKD when the kidneys are damaged but are able to compensate and remove waste products effectively. Levels rise once the kidney condition becomes more serious, and kidney function is impaired.

A high blood creatinine level (and therefore low eGFR) may be sign of kidney disease, kidney failure, or kidney injury (e.g., caused by infections, poor kidney blood supply, urinary system blockage), or a condition affecting the kidneys (e.g., diabetes or heart disease). A low blood creatinine level (and therefore high eGFR) is typically a sign of another condition, such as a muscle or nerve disorder and liver cirrhosis.

However, other factors not related to kidney health can result in creatinine levels (and eGFR) to be higher or lower than expected. Factors unrelated to kidney conditions leading to high creatinine levels (and low eGFR) include a high muscle mass, eating too much meat, dehydration, intense exercise, creatine supplements, and certain medicines (e.g., cimetidine, fenofibrate, ibuprofen and some antibiotics, antivirals, chemotherapies, and antihypertensives). Those factors leading to lower creatinine levels (and high eGFR) include a low muscle mass, muscle wasting (due to aging, malnutrition or illness), limb amputation, a plant-based diet, and pregnancy.

How to maintain normal Creatinine levels

Maintaining normal creatinine levels depends on supporting kidney function and minimising the unnecessary breakdown of muscle. The main ways to achieve this is to include eating a balanced diet with moderate amounts of protein, staying hydrated, controlling underlying conditions such as diabetes and hypertension, smoking cessation, moderating alcohol intake and amount of intense exercise, and avoiding supplements and, where possible, non-prescription medications that affect the kidneys (speak to a doctor before stopping prescription medicines).

References

Ávila M, Mora Sánchez MG, Bernal Amador AS, et al. The Metabolism of Creatinine and Its Usefulness to Evaluate Kidney Function and Body Composition in Clinical Practice. Biomolecules. 2025;15:41. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC11764249/

Cleveland Clinic. Creatinine clearance test. Last updated 27 Nov 2023. Available from: https://my.clevelandclinic.org/health/diagnostics/16380-creatinine-clearance-test Accessed 15 May 2026.

Delanaye P, Cavalier E, Pottel H. Serum Creatinine: Not So Simple! Nephron. 2017;136:302-308. Available from: https://pubmed.ncbi.nlm.nih.gov/28441651/

MedlinePlus. Creatinine test. Last updated 5 Dec 2023. Available from: https://medlineplus.gov/lab-tests/creatinine-test/ Accessed 15 May 2026.

National Kidney Foundation. Creatinine. Updated 2023, June 01. Available from: https://www.kidney.org/kidney-topics/creatinine Accessed 13 May 2026.

Shahbaz H, Rout P, Gupta M. Creatinine Clearance. [Updated 2024 Jul 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan–. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544228/

Ubie Doctors note. Understanding Creatinine Levels: Kidney Function After 65. 2026, Jul 2. Available from: https://ubiehealth.com/doctors-note/creatinine-levels-kidney-function-after-65-73-tips21e5 Accessed 15 May 2026.