Creatine, Kidney & Liver Health: Blood Tests Explained

By Jelena Savic, BHSc (Naturopathy) · Published 28 September 2026 · 11 min read

Understanding creatine, organ health and blood tests

A blood test after a hard training block can be confusing. The report may mention creatinine or creatine kinase, while the supplement tub says creatine. The names look related, but they do not measure the same thing.

This article separates those terms, explains why supplementation may influence one kidney-function marker, and shows why a CK result must be interpreted in clinical context. It is educational only. A single laboratory result cannot diagnose kidney, liver or muscle disease, and supplement advice should not replace assessment by a healthcare professional. ^5,6,7

Creatine vs creatinine vs creatine kinase

Glomerular filtration rate (GFR): The rate at which the kidneys filter blood. In routine care it is commonly estimated, rather than measured directly.

eGFR: An estimated GFR calculated from biomarkers such as creatinine, cystatin C or both. The US National Institute of Diabetes and Digestive and Kidney Diseases notes that eGFR is an estimate, and trends are often more informative than a single value. ⁶

Is creatine bad for your kidneys in healthy adults?

The strongest current summary is population-specific. A 2025 systematic review and meta-analysis reported a modest increase in serum creatinine with creatine supplementation but no statistically significant difference in GFR compared with control groups. The authors interpreted the creatinine change as likely reflecting metabolic turnover rather than impaired filtration. ²

A 2019 systematic review and meta-analysis likewise concluded that supplementation did not induce renal damage in the amounts and durations studied. ³ In a small randomised trial, approximately 10 g per day for three months did not produce evidence of renal dysfunction in healthy men undertaking aerobic training when cystatin C and other measures were assessed. ^4,8

This evidence does not establish that creatine is safe for everyone, at every intake, indefinitely, or in people with kidney disease. It also does not make a particular intake "kidney-safe" for an individual. Dose, health status, other supplements, medicines and the reason for testing all matter.

Why creatinine can rise after starting creatine

Creatinine is one routine input used to estimate kidney filtration. Because creatine can increase the pool from which creatinine is formed, supplementation may produce a small rise in serum creatinine even when measured or independently estimated filtration has not worsened. The 2025 meta-analysis found this pattern across the available evidence. ²

That does not mean every raised creatinine result in a person using creatine should be dismissed. Creatinine is affected by several non-GFR factors, and an abnormal result may still require follow-up.

When greater precision is needed, the clinician may consider additional assessment. NIDDK states that using both creatinine and cystatin C provides a more accurate eGFR estimate than creatinine alone. KDIGO recommends combined creatinine-cystatin C estimation when cystatin C is available for adults at risk of chronic kidney disease. ^6,7

What creatine kinase blood tests measure

A creatine kinase test measures the amount of CK enzyme in blood. Most CK is in skeletal muscle; smaller amounts are found in heart muscle and brain tissue. When those cells are stressed or damaged, more CK can enter the bloodstream. CK testing is used to help investigate or monitor muscle injury and certain muscle diseases. ⁵

Hard or unfamiliar exercise can increase CK, so recent training is important context. Medicines, injuries and medical conditions can also affect the result.

There is no single consumer-safe answer to "what level of creatine kinase is dangerous?" Laboratories may use different reference ranges, and clinical urgency depends on more than the number. A markedly abnormal value alongside severe muscle pain or weakness, dark urine, reduced urine output or feeling acutely unwell needs prompt medical assessment. MedlinePlus notes that rhabdomyolysis is a rapid breakdown of muscle tissue that can lead to kidney failure. ⁵

Does taking creatine itself raise CK?

CK and creatine are biologically related to muscle energy systems, but they are not interchangeable tests. Current authoritative testing guidance identifies exercise, muscle injury and several medical or medicine-related causes of raised CK. It does not establish that routine creatine supplementation by itself is the cause of an elevated CK result. ⁵

What the evidence says about creatine and liver health

The liver is included in many consumer safety questions, and the direct human evidence base is smaller than the kidney literature used above, but two dedicated sources add useful context. A 21-month study of Division I college football players who supplemented with creatine found no significant differences in liver enzymes or other clinical-health markers compared with non-supplementing teammates. ⁹ Separately, a 2023 cross-sectional analysis of US national survey data found that higher dietary creatine intake was not associated with a greater risk of liver fibrosis, cirrhosis or hepatic steatosis. ¹⁰

The ISSN position stand separately reports that short- and long-term creatine supplementation was well tolerated in the populations and protocols it reviewed, but that broad safety summary should not, on its own, be read as a guarantee of liver safety for every person. ¹

Who should be cautious with kidney or liver concerns

• Diagnosed kidney or liver disease.
• Unexplained abnormal kidney, liver or muscle-enzyme results.
• Medicines that may affect kidney function, liver function or muscle tissue.
• Symptoms that could indicate acute illness.
• Pregnancy or breastfeeding, or another health circumstance requiring individual advice.

Do not stop prescribed medicine or alter a supplement solely because of an online article or one isolated result. A clinician can consider your history, symptoms, laboratory trend, medicines, training and supplement use together.

What to tell your doctor before a blood test

1. Supplements you use, including creatine and the labelled amount.
2. Prescription and non-prescription medicines.
3. Recent intense, long or unfamiliar exercise.
4. Previous kidney, liver or muscle conditions.
5. Recent illness, dehydration or symptoms.
6. Earlier results that may help show a trend.

Do not stop creatine before testing unless the clinician who ordered the test advises you to do so. The appropriate preparation depends on the tests ordered and the clinical question. For general guidance on preparing for a pathology test and questions to ask your doctor, see Pathology Tests Explained, a consumer resource run by a consortium of Australasian pathology and laboratory-medicine bodies including the RCPA and AACB. ¹¹

How this article connects to the Musashi creatine guide

For broader education on creatine side effects and digestive safety, read Creatine Side Effects, Safety & Digestive Health. The Musashi creatine pillar guide and other related articles will be linked here once each page is published.

Key takeaways about creatine and kidney or liver health

• Creatine, creatinine and creatine kinase are different and should not be interpreted as the same marker.
• Creatine may modestly increase serum creatinine without evidence of reduced GFR in the studied healthy populations.
• A raised creatinine or CK result still requires clinical context and should not be self-diagnosed.
• CK commonly reflects muscle stress or damage; recent intense exercise can affect the result.
• Evidence about liver outcomes is less direct and does not support blanket safety claims.
• Tell your healthcare professional about supplements, medicines and recent training before interpreting blood tests.

Frequently asked questions about creatine, kidneys and blood tests

Is creatine bad for your kidneys?

In the healthy adults and studied protocols included in systematic reviews, creatine supplementation did not show impaired kidney filtration, although serum creatinine may rise modestly. This finding does not cover everyone, every intake or pre-existing kidney disease. People with kidney concerns or abnormal results need individual medical advice. ^2,3

Why did my creatinine come back high after starting creatine?

Creatine supplementation can modestly raise serum creatinine because creatinine is related to creatine turnover. That may influence creatinine-based eGFR without proving kidney damage, but an abnormal result should not be dismissed. Tell your clinician about supplementation, recent exercise and medicines so they can interpret the result and decide whether further assessment is needed. ^2,6

What is creatine kinase, and is it different from creatine?

Yes. Creatine kinase, or CK, is an enzyme found mainly in skeletal muscle, while creatine is a compound involved in rapid energy transfer and is also used as a supplement. CK can rise with muscle stress or damage, including extreme exercise, and the result requires clinical context. ^1,5

Should I stop creatine before a blood test?

Do not stop creatine solely on the basis of general online advice. Tell the clinician who ordered the test that you use it and follow their preparation instructions. Supplement use, recent hard exercise, medicines and the specific tests ordered can all affect how results are interpreted. ^5,6

References

1. Kreider, R. B., Kalman, D. S., Antonio, J., Ziegenfuss, T. N., Wildman, R., Collins, R., Candow, D. G., Kleiner, S. M., Almada, A. L., & Lopez, H. L. (2017). International Society of Sports Nutrition position stand: Safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition, 14, 18. https://doi.org/10.1186/s12970-017-0173-z
2. Kabiri Naeini, E., Eskandari, M., Mortazavi, M., Gholaminejad, A., & Karevan, N. (2025). Effect of creatine supplementation on kidney function: A systematic review and meta-analysis. BMC Nephrology, 26, 622. https://doi.org/10.1186/s12882-025-04558-6
3. de Souza e Silva, A., Pertille, A., Barbosa, C. G. R., de Oliveira Silva, J. A., de Jesus, D. V., Ribeiro, A. G. S. V., Baganha, R. J., & de Oliveira, J. J. (2019). Effects of creatine supplementation on renal function: A systematic review and meta-analysis. Journal of Renal Nutrition, 29(6), 480–489. https://doi.org/10.1053/j.jrn.2019.05.004
4. Gualano, B., Ugrinowitsch, C., Novaes, R. B., Artioli, G. G., Shimizu, M. H., Seguro, A. C., Harris, R. C., & Lancha, A. H., Jr. (2008). Effects of creatine supplementation on renal function: A randomized, double-blind, placebo-controlled clinical trial. European Journal of Applied Physiology, 103(1), 33–40. https://doi.org/10.1007/s00421-007-0669-3
5. MedlinePlus. (2023). Creatine kinase. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/creatine-kinase/
6. National Institute of Diabetes and Digestive and Kidney Diseases. (n.d.). eGFR calculators for adults and pediatrics. National Institutes of Health. NIDDK: eGFR calculators for adults and pediatrics
7. Kidney Disease: Improving Global Outcomes. (2024). KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease: Summary of recommendation statements and practice points. Kidney International, 105(Suppl. 4S), S117–S314. KDIGO 2024 CKD Guideline: summary recommendations (PDF)
8. Vilar Neto, J. O., da Silva, C. A., Meneses, G. C., Pinto, D. V., Brito, L. C., Fonseca, S. G. C., Alves, R. S., & Martins, A. M. C. (2020). Novel renal biomarkers show that creatine supplementation is safe: A double-blind, placebo-controlled randomized clinical trial. Toxicology Research, 9(3), 263–270. https://doi.org/10.1093/toxres/tfaa028
9. Kreider, R. B., Melton, C., Rasmussen, C. J., Greenwood, M., Lancaster, S., Cantler, E. C., Milnor, P., & Almada, A. L. (2003). Long-term creatine supplementation does not significantly affect clinical markers of health in athletes. Molecular and Cellular Biochemistry, 244(1–2), 95–104. https://doi.org/10.1023/A:1022469320296
10. Todorovic, N., Korovljev, D., Stajer, V., Jorga, J., & Ostojic, S. M. (2023). Creatine consumption and liver disease manifestations in individuals aged 12 years and over. Food Science & Nutrition, 11(2), 1134–1141. https://doi.org/10.1002/fsn3.3151
11. Pathology Tests Explained. (n.d.). Preparing for your tests and questions to ask your doctor. Retrieved 27 August 2026, from Pathology Tests Explained: preparing for your tests

The information in this article is for educational purposes only and is not intended as medical advice. Always read the label and follow the directions for use. If symptoms persist, consult your healthcare professional. Musashi products are formulated for healthy adults; consult a healthcare professional before use if you have a pre-existing medical condition, are pregnant or breastfeeding, or are taking medication.